[chore]: MASSIVE refactor + more vulkan bs

16 files changed, 1402 insertions, 0 deletions

diff --git a/src/platform/opengl/opengl_framebuffer.cpp b/src/platform/opengl/opengl_framebuffer.cpp
new file mode 100644
index 0000000..1624439
--- /dev/null
+++ b/src/platform/opengl/opengl_framebuffer.cpp
@@ -0,0 +1,246 @@
+#include "opengl_framebuffer.h"
+#include "core/log.h"
+
+#include <glad/glad.h>
+
+namespace Donut
+{
+    namespace Utils
+    {
+        static GLenum TextureTarget(bool multisampled)
+        {
+            return multisampled ? GL_TEXTURE_2D_MULTISAMPLE : GL_TEXTURE_2D;
+        }
+
+        static void bind_texture(bool multisampled, uint32_t id)
+        {
+            glBindTexture(TextureTarget(multisampled), id);
+        }
+
+        static void CreateTextures(bool multisampled, uint32_t* out_id, uint32_t count)
+        {
+            // glCreateTextures is 4.5 DSA; macOS caps at 4.1. Callers bind each
+            // texture (with the correct target) before use.
+            glGenTextures(count, out_id);
+        }
+
+        static void AttachColorTexture(uint32_t id, int samples, GLenum internal_format, GLenum format, uint32_t width, uint32_t height, int index)
+        {
+            bool multisampled = samples > 1;
+            if (multisampled)
+            {
+                glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, samples, internal_format, width, height, GL_FALSE);
+            }
+            else
+            {
+                // Integer color formats require an integer pixel type even when
+                // data is null, or macOS's strict core profile rejects the call.
+                GLenum type = (format == GL_RED_INTEGER) ? GL_INT : GL_UNSIGNED_BYTE;
+                glTexImage2D(GL_TEXTURE_2D, 0, internal_format, width, height, 0, format, type, nullptr);
+
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+            }
+
+            glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + index, TextureTarget(multisampled), id, 0);
+        }
+
+        static void AttachDepthTexture(uint32_t id, int samples, GLenum format, GLenum attachment_type, uint32_t width, uint32_t height)
+        {
+            bool multisampled = samples > 1;
+            if (multisampled)
+            {
+                glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, samples, format, width, height, GL_FALSE);
+            }
+            else
+            {
+                // glTexStorage2D is 4.2; use mutable storage for macOS (4.1).
+                GLenum depth_format = (format == GL_DEPTH24_STENCIL8) ? GL_DEPTH_STENCIL : GL_DEPTH_COMPONENT;
+                GLenum depth_type   = (format == GL_DEPTH24_STENCIL8) ? GL_UNSIGNED_INT_24_8 : GL_FLOAT;
+                glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, depth_format, depth_type, nullptr);
+
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+            }
+
+            glFramebufferTexture2D(GL_FRAMEBUFFER, attachment_type, TextureTarget(multisampled), id, 0);
+        }
+
+        static bool IsDepthFormat(FramebufferTextureFormat format)
+        {
+            switch (format)
+            {
+                case FramebufferTextureFormat::DEPTH24STENCIL8:  return true;
+            }
+            return false;
+        }
+
+        static GLenum DonutFBTextureFormatToGL(FramebufferTextureFormat format)
+        {
+            switch (format)
+            {
+                case FramebufferTextureFormat::RGBA8:       return GL_RGBA8;
+                case FramebufferTextureFormat::RED_INTEGER: return GL_RED_INTEGER;
+            }
+
+            return 0;
+        }
+    }
+
+    OpenGLFramebuffer::OpenGLFramebuffer(const FramebufferSpecification& spec)
+        : m_specification(spec)
+    {
+        for (auto spec : m_specification.attachments.attachments)
+        {
+            if (!Utils::IsDepthFormat(spec.texture_format))
+                m_color_attachment_specifications.emplace_back(spec);
+            else
+                m_depth_attachment_specification = spec;
+        }
+
+        invalidate();
+    }
+
+    OpenGLFramebuffer::~OpenGLFramebuffer()
+    {
+        glDeleteFramebuffers(1, &m_renderer_id);
+        glDeleteTextures(static_cast<GLsizei>(m_color_attachments.size()), m_color_attachments.data());
+        glDeleteTextures(1, &m_depth_attachment);
+    }
+
+    auto OpenGLFramebuffer::invalidate() -> void
+    {
+        if (m_renderer_id)
+        {
+            glDeleteFramebuffers(1, &m_renderer_id);
+            glDeleteTextures(static_cast<GLsizei>(m_color_attachments.size()), m_color_attachments.data());
+            glDeleteTextures(1, &m_depth_attachment);
+
+            m_color_attachments.clear();
+            m_depth_attachment = 0;
+        }
+
+        glGenFramebuffers(1, &m_renderer_id); // glCreateFramebuffers is 4.5 DSA; unavailable on macOS 4.1
+        glBindFramebuffer(GL_FRAMEBUFFER, m_renderer_id);
+
+        bool multisample = m_specification.Samples > 1;
+
+        if (m_color_attachment_specifications.size())
+        {
+            m_color_attachments.resize(m_color_attachment_specifications.size());
+            Utils::CreateTextures(multisample, m_color_attachments.data(), static_cast<uint32_t>(m_color_attachments.size()));
+
+            for (size_t i = 0; i < m_color_attachments.size(); i++)
+            {
+                Utils::bind_texture(multisample, m_color_attachments[i]);
+                switch (m_color_attachment_specifications[i].texture_format)
+                {
+                    case FramebufferTextureFormat::RGBA8:
+                        Utils::AttachColorTexture(m_color_attachments[i], m_specification.Samples, GL_RGBA8, GL_RGBA, m_specification.Width, m_specification.Height, static_cast<int>(i));
+                        break;
+                    case FramebufferTextureFormat::RED_INTEGER:
+                        Utils::AttachColorTexture(m_color_attachments[i], m_specification.Samples, GL_R32I, GL_RED_INTEGER, m_specification.Width, m_specification.Height, static_cast<int>(i));
+                        break;
+                }
+            }
+        }
+
+        if (m_depth_attachment_specification.texture_format != FramebufferTextureFormat::None)
+        {
+            Utils::CreateTextures(multisample, &m_depth_attachment, 1);
+            Utils::bind_texture(multisample, m_depth_attachment);
+            switch (m_depth_attachment_specification.texture_format)
+            {
+                case FramebufferTextureFormat::DEPTH24STENCIL8:
+                    Utils::AttachDepthTexture(m_depth_attachment, m_specification.Samples, GL_DEPTH24_STENCIL8, GL_DEPTH_STENCIL_ATTACHMENT, m_specification.Width, m_specification.Height);
+                    break;
+            }
+        }
+
+        if (m_color_attachments.size() > 1)
+        {
+            GLenum buffers[4] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2, GL_COLOR_ATTACHMENT3 };
+            glDrawBuffers(static_cast<GLsizei>(m_color_attachments.size()), buffers);
+        }
+        else if (m_color_attachments.empty())
+            glDrawBuffer(GL_NONE);
+
+        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
+        {
+            GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
+            switch (status)
+            {
+                case GL_FRAMEBUFFER_UNDEFINED:
+                    DONUT_ERROR("Framebuffer is undefined");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT:
+                    DONUT_ERROR("Framebuffer has incomplete attachment");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT:
+                    DONUT_ERROR("Framebuffer is missing attachment");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER:
+                    DONUT_ERROR("Framebuffer has incomplete draw buffer");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER:
+                    DONUT_ERROR("Framebuffer has incomplete read buffer");
+                    break;
+                case GL_FRAMEBUFFER_UNSUPPORTED:
+                    DONUT_ERROR("Framebuffer format is unsupported");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE:
+                    DONUT_ERROR("Framebuffer has incomplete multisample");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_LAYER_TARGETS:
+                    DONUT_ERROR("Framebuffer has incomplete layer targets");
+                    break;
+                default:
+                    DONUT_ERROR("Framebuffer is incomplete (unknown error: {})", status);
+                    break;
+            }
+        }
+
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    }
+
+    auto OpenGLFramebuffer::bind() -> void
+    {
+        glBindFramebuffer(GL_FRAMEBUFFER, m_renderer_id);
+        glViewport(0, 0, m_specification.Width, m_specification.Height);
+    }
+
+    auto OpenGLFramebuffer::unbind() -> void
+    {
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    }
+
+    auto OpenGLFramebuffer::resize(uint32_t width, uint32_t height) -> void
+    {
+        m_specification.Width = width;
+        m_specification.Height = height;
+
+        invalidate();
+    }
+
+    auto OpenGLFramebuffer::read_pixel(uint32_t attachment_index, int x, int y) -> int
+    {
+        glReadBuffer(GL_COLOR_ATTACHMENT0 + attachment_index);
+        int pixel_data;
+        glReadPixels(x, y, 1, 1, GL_RED_INTEGER, GL_INT, &pixel_data);
+        return pixel_data;
+    }
+
+    auto OpenGLFramebuffer::clear_attachment(uint32_t attachment_index, int value) -> void
+    {
+        // glClearTexImage is 4.4 and unavailable on macOS. clear the integer
+        // attachment by binding this framebuffer and clearing its draw buffer.
+        glBindFramebuffer(GL_FRAMEBUFFER, m_renderer_id);
+        glClearBufferiv(GL_COLOR, static_cast<GLint>(attachment_index), &value);
+    }
+};
diff --git a/src/platform/opengl/opengl_framebuffer.h b/src/platform/opengl/opengl_framebuffer.h
new file mode 100644
index 0000000..456d924
--- /dev/null
+++ b/src/platform/opengl/opengl_framebuffer.h
@@ -0,0 +1,35 @@
+#pragma once
+
+#include "rendering/framebuffer.h"
+
+namespace Donut
+{
+    class OpenGLFramebuffer : public Framebuffer
+    {
+    public:
+        OpenGLFramebuffer(const FramebufferSpecification& spec);
+        virtual ~OpenGLFramebuffer();
+
+        auto invalidate() -> void;
+
+        virtual auto bind() -> void override;
+        virtual auto unbind() -> void override;
+
+        virtual auto resize(uint32_t width, uint32_t height) -> void override;
+        virtual auto read_pixel(uint32_t attachment_index, int x, int y) -> int override;
+
+        virtual auto clear_attachment(uint32_t attachment_index, int value) -> void override;
+        virtual auto get_color_attachment_renderer_id(uint32_t index = 0) const -> uint32_t override{ return m_color_attachments[index]; }
+
+        virtual auto get_specification() const -> const FramebufferSpecification& override{ return m_specification; }
+    private:
+        uint32_t m_renderer_id = 0;
+        FramebufferSpecification m_specification;
+
+        std::vector<FramebufferTextureSpecification> m_color_attachment_specifications;
+        FramebufferTextureSpecification m_depth_attachment_specification = FramebufferTextureFormat::None;
+
+        std::vector<uint32_t> m_color_attachments;
+        uint32_t m_depth_attachment = 0;
+    };
+};
diff --git a/src/platform/opengl/opengl_index_buffer.cpp b/src/platform/opengl/opengl_index_buffer.cpp
new file mode 100644
index 0000000..faa6b81
--- /dev/null
+++ b/src/platform/opengl/opengl_index_buffer.cpp
@@ -0,0 +1,28 @@
+#include "opengl_index_buffer.h"
+#include <glad/glad.h>
+
+namespace Donut
+{
+    OpenGLIndexBuffer::OpenGLIndexBuffer(const uint32_t* indices, uint32_t count)
+        : m_count(count)
+    {
+        glGenBuffers(1, &m_renderer_id); // glCreateBuffers is 4.5 DSA; unavailable on macOS 4.1
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_renderer_id);
+        glBufferData(GL_ELEMENT_ARRAY_BUFFER, count * sizeof(uint32_t), indices, GL_STATIC_DRAW);
+    }
+
+    OpenGLIndexBuffer::~OpenGLIndexBuffer() 
+    {
+        glDeleteBuffers(1, &m_renderer_id);
+    }
+
+    auto OpenGLIndexBuffer::bind() const -> void
+    {
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_renderer_id);
+    }
+
+    auto OpenGLIndexBuffer::unbind() const -> void
+    {
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+    }
+};
diff --git a/src/platform/opengl/opengl_index_buffer.h b/src/platform/opengl/opengl_index_buffer.h
new file mode 100644
index 0000000..397da43
--- /dev/null
+++ b/src/platform/opengl/opengl_index_buffer.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include "rendering/index_buffer.h"
+
+namespace Donut
+{
+    class OpenGLIndexBuffer
+        : public IndexBuffer 
+    {
+    public:
+        OpenGLIndexBuffer(const uint32_t* indices, uint32_t count);
+        virtual ~OpenGLIndexBuffer();
+
+        virtual auto bind() const -> void override;
+        virtual auto unbind() const -> void override;
+        virtual auto get_count() const -> uint32_t override{ return m_count; }
+
+    private:
+        uint32_t m_renderer_id;
+        uint32_t m_count;
+    };
+};
diff --git a/src/platform/opengl/opengl_renderer_api.cpp b/src/platform/opengl/opengl_renderer_api.cpp
new file mode 100644
index 0000000..39ed786
--- /dev/null
+++ b/src/platform/opengl/opengl_renderer_api.cpp
@@ -0,0 +1,118 @@
+#include "opengl_renderer_api.h"
+
+#include <glad/glad.h>
+#include <GLFW/glfw3.h>
+
+namespace Donut
+{
+    auto OpenGLRendererAPI::init() -> void
+    {
+        if (!glfwGetCurrentContext())
+        {
+            DONUT_ERROR("No OpenGL context is current! Cannot initialize GLAD.");
+            return;
+        }
+        
+        if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
+        {
+            DONUT_ERROR("Failed to initialize GLAD!");
+            return;
+        }
+        
+        glEnable(GL_BLEND);
+        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+        glEnable(GL_DEPTH_TEST);
+        glDepthFunc(GL_LESS);
+        
+        glEnable(GL_CULL_FACE);
+        glCullFace(GL_BACK);
+        glFrontFace(GL_CCW);
+    }
+
+    auto OpenGLRendererAPI::set_viewport(uint32_t x, uint32_t y, uint32_t width, uint32_t height) -> void
+    {
+        glViewport(x, y, width, height);
+    }
+
+    auto OpenGLRendererAPI::set_clear_color(const glm::vec4& color) -> void
+    {
+        glClearColor(color.r, color.g, color.b, color.a);
+    }
+
+    auto OpenGLRendererAPI::clear() -> void
+    {
+        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+    }
+
+    auto OpenGLRendererAPI::enable_depth_test() -> void
+    {
+        glEnable(GL_DEPTH_TEST);
+    }
+
+    auto OpenGLRendererAPI::disable_depth_test() -> void
+    {
+        glDisable(GL_DEPTH_TEST);
+    }
+
+    auto OpenGLRendererAPI::set_face_culling(bool enabled) -> void
+    {
+        if (enabled)
+        {
+            glEnable(GL_CULL_FACE);
+            glCullFace(GL_BACK);
+            glFrontFace(GL_CCW);
+        }
+        else
+            glDisable(GL_CULL_FACE);
+    }
+
+    auto OpenGLRendererAPI::enable_blending() -> void
+    {
+        glEnable(GL_BLEND);
+        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    }
+
+    auto OpenGLRendererAPI::disable_blending() -> void
+    {
+        glDisable(GL_BLEND);
+    }
+
+    auto OpenGLRendererAPI::draw_indexed(const Ref<VertexArray>& vertex_array, uint32_t index_count) -> void
+    {
+        uint32_t count = index_count ? index_count : vertex_array->get_index_buffer()->get_count();
+        glDrawElements(GL_TRIANGLES, count, GL_UNSIGNED_INT, nullptr);
+        glBindTexture(GL_TEXTURE_2D, 0);
+    }
+
+    auto OpenGLRendererAPI::draw_arrays(uint32_t vertex_count, uint32_t first) -> void
+    {
+        glDrawArrays(GL_TRIANGLES, first, vertex_count);
+    }
+
+    auto OpenGLRendererAPI::draw_lines(const Ref<VertexArray>& vertex_array, uint32_t index_count) -> void
+    {
+        uint32_t count = index_count ? index_count : vertex_array->get_index_buffer()->get_count();
+        glDrawElements(GL_LINES, count, GL_UNSIGNED_INT, nullptr);
+    }
+
+    auto OpenGLRendererAPI::bind_texture(uint32_t texture_id, uint32_t slot) -> void
+    {
+        glActiveTexture(GL_TEXTURE0 + slot);
+        glBindTexture(GL_TEXTURE_2D, texture_id);
+    }
+
+    auto OpenGLRendererAPI::bind_image_texture(uint32_t texture_id, uint32_t slot, bool read_only) -> void
+    {
+        // Image load/store is OpenGL 4.2; the pointer is null on macOS (4.1).
+        if (glBindImageTexture == nullptr)
+            return;
+        glBindImageTexture(slot, texture_id, 0, GL_FALSE, 0,
+                          read_only ? GL_READ_ONLY : GL_WRITE_ONLY, GL_RGBA8);
+    }
+
+    auto OpenGLRendererAPI::read_pixels(uint32_t x, uint32_t y, uint32_t width, uint32_t height, 
+                                       uint32_t format, uint32_t type, void* pixels) -> void
+    {
+        glReadPixels(x, y, width, height, format, type, pixels);
+    }
+};
diff --git a/src/platform/opengl/opengl_renderer_api.h b/src/platform/opengl/opengl_renderer_api.h
new file mode 100644
index 0000000..02f18ab
--- /dev/null
+++ b/src/platform/opengl/opengl_renderer_api.h
@@ -0,0 +1,44 @@
+#pragma once
+
+#include "core/memory.h"
+#include "core/log.h"
+
+#include "rendering/renderer.h"
+
+#include <glad/glad.h>
+
+namespace Donut
+{
+    class OpenGLRendererAPI 
+        : public RendererAPI
+    {
+    public:
+        virtual auto init() -> void override;
+        virtual void set_viewport(uint32_t x,     uint32_t y, 
+                                 uint32_t width, uint32_t height) override;
+        virtual auto set_clear_color(const glm::vec4& color) -> void override;
+        virtual auto clear() -> void override;
+        virtual auto enable_depth_test() -> void override;
+        virtual auto disable_depth_test() -> void override;
+        virtual auto set_face_culling(bool enabled) -> void override;
+        virtual auto enable_blending() -> void override;
+        virtual auto disable_blending() -> void override;
+
+        virtual void draw_indexed(const Ref<VertexArray>& vertex_array, 
+                                 uint32_t index_count = 0)         override;
+        
+        virtual void draw_arrays(uint32_t vertex_count, 
+                                uint32_t first = 0)               override;
+        virtual void draw_lines(const Ref<VertexArray>& vertex_array, 
+                               uint32_t index_count = 0)           override;
+        virtual void bind_texture(uint32_t texture_id, 
+                                 uint32_t slot = 0)               override;
+        virtual void bind_image_texture(uint32_t texture_id, 
+                                      uint32_t slot = 0, 
+                                      bool read_only = false)      override;
+        virtual void read_pixels(uint32_t x, uint32_t y, 
+                                uint32_t width,  uint32_t height, 
+                                uint32_t format, uint32_t type, 
+                                void* pixels)                     override;
+    };
+};
diff --git a/src/platform/opengl/opengl_shader.cpp b/src/platform/opengl/opengl_shader.cpp
new file mode 100644
index 0000000..d15d7e0
--- /dev/null
+++ b/src/platform/opengl/opengl_shader.cpp
@@ -0,0 +1,302 @@
+#include "opengl_shader.h"
+
+#include <glad/glad.h>
+#include <glm/gtc/type_ptr.hpp>
+
+#include <fstream>
+#include <iostream>
+
+namespace Donut
+{
+    static uint32_t ShaderTypeFromString(const std::string& type)
+    {
+        if (type == "vertex")
+            return GL_VERTEX_SHADER;
+        if (type == "fragment" || type == "pixel")
+            return GL_FRAGMENT_SHADER;
+        if (type == "compute")
+            return GL_COMPUTE_SHADER;
+        return 0;
+    }
+
+    // Shaders are authored in Slang and compiled to assets/shaders/generated/
+    // <name>.glsl by Tools/compile-shaders.sh. Given a legacy ".../<name>.glsl"
+    // path, prefer that generated file when present; otherwise fall back to the
+    // hand-written GLSL (e.g. shaders not yet ported to Slang).
+    static std::string ResolveShaderPath(const std::string& filepath)
+    {
+        size_t slash = filepath.find_last_of("/\\");
+        std::string dir  = (slash == std::string::npos) ? std::string() : filepath.substr(0, slash + 1);
+        std::string file = (slash == std::string::npos) ? filepath : filepath.substr(slash + 1);
+        size_t dot = file.rfind('.');
+        std::string base = (dot == std::string::npos) ? file : file.substr(0, dot);
+
+        std::string generated = dir + "generated/" + base + ".glsl";
+        std::ifstream test(generated);
+        if (test.good())
+            return generated;
+        return filepath;
+    }
+
+    OpenGLShader::OpenGLShader(const std::string& filepath)
+    {
+        std::string resolved = ResolveShaderPath(filepath);
+        m_is_slang = (resolved != filepath);
+        std::string source = read_file(resolved);
+        auto shader_sources = pre_process(source);
+        compile(shader_sources);
+
+        auto last_slash = filepath.find_last_of("/\\");
+        last_slash = last_slash == std::string::npos ? 0 : last_slash + 1;
+        auto last_dot = filepath.rfind('.');
+        auto count = last_dot == std::string::npos ? filepath.size() - last_slash : last_dot - last_slash;
+        m_name = filepath.substr(last_slash, count);
+    }
+
+    OpenGLShader::OpenGLShader(const std::string& name, const std::string& vertex_src, const std::string& fragment_src)
+        : m_name(name)
+    {
+        std::unordered_map<uint32_t, std::string> sources;
+        sources[GL_VERTEX_SHADER] = vertex_src;
+        sources[GL_FRAGMENT_SHADER] = fragment_src;
+        compile(sources);
+    }
+
+    OpenGLShader::OpenGLShader(const std::string& name, const std::string& compute_src)
+        : m_name(name)
+    {
+        std::unordered_map<uint32_t, std::string> sources;
+        sources[GL_COMPUTE_SHADER] = compute_src;
+        compile(sources);
+    }
+
+    OpenGLShader::~OpenGLShader()
+    {
+        glDeleteProgram(m_renderer_id);
+    }
+
+    auto OpenGLShader::read_file(const std::string& filepath) -> std::string
+    {
+        std::string result;
+        std::ifstream in(filepath, std::ios::in |
+                                   std::ios::binary);
+
+        if (in)
+        {
+            in.seekg(0, std::ios::end);
+            size_t size = in.tellg();
+            if (size != -1)
+            {
+                result.resize(size);
+                in.seekg(0, std::ios::beg);
+                in.read(&result[0], size);
+            }
+        }
+        return result;
+    }
+
+    auto OpenGLShader::pre_process(const std::string& source) -> std::unordered_map<uint32_t, std::string>
+    {
+        std::unordered_map<uint32_t, std::string> shader_sources;
+
+        const char* type_token = "#type";
+        size_t type_token_length = strlen(type_token);
+        size_t pos = source.find(type_token, 0);
+
+        while (pos != std::string::npos)
+        {
+            size_t eol = source.find_first_of("\r\n", pos);
+            size_t begin = pos + type_token_length + 1;
+            std::string type = source.substr(begin, eol - begin);
+
+            size_t next_line_pos = source.find_first_not_of("\r\n", eol);
+            pos = source.find(type_token, next_line_pos);
+            shader_sources[ShaderTypeFromString(type)] = (pos == std::string::npos) ? source.substr(next_line_pos) :
+            source.substr(next_line_pos, pos - next_line_pos);
+        }
+
+        return shader_sources;
+    }
+
+    auto OpenGLShader::compile(const std::unordered_map<uint32_t, std::string>& shader_sources) -> void
+    {
+        uint32_t program = glCreateProgram();
+        std::vector<uint32_t> glShaderIDs(shader_sources.size());
+        for (auto& kv : shader_sources)
+        {
+            uint32_t type = kv.first;
+            const std::string& source = kv.second;
+
+            uint32_t shader = glCreateShader(type);
+            const char* source_c_str = source.c_str();
+            glShaderSource(shader, 1, &source_c_str, 0);
+            glCompileShader(shader);
+
+            int is_compiled = 0;
+            glGetShaderiv(shader, GL_COMPILE_STATUS, &is_compiled);
+            if (is_compiled == GL_FALSE)
+            {
+                int max_length = 0;
+                glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &max_length);
+                std::vector<char> info_log(max_length);
+                glGetShaderInfoLog(shader, max_length, &max_length, &info_log[0]);
+                glDeleteShader(shader);
+                for (auto id : glShaderIDs)
+                    glDeleteShader(id);
+                glDeleteProgram(program);
+                m_renderer_id = 0;
+                // info_log.data() is null when the driver returns an empty log
+                // (e.g. macOS rejecting a compute shader); streaming a null
+                // char* into std::cout calls strlen(NULL) and crashes.
+                const char* log = info_log.empty() ? "" : info_log.data();
+                std::cout << "Shader compilation failure!" << std::endl << log << std::endl;
+                return;
+            }
+            glAttachShader(program, shader);
+            glShaderIDs.push_back(shader);
+        }
+
+        m_renderer_id = program;
+        glLinkProgram(m_renderer_id);
+
+        int is_linked = 0;
+        glGetProgramiv(m_renderer_id, GL_LINK_STATUS, (int*)&is_linked);
+        if (is_linked == GL_FALSE)
+        {
+            int max_length = 0;
+            glGetProgramiv(m_renderer_id, GL_INFO_LOG_LENGTH, &max_length);
+            std::vector<char> info_log(max_length);
+            glGetProgramInfoLog(m_renderer_id, max_length, &max_length, &info_log[0]);
+            glDeleteProgram(m_renderer_id);
+            for (auto id : glShaderIDs)
+                glDeleteShader(id);
+            m_renderer_id = 0;
+            const char* log = info_log.empty() ? "" : info_log.data();
+            std::cout << "Shader link failure!" << std::endl << log << std::endl;
+            return;
+        }
+
+        for (auto id : glShaderIDs)
+        {
+            glDetachShader(m_renderer_id, id);
+            glDeleteShader(id);
+        }
+    }
+
+    auto OpenGLShader::bind() const -> void
+    {
+        glUseProgram(m_renderer_id);
+    }
+
+    auto OpenGLShader::unbind() const -> void
+    {
+        glUseProgram(0);
+    }
+
+    auto OpenGLShader::set_int(const std::string& name, int value) -> void
+    {
+        upload_uniform_int(name, value);
+    }
+
+    auto OpenGLShader::set_int_array(const std::string& name, int* values, uint32_t count) -> void
+    {
+        upload_uniform_int_array(name, values, count);
+    }
+
+    auto OpenGLShader::set_float(const std::string& name, float value) -> void
+    {
+        upload_uniform_float(name, value);
+    }
+
+    auto OpenGLShader::set_float2(const std::string& name, const glm::vec2& value) -> void
+    {
+        upload_uniform_float2(name, value);
+    }
+
+    auto OpenGLShader::set_float3(const std::string& name, const glm::vec3& value) -> void
+    {
+        upload_uniform_float3(name, value);
+    }
+
+    auto OpenGLShader::set_float4(const std::string& name, const glm::vec4& value) -> void
+    {
+        upload_uniform_float4(name, value);
+    }
+
+    auto OpenGLShader::set_mat4(const std::string& name, const glm::mat4& value) -> void
+    {
+        upload_uniform_mat4(name, value);
+    }
+
+    auto OpenGLShader::upload_uniform_int(const std::string& name, int value) -> void
+    {
+        int location = glGetUniformLocation(m_renderer_id, name.c_str());
+        glUniform1i(location, value);
+    }
+
+    auto OpenGLShader::upload_uniform_int_array(const std::string& name, int* values, uint32_t count) -> void
+    {
+        int location = glGetUniformLocation(m_renderer_id, name.c_str());
+        glUniform1iv(location, count, values);
+    }
+
+    auto OpenGLShader::upload_uniform_float(const std::string& name, float value) -> void
+    {
+        int location = glGetUniformLocation(m_renderer_id, name.c_str());
+        glUniform1f(location, value);
+    }
+
+    auto OpenGLShader::upload_uniform_float2(const std::string& name, const glm::vec2& value) -> void
+    {
+        int location = glGetUniformLocation(m_renderer_id, name.c_str());
+        glUniform2f(location, value.x, value.y);
+    }
+
+    auto OpenGLShader::upload_uniform_float3(const std::string& name, const glm::vec3& value) -> void
+    {
+        int location = glGetUniformLocation(m_renderer_id, name.c_str());
+        glUniform3f(location, value.x, value.y, value.z);
+    }
+
+    auto OpenGLShader::upload_uniform_float4(const std::string& name, const glm::vec4& value) -> void
+    {
+        int location = glGetUniformLocation(m_renderer_id, name.c_str());
+        glUniform4f(location, value.x, value.y, value.z, value.w);
+    }
+
+    auto OpenGLShader::upload_uniform_mat3(const std::string& name, const glm::mat3& matrix) -> void
+    {
+        int location = glGetUniformLocation(m_renderer_id, name.c_str());
+        glUniformMatrix3fv(location, 1, m_is_slang ? GL_TRUE : GL_FALSE, glm::value_ptr(matrix));
+    }
+
+    auto OpenGLShader::upload_uniform_mat4(const std::string& name, const glm::mat4& matrix) -> void
+    {
+        int location = glGetUniformLocation(m_renderer_id, name.c_str());
+        glUniformMatrix4fv(location, 1, m_is_slang ? GL_TRUE : GL_FALSE, glm::value_ptr(matrix));
+    }
+
+    auto OpenGLShader::dispatch(uint32_t x, uint32_t y, uint32_t z) -> void
+    {
+        // Compute shaders require OpenGL 4.3+. On drivers that cap out earlier
+        // (e.g. macOS, which is frozen at 4.1) glDispatchCompute is never
+        // loaded and the pointer is null. Guard so we no-op instead of crash.
+        if (m_renderer_id == 0 || glDispatchCompute == nullptr)
+            return;
+        glDispatchCompute(x, y, z);
+    }
+
+    auto OpenGLShader::dispatch_indirect(uint32_t offset) -> void
+    {
+        if (m_renderer_id == 0 || glDispatchComputeIndirect == nullptr)
+            return;
+        glDispatchComputeIndirect(offset);
+    }
+
+    auto OpenGLShader::memory_barrier(uint32_t barriers) -> void
+    {
+        if (glMemoryBarrier == nullptr)
+            return;
+        glMemoryBarrier(barriers);
+    }
+};
diff --git a/src/platform/opengl/opengl_shader.h b/src/platform/opengl/opengl_shader.h
new file mode 100644
index 0000000..289bfac
--- /dev/null
+++ b/src/platform/opengl/opengl_shader.h
@@ -0,0 +1,58 @@
+#pragma once
+
+#include "rendering/shader.h"
+
+#include <unordered_map>
+#include <glm/glm.hpp>
+
+namespace Donut 
+{
+    class OpenGLShader 
+        : public Shader 
+    {
+    public:
+        OpenGLShader(const std::string& filepath);
+        OpenGLShader(const std::string& name, const std::string& vertex_src, const std::string& fragment_src);
+        OpenGLShader(const std::string& name, const std::string& compute_src);
+        virtual ~OpenGLShader();
+
+        virtual auto bind() const -> void override;
+        virtual auto unbind() const -> void override;
+
+        virtual auto set_int(     const std::string& name, int value) -> void override;
+        virtual auto set_int_array(const std::string& name, int* values, uint32_t count) -> void override;
+        virtual auto set_float(   const std::string& name, float value) -> void override;
+        virtual auto set_float2(  const std::string& name, const glm::vec2& value) -> void override;
+        virtual auto set_float3(  const std::string& name, const glm::vec3& value) -> void override;
+        virtual auto set_float4(  const std::string& name, const glm::vec4& value) -> void override;
+        virtual auto set_mat4(    const std::string& name, const glm::mat4& value) -> void override;
+
+        virtual auto dispatch(uint32_t x, uint32_t y = 1, uint32_t z = 1) -> void override;
+        virtual auto dispatch_indirect(uint32_t offset = 0) -> void override;
+        virtual auto memory_barrier(uint32_t barriers) -> void override;
+
+        virtual auto get_name() const -> const std::string& override{ return m_name; }
+        virtual auto get_renderer_id() const -> uint32_t override{ return m_renderer_id; }
+
+        auto upload_uniform_int(     const std::string& name, int value) -> void;
+        auto upload_uniform_int_array(const std::string& name, int* values, uint32_t count) -> void;
+        auto upload_uniform_float(   const std::string& name, float value) -> void;
+        auto upload_uniform_float2(  const std::string& name, const glm::vec2& value) -> void;
+        auto upload_uniform_float3(  const std::string& name, const glm::vec3& value) -> void;
+        auto upload_uniform_float4(  const std::string& name, const glm::vec4& value) -> void;
+        auto upload_uniform_mat3(    const std::string& name, const glm::mat3& matrix) -> void;
+        auto upload_uniform_mat4(    const std::string& name, const glm::mat4& matrix) -> void;
+
+    private:
+        auto read_file(const std::string& filepath) -> std::string;
+        auto pre_process(const std::string& source) -> std::unordered_map<uint32_t, std::string>;
+        auto compile(const std::unordered_map<uint32_t, std::string>& shader_sources) -> void;
+    private:
+        uint32_t    m_renderer_id = 0;
+        std::string m_name;
+        // True when loaded from a Slang-compiled GLSL. Slang expects row-major
+        // matrix data, so matrix uniforms are transposed on upload (glm is
+        // column-major) to keep all matrix math correct.
+        bool        m_is_slang = false;
+    };
+};
diff --git a/src/platform/opengl/opengl_texture.cpp b/src/platform/opengl/opengl_texture.cpp
new file mode 100644
index 0000000..6bcb9cd
--- /dev/null
+++ b/src/platform/opengl/opengl_texture.cpp
@@ -0,0 +1,272 @@
+#include "opengl_texture.h"
+
+#include "rendering/shader.h"
+
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+#include <glm/glm.hpp>
+#include <glm/gtc/matrix_transform.hpp>
+#include <glm/gtc/type_ptr.hpp>
+
+// NOTE: This file targets OpenGL 4.1 (the maximum macOS exposes). It uses the
+// classic bind-based texture API rather than 4.5 Direct State Access
+// (glCreateTextures / glTextureStorage2D / glTextureParameteri / glBindTextureUnit),
+// none of which exist on macOS.
+
+namespace Donut
+{
+    OpenGLTexture2D::OpenGLTexture2D(uint32_t width, uint32_t height)
+        : m_width(width), m_height(height)
+    {
+        m_internal_format = GL_RGBA8;
+        m_data_format     = GL_RGBA;
+
+        glGenTextures(1, &m_renderer_id);
+        glBindTexture(GL_TEXTURE_2D, m_renderer_id);
+        glTexImage2D(GL_TEXTURE_2D, 0, m_internal_format, m_width, m_height, 0, m_data_format, GL_UNSIGNED_BYTE, nullptr);
+
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
+    }
+
+    OpenGLTexture2D::OpenGLTexture2D(const std::string& path)
+        : m_path(path)
+    {
+        m_width          = 1;
+        m_height         = 1;
+        m_internal_format = GL_RGBA8;
+        m_data_format     = GL_RGBA;
+
+        glGenTextures(1, &m_renderer_id);
+        glBindTexture(GL_TEXTURE_2D, m_renderer_id);
+        glTexImage2D(GL_TEXTURE_2D, 0, m_internal_format, m_width, m_height, 0, m_data_format, GL_UNSIGNED_BYTE, nullptr);
+
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
+
+        uint32_t white_pixel = 0xFFFFFFFF;
+        glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, m_width, m_height, m_data_format, GL_UNSIGNED_BYTE, &white_pixel);
+
+        DONUT_INFO("Created default texture (stb_image not available for loading: ", path, ")");
+    }
+
+    OpenGLTexture2D::~OpenGLTexture2D()
+    {
+        glDeleteTextures(1, &m_renderer_id);
+    }
+
+    auto OpenGLTexture2D::set_data(void* data, uint32_t size) -> void
+    {
+        uint32_t bpp = m_data_format == GL_RGBA ? 4 : 3;
+        if (size != m_width * m_height * bpp)
+        {
+            DONUT_ERROR("Data must be entire texture!");
+            return;
+        }
+
+        glBindTexture(GL_TEXTURE_2D, m_renderer_id);
+        glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, m_width, m_height, m_data_format, GL_UNSIGNED_BYTE, data);
+    }
+
+    auto OpenGLTexture2D::bind(uint32_t slot) const -> void
+    {
+        glActiveTexture(GL_TEXTURE0 + slot);
+        glBindTexture(GL_TEXTURE_2D, m_renderer_id);
+    }
+
+    auto OpenGLTexture2D::bind_as_image(uint32_t slot, bool read_only) const -> void
+    {
+        // Image load/store is OpenGL 4.2 and unavailable on macOS. Guard the
+        // function pointer so this degrades to a no-op instead of crashing.
+        if (glBindImageTexture == nullptr)
+            return;
+        GLenum access = read_only ? GL_READ_ONLY : GL_WRITE_ONLY;
+        glBindImageTexture(slot, m_renderer_id, 0, GL_FALSE, 0, access, m_internal_format);
+    }
+
+    OpenGLCubemapTexture::OpenGLCubemapTexture(uint32_t width, uint32_t height)
+        : m_width(width), m_height(height)
+    {
+        m_internal_format = GL_RGBA16F;
+        m_data_format     = GL_RGBA;
+
+        glGenTextures(1, &m_renderer_id);
+        glBindTexture(GL_TEXTURE_CUBE_MAP, m_renderer_id);
+        for (uint32_t i = 0; i < 6; ++i)
+            glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, m_internal_format, m_width, m_height, 0, m_data_format, GL_FLOAT, nullptr);
+
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
+    }
+
+    OpenGLCubemapTexture::OpenGLCubemapTexture(const std::string& path)
+        : m_path(path)
+    {
+        m_width          = 1024;
+        m_height         = 1024;
+        m_internal_format = GL_RGBA16F;
+        m_data_format     = GL_RGBA;
+
+        glGenTextures(1, &m_renderer_id);
+        glBindTexture(GL_TEXTURE_CUBE_MAP, m_renderer_id);
+        for (uint32_t i = 0; i < 6; ++i)
+            glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, m_internal_format, m_width, m_height, 0, m_data_format, GL_FLOAT, nullptr);
+
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
+
+        LoadHDRI(path);
+    }
+
+    OpenGLCubemapTexture::~OpenGLCubemapTexture()
+    {
+        glDeleteTextures(1, &m_renderer_id);
+    }
+
+    auto OpenGLCubemapTexture::LoadHDRI(const std::string& path) -> void
+    {
+        stbi_set_flip_vertically_on_load(true);
+        int width, height, channels;
+        float* hdr_data = stbi_loadf(path.c_str(), &width, &height, &channels, 3);
+
+        if (!hdr_data)
+        {
+            DONUT_ERROR("Failed to load HDRI: {}", path);
+            float default_sky[6 * 4] =
+            {
+                0.5f, 0.7f, 1.0f, 1.0f,  // Right
+                0.5f, 0.7f, 1.0f, 1.0f,  // Left
+                0.5f, 0.7f, 1.0f, 1.0f,  // Top
+                0.5f, 0.7f, 1.0f, 1.0f,  // Bottom
+                0.5f, 0.7f, 1.0f, 1.0f,  // Front
+                0.5f, 0.7f, 1.0f, 1.0f   // Back
+            };
+
+            glBindTexture(GL_TEXTURE_CUBE_MAP, m_renderer_id);
+            for (int i = 0; i < 6; ++i)
+                glTexSubImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, 0, 0, 1, 1, GL_RGBA, GL_FLOAT, &default_sky[i * 4]);
+            return;
+        }
+
+        convert_equirectangular_to_cubemap(hdr_data, width, height);
+        stbi_image_free(hdr_data);
+
+        DONUT_INFO("Successfully loaded HDRI: {} ({}x{})", path, width, height);
+    }
+
+    auto OpenGLCubemapTexture::convert_equirectangular_to_cubemap(float* hdr_data, int width, int height) -> void
+    {
+        uint32_t capture_fbo, capture_rbo;
+        glGenFramebuffers(1, &capture_fbo);
+        glGenRenderbuffers(1, &capture_rbo);
+
+        glBindFramebuffer(GL_FRAMEBUFFER, capture_fbo);
+        glBindRenderbuffer(GL_RENDERBUFFER, capture_rbo);
+        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, m_width, m_height);
+        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, capture_rbo);
+
+        uint32_t hdr_texture;
+        glGenTextures(1, &hdr_texture);
+        glBindTexture(GL_TEXTURE_2D, hdr_texture);
+        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB16F, width, height, 0, GL_RGB, GL_FLOAT, hdr_data);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+
+        auto equirect_shader = Shader::create("assets/shaders/EquirectToCubemap.glsl");
+        if (!equirect_shader)
+        {
+            DONUT_ERROR("Failed to create equirectangular to cubemap shader");
+            return;
+        }
+
+        uint32_t shader_program = equirect_shader->get_renderer_id();
+
+        float vertices[] =
+        {
+            -1.0f,  1.0f, -1.0f, -1.0f, -1.0f, -1.0f,  1.0f, -1.0f, -1.0f,  1.0f, -1.0f, -1.0f,  1.0f,  1.0f, -1.0f, -1.0f,  1.0f, -1.0f,
+            -1.0f, -1.0f,  1.0f, -1.0f, -1.0f, -1.0f, -1.0f,  1.0f, -1.0f, -1.0f,  1.0f, -1.0f, -1.0f,  1.0f,  1.0f, -1.0f, -1.0f,  1.0f,
+             1.0f, -1.0f, -1.0f,  1.0f, -1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f, -1.0f,  1.0f, -1.0f, -1.0f,
+            -1.0f, -1.0f,  1.0f, -1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f, -1.0f,  1.0f, -1.0f, -1.0f,  1.0f,
+            -1.0f,  1.0f, -1.0f,  1.0f,  1.0f, -1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f,  1.0f, -1.0f,  1.0f,  1.0f, -1.0f,  1.0f, -1.0f,
+            -1.0f, -1.0f, -1.0f, -1.0f, -1.0f,  1.0f,  1.0f, -1.0f, -1.0f,  1.0f, -1.0f, -1.0f,  1.0f, -1.0f,  1.0f, -1.0f, -1.0f,  1.0f
+        };
+
+        uint32_t cube_vao, cube_vbo;
+        glGenVertexArrays(1, &cube_vao);
+        glGenBuffers(1, &cube_vbo);
+        glBindVertexArray(cube_vao);
+        glBindBuffer(GL_ARRAY_BUFFER, cube_vbo);
+        glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+        glEnableVertexAttribArray(0);
+        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
+
+        glm::mat4 capture_projection = glm::perspective(glm::radians(90.0f), 1.0f, 0.1f, 10.0f);
+        glm::mat4 capture_views[] =
+        {
+            glm::lookAt(glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3( 1.0f,  0.0f,  0.0f), glm::vec3(0.0f, -1.0f,  0.0f)),
+            glm::lookAt(glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(-1.0f,  0.0f,  0.0f), glm::vec3(0.0f, -1.0f,  0.0f)),
+            glm::lookAt(glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3( 0.0f,  1.0f,  0.0f), glm::vec3(0.0f,  0.0f,  1.0f)),
+            glm::lookAt(glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3( 0.0f, -1.0f,  0.0f), glm::vec3(0.0f,  0.0f, -1.0f)),
+            glm::lookAt(glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3( 0.0f,  0.0f,  1.0f), glm::vec3(0.0f, -1.0f,  0.0f)),
+            glm::lookAt(glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3( 0.0f,  0.0f, -1.0f), glm::vec3(0.0f, -1.0f,  0.0f))
+        };
+
+        glUseProgram(shader_program);
+        glUniform1i(glGetUniformLocation(shader_program, "u_EquirectangularMap"), 0);
+        // EquirectToCubemap is authored in Slang (row-major); transpose glm's
+        // column-major matrices on upload (GL_TRUE) to match.
+        glUniformMatrix4fv(glGetUniformLocation(shader_program, "u_Projection"), 1, GL_TRUE, &capture_projection[0][0]);
+        glActiveTexture(GL_TEXTURE0);
+        glBindTexture(GL_TEXTURE_2D, hdr_texture);
+
+        glViewport(0, 0, m_width, m_height);
+        glBindFramebuffer(GL_FRAMEBUFFER, capture_fbo);
+        for (unsigned int i = 0; i < 6; ++i)
+        {
+            glUniformMatrix4fv(glGetUniformLocation(shader_program, "u_View"), 1, GL_TRUE, &capture_views[i][0][0]);
+            glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, m_renderer_id, 0);
+            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+            glBindVertexArray(cube_vao);
+            glDrawArrays(GL_TRIANGLES, 0, 36);
+        }
+        glBindVertexArray(0);
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
+        glDeleteVertexArrays(1, &cube_vao);
+        glDeleteBuffers(1, &cube_vbo);
+        glDeleteTextures(1, &hdr_texture);
+        glDeleteFramebuffers(1, &capture_fbo);
+        glDeleteRenderbuffers(1, &capture_rbo);
+    }
+
+    auto OpenGLCubemapTexture::set_data(void* data, uint32_t size) -> void
+    {
+        DONUT_WARN("set_data not implemented for cubemaps");
+    }
+
+    auto OpenGLCubemapTexture::bind(uint32_t slot) const -> void
+    {
+        glActiveTexture(GL_TEXTURE0 + slot);
+        glBindTexture(GL_TEXTURE_CUBE_MAP, m_renderer_id);
+    }
+
+    auto OpenGLCubemapTexture::bind_as_image(uint32_t slot, bool read_only) const -> void
+    {
+        if (glBindImageTexture == nullptr)
+            return;
+        GLenum access = read_only ? GL_READ_ONLY : GL_WRITE_ONLY;
+        glBindImageTexture(slot, m_renderer_id, 0, GL_TRUE, 0, access, m_internal_format);
+    }
+};
diff --git a/src/platform/opengl/opengl_texture.h b/src/platform/opengl/opengl_texture.h
new file mode 100644
index 0000000..7aa87ea
--- /dev/null
+++ b/src/platform/opengl/opengl_texture.h
@@ -0,0 +1,68 @@
+#pragma once
+
+#include "rendering/texture.h"
+#include "core/log.h"
+
+#include <glad/glad.h>
+
+namespace Donut
+{
+    class OpenGLTexture2D 
+        : public Texture2D
+    {
+    public:
+        OpenGLTexture2D(uint32_t width, uint32_t height);
+        OpenGLTexture2D(const std::string& path);
+        virtual ~OpenGLTexture2D();
+
+        virtual auto get_width() const -> uint32_t override{ return m_width; }
+        virtual auto get_height() const -> uint32_t override{ return m_height; }
+        virtual auto get_renderer_id() const -> uint32_t override{ return m_renderer_id; }
+
+        virtual auto set_data(void* data, uint32_t size) -> void override;
+        virtual auto bind(uint32_t slot = 0) const -> void override;
+        virtual auto bind_as_image(uint32_t slot = 0, bool read_only = false) const -> void override;
+
+        virtual bool operator==(const Texture& other) const override
+        {
+            return m_renderer_id == other.get_renderer_id();
+        }
+
+    private:
+        std::string m_path;
+        uint32_t    m_width, m_height;
+        uint32_t    m_renderer_id;
+        GLenum      m_internal_format, m_data_format;
+    };
+
+    class OpenGLCubemapTexture 
+        : public CubemapTexture
+    {
+    public:
+        OpenGLCubemapTexture(uint32_t width, uint32_t height);
+        OpenGLCubemapTexture(const std::string& path);
+        virtual ~OpenGLCubemapTexture();
+
+        virtual auto get_width() const -> uint32_t override{ return m_width; }
+        virtual auto get_height() const -> uint32_t override{ return m_height; }
+        virtual auto get_renderer_id() const -> uint32_t override{ return m_renderer_id; }
+
+        virtual auto set_data(void* data, uint32_t size) -> void override;
+        virtual auto bind(uint32_t slot = 0) const -> void override;
+        virtual auto bind_as_image(uint32_t slot = 0, bool read_only = false) const -> void override;
+
+        virtual bool operator==(const Texture& other) const override
+        {
+            return m_renderer_id == other.get_renderer_id();
+        }
+
+    private:
+        void LoadHDRI(const std::string& path);
+        auto convert_equirectangular_to_cubemap(float* hdr_data, int width, int height) -> void;
+
+        std::string m_path;
+        uint32_t    m_width, m_height;
+        uint32_t    m_renderer_id;
+        GLenum      m_internal_format, m_data_format;
+    };
+}
diff --git a/src/platform/opengl/opengl_uniform_buffer.cpp b/src/platform/opengl/opengl_uniform_buffer.cpp
new file mode 100644
index 0000000..9b3b6d2
--- /dev/null
+++ b/src/platform/opengl/opengl_uniform_buffer.cpp
@@ -0,0 +1,29 @@
+#include "opengl_uniform_buffer.h"
+
+namespace Donut
+{
+    OpenGLUniformBuffer::OpenGLUniformBuffer(uint32_t size, uint32_t binding)
+        : m_size(size), m_binding(binding)
+    {
+        glGenBuffers(1, &m_renderer_id);
+        glBindBuffer(GL_UNIFORM_BUFFER, m_renderer_id);
+        glBufferData(GL_UNIFORM_BUFFER, size, nullptr, GL_DYNAMIC_DRAW);
+        glBindBufferBase(GL_UNIFORM_BUFFER, binding, m_renderer_id);
+    }
+
+    OpenGLUniformBuffer::~OpenGLUniformBuffer()
+    {
+        glDeleteBuffers(1, &m_renderer_id);
+    }
+
+    auto OpenGLUniformBuffer::set_data(const void* data, uint32_t size, uint32_t offset) -> void
+    {
+        glBindBuffer(GL_UNIFORM_BUFFER, m_renderer_id);
+        glBufferSubData(GL_UNIFORM_BUFFER, offset, size, data);
+    }
+
+    auto OpenGLUniformBuffer::bind(uint32_t binding) -> void
+    {
+        glBindBufferBase(GL_UNIFORM_BUFFER, binding, m_renderer_id);
+    }
+};
diff --git a/src/platform/opengl/opengl_uniform_buffer.h b/src/platform/opengl/opengl_uniform_buffer.h
new file mode 100644
index 0000000..db137a0
--- /dev/null
+++ b/src/platform/opengl/opengl_uniform_buffer.h
@@ -0,0 +1,21 @@
+#pragma once
+
+#include "rendering/uniform_buffer.h"
+#include <glad/glad.h>
+
+namespace Donut
+{
+    class OpenGLUniformBuffer : public UniformBuffer
+    {
+    public:
+        OpenGLUniformBuffer(uint32_t size, uint32_t binding);
+        virtual ~OpenGLUniformBuffer();
+
+        virtual auto set_data(const void* data, uint32_t size, uint32_t offset = 0) -> void override;
+        virtual auto bind(uint32_t binding) -> void override;
+    private:
+        uint32_t m_renderer_id = 0;
+        uint32_t m_size       = 0;
+        uint32_t m_binding    = 0;
+    };
+};
diff --git a/src/platform/opengl/opengl_vertex_array.cpp b/src/platform/opengl/opengl_vertex_array.cpp
new file mode 100644
index 0000000..01e6f56
--- /dev/null
+++ b/src/platform/opengl/opengl_vertex_array.cpp
@@ -0,0 +1,58 @@
+#include <glad/glad.h>
+
+#include "opengl_vertex_array.h"
+#include "rendering/vertex_buffer.h"
+#include "rendering/index_buffer.h"
+
+namespace Donut
+{
+    OpenGLVertexArray::OpenGLVertexArray()
+    {
+        // glCreateVertexArrays is 4.5 DSA; macOS caps at 4.1. glGenVertexArrays
+        // reserves the name and the VAO is created on first bind (done below).
+        glGenVertexArrays(1, &m_renderer_id);
+    }
+
+    OpenGLVertexArray::~OpenGLVertexArray() 
+    {
+        glDeleteVertexArrays(1, &m_renderer_id);
+    }
+
+    auto OpenGLVertexArray::bind() const -> void
+    {
+        glBindVertexArray(m_renderer_id);
+    }
+
+    auto OpenGLVertexArray::unbind() const -> void
+    {
+        glBindVertexArray(0);
+    }
+
+    auto OpenGLVertexArray::add_vertex_buffer(const Ref<VertexBuffer>& vertex_buffer) -> void
+    {
+        glBindVertexArray(m_renderer_id);
+        vertex_buffer->bind();
+
+        const auto& layout = vertex_buffer->get_layout();
+        for (const auto& element : layout.get_elements()) 
+        {
+            glEnableVertexAttribArray(m_vertex_buffer_index);
+            glVertexAttribPointer(m_vertex_buffer_index,
+                element.count,
+                element.type,
+                element.normalized ? GL_TRUE : GL_FALSE,
+                layout.get_stride(),
+                reinterpret_cast<const   void*>(static_cast<uintptr_t>(element.offset)));
+            m_vertex_buffer_index++;
+        }
+
+        m_vertex_buffers.push_back(vertex_buffer);
+    }
+
+    auto OpenGLVertexArray::set_index_buffer(const Ref<IndexBuffer>& index_buffer) -> void
+    {
+        glBindVertexArray(m_renderer_id);
+        index_buffer->bind();
+        m_index_buffer = index_buffer;
+    }
+};
diff --git a/src/platform/opengl/opengl_vertex_array.h b/src/platform/opengl/opengl_vertex_array.h
new file mode 100644
index 0000000..5115830
--- /dev/null
+++ b/src/platform/opengl/opengl_vertex_array.h
@@ -0,0 +1,41 @@
+#pragma once
+
+#include "core/memory.h"
+
+#include "rendering/vertex_array.h"
+#include "rendering/vertex_buffer.h"
+#include "rendering/index_buffer.h"
+
+#include <vector>
+
+namespace Donut
+{
+    class OpenGLVertexArray 
+        : public VertexArray 
+        {
+    public:
+        OpenGLVertexArray();
+        virtual ~OpenGLVertexArray();
+
+        virtual auto bind() const -> void override;
+        virtual auto unbind() const -> void override;
+
+        virtual auto add_vertex_buffer(const Ref<VertexBuffer>& vertex_buffer) -> void override;
+        virtual auto set_index_buffer(const Ref<IndexBuffer>& index_buffer) -> void override;
+
+        virtual const std::vector<Ref<VertexBuffer>>& get_vertex_buffers() const override 
+        { 
+            return m_vertex_buffers; 
+        }
+        
+        virtual const Ref<IndexBuffer>& get_index_buffer() const override 
+        { 
+            return m_index_buffer; 
+        }
+    private:
+        uint32_t m_renderer_id;
+        uint32_t m_vertex_buffer_index = 0;
+        std::vector<Ref<VertexBuffer>> m_vertex_buffers;
+        Ref<IndexBuffer>               m_index_buffer;
+    };
+};
diff --git a/src/platform/opengl/opengl_vertex_buffer.cpp b/src/platform/opengl/opengl_vertex_buffer.cpp
new file mode 100644
index 0000000..5cd4b82
--- /dev/null
+++ b/src/platform/opengl/opengl_vertex_buffer.cpp
@@ -0,0 +1,35 @@
+#include "opengl_vertex_buffer.h"
+#include "rendering/vertex_buffer.h"
+
+#include <glad/glad.h>
+
+namespace Donut 
+{
+    OpenGLVertexBuffer::OpenGLVertexBuffer(const void* data, uint32_t size)
+    {
+        glGenBuffers(1, &m_renderer_id); // glCreateBuffers is 4.5 DSA; unavailable on macOS 4.1
+        glBindBuffer(GL_ARRAY_BUFFER, m_renderer_id);
+        glBufferData(GL_ARRAY_BUFFER, size, data, GL_STATIC_DRAW);
+    }
+
+    OpenGLVertexBuffer::~OpenGLVertexBuffer()
+    {
+        glDeleteBuffers(1, &m_renderer_id);
+    }
+
+    auto OpenGLVertexBuffer::bind() const -> void
+    {
+        glBindBuffer(GL_ARRAY_BUFFER, m_renderer_id);
+    }
+
+    auto OpenGLVertexBuffer::unbind() const -> void
+    {
+        glBindBuffer(GL_ARRAY_BUFFER, 0);
+    }
+
+    auto OpenGLVertexBuffer::set_data(const void* data, uint32_t size) -> void
+    {
+        glBindBuffer(GL_ARRAY_BUFFER, m_renderer_id);
+        glBufferSubData(GL_ARRAY_BUFFER, 0, size, data);
+    }
+};
diff --git a/src/platform/opengl/opengl_vertex_buffer.h b/src/platform/opengl/opengl_vertex_buffer.h
new file mode 100644
index 0000000..df2e0e6
--- /dev/null
+++ b/src/platform/opengl/opengl_vertex_buffer.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#include "rendering/vertex_buffer.h"
+
+namespace Donut
+{
+    class OpenGLVertexBuffer
+        : public VertexBuffer 
+    {
+    public:
+        OpenGLVertexBuffer(const void* data, uint32_t size);
+        virtual ~OpenGLVertexBuffer();
+
+        virtual auto bind() const -> void override;
+        virtual auto unbind() const -> void override;
+        virtual auto set_data(const void* data, uint32_t size) -> void override;
+
+        virtual auto get_layout() const -> const VertexBufferLayout& override{ return m_layout;   }
+        virtual auto set_layout(const VertexBufferLayout& layout) -> void override{ m_layout = layout; }
+
+    private:
+        uint32_t           m_renderer_id;
+        VertexBufferLayout m_layout;
+    };
+};