diff options
| author | hachem <im@hachem.wtf> | 2026-08-19 02:02:20 +0200 |
|---|---|---|
| committer | hachem <im@hachem.wtf> | 2026-08-19 02:02:20 +0200 |
| commit | f7e05555fb4ff6d8e51bdb5734db4dab1841d593 (patch) | |
| tree | 353d350b19da7b84ca11e5801d33a921407a963e /docs | |
| parent | 5c5fc10d8938fd2da1922f01c638d42e70eb1ab1 (diff) | |
[feat]: migrate to slang from glsl
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/configuration.md | 335 | ||||
| -rw-r--r-- | docs/mathematical-theory.md | 169 | ||||
| -rw-r--r-- | docs/numerical-methods.md | 50 | ||||
| -rw-r--r-- | docs/ray-tracing-implementation.md | 258 |
4 files changed, 0 insertions, 812 deletions
diff --git a/docs/configuration.md b/docs/configuration.md deleted file mode 100644 index 293a4a6..0000000 --- a/docs/configuration.md +++ /dev/null @@ -1,335 +0,0 @@ -# Configuration -## Configuration Files - -### Settings File Location - -The application uses TOML format for configuration files: - -- **Primary location**: `config/settings.toml` -- **User settings**: Loaded at startup, saved on exit - -### TOML Format - -The configuration uses TOML format: - -```toml -[simulation] -max_steps_static = 15000 -max_steps_moving = 30000 -compute_height = 256 -target_fps = 60 -early_exit_distance = 5e+12 -gravity_enabled = true - -[graphics] -render_api = "OpenGL" -vsync_enabled = true -enable_anti_aliasing = true -show_fps = true -show_performance_metrics = true -show_debug_info = false -selected_theme = "Dark" -``` - -## Simulation Parameters - -### Ray Tracing Settings - -#### Max Steps (Static) -- **Description**: Maximum number of integration steps when camera is stationary -- **Range**: 1,000 - 30,000 -- **Default**: 15,000 -- **Impact**: Higher values = better accuracy, lower performance - -```toml -max_steps_static = 15000 -``` - -#### Max Steps (Moving) -- **Description**: Maximum number of integration steps when camera is moving -- **Range**: 1,000 - 60,000 -- **Default**: 30,000 -- **Impact**: Higher values = smoother motion, lower performance - -```toml -max_steps_moving = 30000 -``` - -#### Early Exit Distance -- **Description**: Distance at which ray marching stops to improve performance -- **Range**: 1×10¹¹ - 1×10¹³ meters -- **Default**: 5×10¹² meters -- **Impact**: Lower values = faster rendering, may miss distant objects - -```toml -early_exit_distance = 5e+12 -``` - -### Performance Settings - -#### Target FPS -- **Description**: Target frame rate for the application -- **Range**: 30 - 120 FPS -- **Default**: 60 FPS -- **Impact**: Higher values = smoother animation, higher CPU usage - -```toml -target_fps = 60 -``` - -#### Compute Height -- **Description**: Resolution of the compute shader (height component) -- **Range**: 64 - 2,048 pixels -- **Default**: 256 pixels -- **Impact**: Higher values = better quality, lower performance - -```toml -compute_height = 256 -``` - -### Physics Settings - -#### Gravity Enabled -- **Description**: Enable/disable gravitational interactions between objects -- **Type**: Boolean -- **Default**: true -- **Impact**: Affects object motion and orbital dynamics - -```toml -gravity_enabled = true -``` - -## Graphics Settings - -### Rendering API - -#### Render API -- **Description**: Graphics API to use for rendering -- **Options**: "OpenGL", "Vulkan" -- **Default**: "OpenGL" -- **Impact**: Affects performance and feature availability - -```toml -render_api = "OpenGL" -``` - -### Display Settings - -#### V-Sync Enabled -- **Description**: Enable vertical synchronization -- **Type**: Boolean -- **Default**: true -- **Impact**: Prevents screen tearing, may limit frame rate - -```toml -vsync_enabled = true -``` - -#### Enable Anti-Aliasing -- **Description**: Enable anti-aliasing for smoother edges -- **Type**: Boolean -- **Default**: true -- **Impact**: Better visual quality, slight performance cost - -```toml -enable_anti_aliasing = true -``` - -### UI Settings - -#### Show FPS -- **Description**: Display frame rate counter -- **Type**: Boolean -- **Default**: true -- **Impact**: Performance monitoring, minimal overhead - -```toml -show_fps = true -``` - -#### Show Performance Metrics -- **Description**: Display detailed performance information -- **Type**: Boolean -- **Default**: true -- **Impact**: Debug information, minimal overhead - -```toml -show_performance_metrics = true -``` - -#### Show Debug Info -- **Description**: Display debug information -- **Type**: Boolean -- **Default**: false -- **Impact**: Development information, may impact performance - -```toml -show_debug_info = false -``` - -#### Selected Theme -- **Description**: UI theme selection -- **Options**: "Dark", "Light" -- **Default**: "Dark" -- **Impact**: Visual appearance only - -```toml -selected_theme = "Dark" -``` - -## Performance Tuning - -### Preset-Performance - -The configuration system allows users to balance quality and performance: - -#### High Quality Settings -```toml -[simulation] -max_steps_static = 30000 -max_steps_moving = 60000 -compute_height = 1024 -early_exit_distance = 1e+13 -``` - -#### Balanced Settings -```toml -[simulation] -max_steps_static = 15000 -max_steps_moving = 30000 -compute_height = 512 -early_exit_distance = 5e+12 -``` - -#### Performance Settings -```toml -[simulation] -max_steps_static = 5000 -max_steps_moving = 10000 -compute_height = 256 -early_exit_distance = 2e+12 -``` - -### Adaptive Performance - -The application automatically adjusts performance based on conditions: - -```glsl -// Reduce steps for distant cameras -float cameraDistance = length(cam.camPos); -if (cameraDistance > 2e12) - maxSteps = maxSteps / 2; -else if (cameraDistance > 1e12) - maxSteps = int(maxSteps * 0.75); - -// Reduce steps for escaping rays -float initialEscapeVelocity = sqrt(2.0 * SagA_rs / ray.r); -if (ray.dr > initialEscapeVelocity * 0.95 && ray.r > SagA_rs * 200.0) - maxSteps = maxSteps / 2; -``` - -## Configuration Interface - -### GUI Configuration - -The application provides a graphical interface for configuration: - -```cpp -void ConfigState::OnImGuiRender() -{ - ImGui::Begin("Configuration"); - - // Simulation settings - ImGui::TextColored(ImVec4(0.9f, 0.9f, 1.0f, 1.0f), "Simulation"); - ImGui::Separator(); - - ImGui::SliderInt("Max Steps (Static)", &m_MaxStepsStatic, 1000, 30000, "%d"); - ImGui::SliderInt("Max Steps (Moving)", &m_MaxStepsMoving, 1000, 60000, "%d"); - ImGui::SliderFloat("Early Exit Distance", &m_EarlyExitDistance, 1e11f, 1e13f, "%.2e"); - ImGui::SliderInt("Compute Height", &m_ComputeHeight, 64, 2048, "%d px"); - ImGui::SliderInt("Target FPS", &m_TargetFPS, 30, 120, "%d"); - - // Physics settings - ImGui::TextColored(ImVec4(0.9f, 0.9f, 1.0f, 1.0f), "Physics"); - ImGui::Separator(); - - ImGui::Checkbox("Enable Gravity", &m_GravityEnabled); - - // Graphics settings - ImGui::TextColored(ImVec4(0.9f, 0.9f, 1.0f, 1.0f), "Graphics"); - ImGui::Separator(); - - ImGui::Checkbox("V-Sync", &m_VSyncEnabled); - ImGui::Checkbox("Anti-Aliasing", &m_AntiAliasingEnabled); - ImGui::Checkbox("Show FPS", &m_ShowFPS); - ImGui::Checkbox("Performance Metrics", &m_ShowPerformanceMetrics); - - ImGui::End(); -} -``` - - -## Default Configurations - -### Preset Configurations - -The application includes several preset configurations: - -#### Ultra Quality -```toml -[simulation] -max_steps_static = 50000 -max_steps_moving = 100000 -compute_height = 2048 -early_exit_distance = 1e+13 -target_fps = 30 -``` - -#### High Quality -```toml -[simulation] -max_steps_static = 30000 -max_steps_moving = 60000 -compute_height = 1024 -early_exit_distance = 8e+12 -target_fps = 60 -``` - -#### Balanced -```toml -[simulation] -max_steps_static = 15000 -max_steps_moving = 30000 -compute_height = 512 -early_exit_distance = 5e+12 -target_fps = 60 -``` - -#### Performance -```toml -[simulation] -max_steps_static = 5000 -max_steps_moving = 10000 -compute_height = 256 -early_exit_distance = 2e+12 -target_fps = 120 -``` - -## Troubleshooting - -### Common Issues - -#### Performance Problems -- **Symptom**: Low frame rate, stuttering -- **Solution**: Reduce `max_steps_moving`, `max_steps_static`, or `compute_height` -- **Alternative**: Increase `early_exit_distance` - -#### Quality Issues -- **Symptom**: Poor image quality, artifacts -- **Solution**: Increase `compute_height` and step counts -- **Alternative**: Reduce `early_exit_distance` - -#### Configuration Errors -- **Symptom**: Application crashes on startup -- **Solution**: Delete configuration file to reset to defaults -- **Alternative**: Check TOML syntax in settings file
\ No newline at end of file diff --git a/docs/mathematical-theory.md b/docs/mathematical-theory.md deleted file mode 100644 index 4c73425..0000000 --- a/docs/mathematical-theory.md +++ /dev/null @@ -1,169 +0,0 @@ -# Mathematical Theory of Black Hole Geodesics - -### Einstein’s Field Equations - -General Relativity describes gravity not as a force, but as the curvature of spacetime caused by mass and energy. This curvature is captured by **Einstein’s field equations**: - -$$ -G_{\mu\nu} = \frac{8\pi G}{c^4} T_{\mu\nu} -$$ - -Here: - -* $G_{\mu\nu}$ is the **Einstein tensor**, describing spacetime curvature. -* $T_{\mu\nu}$ is the **stress-energy tensor**, representing matter and energy. -* $G$ is Newton’s gravitational constant, and $c$ is the speed of light. - -### Spacetime Metric - -Distances in spacetime are described using the **metric tensor** $g_{\mu\nu}$: - -$$ -ds^2 = g_{\mu\nu} dx^\mu dx^\nu -$$ - -where $ds^2$ is the spacetime interval between two events. - -## Schwarzschild Metric - -For a **spherically symmetric, non-rotating mass** (like a static black hole), the Schwarzschild solution gives the spacetime geometry: - -$$ -ds^2 = -\left(1 - \frac{2GM}{c^2 r}\right) dt^2 + \left(1 - \frac{2GM}{c^2 r}\right)^{-1} dr^2 + r^2 (d\theta^2 + \sin^2\theta \, d\phi^2) -$$ - -* $M$ = mass of the black hole -* $r, \theta, \phi$ = spherical coordinates -* $t$ = time coordinate - -The **Schwarzschild radius** $r_s$ marks the event horizon: - -$$ -r_s = \frac{2GM}{c^2} -$$ - -Inside $r_s$, not even light can escape. - -We often write the metric using the **lapse function** $f(r)$: - -$$ -ds^2 = -f(r) dt^2 + f(r)^{-1} dr^2 + r^2 (d\theta^2 + \sin^2\theta \, d\phi^2), \quad f(r) = 1 - \frac{r_s}{r} -$$ - -## Geodesics: Paths of Free-Falling Particles and Light - -A **geodesic** is the path that a particle follows when moving under gravity alone. For light rays, $ds^2 = 0$ (null geodesics). - -### Lagrangian Formulation - -We can derive the geodesic equations from a Lagrangian: - -$$ -L = \frac{1}{2} g_{\mu\nu} \dot{x}^\mu \dot{x}^\nu, \quad \dot{x}^\mu = \frac{dx^\mu}{d\lambda} -$$ - -where $\lambda$ is an affine parameter along the geodesic. - -### Conserved Quantities - -Because the Schwarzschild metric is **time-independent** and **spherically symmetric**, we have two key conserved quantities: - -1. **Energy** (from time translation symmetry): - -$$ -E = - g_{tt} \frac{dt}{d\lambda} = f(r) \frac{dt}{d\lambda} -$$ - -2. **Angular Momentum** (from rotational symmetry): - -$$ -L = g_{\phi\phi} \frac{d\phi}{d\lambda} = r^2 \sin^2 \theta \frac{d\phi}{d\lambda} -$$ - -### Derivation of the Geodesic Equations - -Geodesics satisfy the **Euler-Lagrange equations**: - -$$ -\frac{d}{d\lambda} \left(\frac{\partial L}{\partial \dot{x}^\mu}\right) - \frac{\partial L}{\partial x^\mu} = 0 -$$ - -#### 1. Radial Motion - -For the Schwarzschild metric: - -$$ -L = \frac{1}{2} \left[-f(r) \dot{t}^2 + f(r)^{-1} \dot{r}^2 + r^2 (\dot{\theta}^2 + \sin^2\theta \, \dot{\phi}^2)\right] -$$ - -The radial Euler-Lagrange equation becomes: - -$$ -\ddot{r} = -\frac{GM}{r^2} (\dot{t})^2 + \frac{GM}{r^2 f(r)} (\dot{r})^2 + r f(r) \left(\dot{\theta}^2 + \sin^2\theta \, \dot{\phi}^2\right) -$$ - -#### 2. Angular Motion - -$$ -\ddot{\theta} = -\frac{2}{r} \dot{r} \dot{\theta} + \sin\theta \cos\theta \, \dot{\phi}^2 -$$ - -$$ -\ddot{\phi} = -\frac{2}{r} \dot{r} \dot{\phi} - 2 \cot\theta \, \dot{\theta} \dot{\phi} -$$ - -Here, $\dot{}$ denotes derivative with respect to $\lambda$. - -These equations fully describe how light or particles move around a Schwarzschild black hole. - -### Numerical Implementation - -In a shader or simulation, we integrate these equations using: - -```glsl -void GeodesicRHS(Ray ray, out vec3 d1, out vec3 d2) -{ - float r = ray.r; - float theta = ray.theta; - float dr = ray.dr; - float dtheta = ray.dtheta; - float dphi = ray.dphi; - float f = 1.0 - SagA_rs / r; - float dt_dL = ray.E / f; - - d1 = vec3(dr, dtheta, dphi); - d2.x = - (SagA_rs / (2.0 * r*r)) * f * dt_dL * dt_dL - + (SagA_rs / (2.0 * r*r * f)) * dr * dr - + r * (dtheta*dtheta + sin(theta)*sin(theta)*dphi*dphi); - d2.y = -2.0*dr*dtheta/r + sin(theta)*cos(theta)*dphi*dphi; - d2.z = -2.0*dr*dphi/r - 2.0*cos(theta)/(sin(theta)) * dtheta * dphi; -} -``` - -### Conserved Quantities in Code - -```glsl -ray.E = f * dt_dL; // Energy -ray.L = ray.r * ray.r * sin(ray.theta) * ray.dphi; // Angular momentum -``` - -### Effective Potential - -The **radial motion** can be described using an effective potential: - -$$ -V_\text{eff}(r) = \left(1 - \frac{r_s}{r}\right) \frac{L^2}{r^2} -$$ - -This potential defines the possible orbits of light or particles. - -### Relativistic Effects Around Black Holes - -* **Gravitational Lensing:** Light bends around the black hole, producing Einstein rings, multiple images, or distorted images. -* **Event Horizon:** Located at $r = r_s$, where nothing escapes. -* **Photon Sphere:** At $r = 1.5 r_s$, light can orbit in unstable circular paths. - -### Numerical Considerations - -* **Event Horizon:** Integration becomes singular at $r = r_s$. Use adaptive step sizes or terminate integration near the horizon. -* **Coordinate Poles:** Spherical coordinates have singularities at $\theta = 0, \pi$. Avoid direct integration through these points or use transformations. diff --git a/docs/numerical-methods.md b/docs/numerical-methods.md deleted file mode 100644 index 4e102e6..0000000 --- a/docs/numerical-methods.md +++ /dev/null @@ -1,50 +0,0 @@ -## Runge-Kutta 4 (RK4) Integration — Explained - -When we talk about geodesics in curved spacetime, we’re dealing with a system of differential equations that describe how a particle—or in our case, a ray of light—moves. These equations are usually too complicated to solve exactly, so we turn to numerical methods. One of the most popular choices is the **fourth-order Runge-Kutta method (RK4)**. - -Think of RK4 like taking careful steps along a winding mountain trail. At each step, instead of just looking straight ahead, RK4 takes a few “sneak peeks” along the way to estimate the path more accurately. - -### The Idea in Simple Terms - -Suppose you know where you are at a particular moment and you know the slope of your path (the derivative). A naive method like **Euler’s method** would take a single step using that slope and call it a day. But if the slope changes a lot along your step, Euler can easily go off-track. - -RK4 improves on this by taking **four evaluations** of the slope at carefully chosen points: - -1. **Start of the step** — check the slope right where you are (`k1`). -2. **Halfway in, using the first slope** — imagine taking a mid-step to see if the slope changes (`k2`). -3. **Halfway in, using the second slope** — another mid-step with a slightly better estimate (`k3`). -4. **End of the step** — take a peek at the slope at the far end of your step (`k4`). - -Then RK4 combines all these slopes in a weighted average: - -$$ -y_{n+1} = y_n + \frac{h}{6} (k_1 + 2 k_2 + 2 k_3 + k_4) -$$ - -This weighted combination gives a very accurate estimate of where you should be at the next step. - -### Why RK4 Works Well for Geodesics - -In the context of geodesics: - -* Each ray has six “pieces of information”: position `(r, θ, φ)` and velocity `(dr/dλ, dθ/dλ, dφ/dλ)`. -* The RK4 method allows us to update all six components **simultaneously**, while keeping the accumulated error small. -* Because spacetime curvature can change dramatically near a black hole, RK4 is especially helpful: it’s stable enough to handle strong curvature without requiring tiny steps everywhere. - -### A Visual Analogy - -Imagine you’re rowing a boat down a twisting river: - -* **Euler**: You look at the current direction, row a fixed distance, and hope for the best. You’ll likely drift off course if the river bends sharply. -* **RK4**: You peek ahead four times along your intended path and adjust your stroke accordingly. You stay much closer to the true river path, even around tight bends. - -### Accuracy - -* RK4 is called **fourth-order** because the error per step scales with $h^5$, and the total accumulated error scales roughly with $h^4$ (where $h$ is your step size). -* This means you can take reasonably large steps without losing accuracy, which is critical when simulating millions of rays efficiently. - -### Connecting to Code - -In your code, each `k` evaluation corresponds to calculating how the ray’s position and velocity would change at different “guesses” along the step. The final weighted combination moves the ray forward accurately in spacetime. - -By using RK4, we’re essentially giving each ray a **very careful and informed nudge**, instead of blindly pushing it along, which is why the results are both stable and accurate—even near the extreme curvature of a black hole.
\ No newline at end of file diff --git a/docs/ray-tracing-implementation.md b/docs/ray-tracing-implementation.md deleted file mode 100644 index 89778b7..0000000 --- a/docs/ray-tracing-implementation.md +++ /dev/null @@ -1,258 +0,0 @@ -# Ray Tracing in Curved Spacetime: A Detailed Overview - -This ray tracer simulates how light behaves near a black hole, including the effects of curved spacetime and interactions with objects like stars and an accretion disk. The implementation follows a step-by-step approach, which includes initializing rays, tracing their paths through spacetime, detecting intersections with objects, and finally rendering the scene. - -## 1. Ray Initialization - -The first step in ray tracing is to create rays originating from the camera that will eventually traverse through spacetime. Each ray represents a possible path of light. - -### Camera Setup - -The camera is positioned in three-dimensional space and is defined by its orientation and field of view. It has the following parameters: - -```glsl -layout(std140, binding = 1) uniform Camera -{ - vec3 camPos; float _pad0; - vec3 camRight; float _pad1; - vec3 camUp; float _pad2; - vec3 camForward; float _pad3; - float tanHalfFov; // Field of view - float aspect; // Aspect ratio - bool moving; // Whether the camera is moving - int _pad4; -} cam; -``` - -- `camPos`: The 3D position of the camera. -- `camRight`, `camUp`, `camForward`: Orthonormal vectors defining the camera's orientation. -- `tanHalfFov` and `aspect`: Determine the camera’s field of view and the shape of the image plane. - -### Ray Generation per Pixel - -For each pixel on the image, we calculate the corresponding direction in world space and generate a ray pointing in that direction: - -```glsl -float u = (2.0 * (pix.x + 0.5) / WIDTH - 1.0) * cam.aspect * cam.tanHalfFov; -float v = (1.0 - 2.0 * (pix.y + 0.5) / HEIGHT) * cam.tanHalfFov; -vec3 dir = normalize(u * cam.camRight - v * cam.camUp + cam.camForward); -Ray ray = InitRay(cam.camPos, dir); -``` - -Here, `u` and `v` are normalized coordinates on the image plane. The `InitRay` function takes the camera position and the computed direction to create a ray in both Cartesian and spherical coordinates. - -### Ray Structure - -Each ray contains not only the standard 3D Cartesian position but also spherical coordinates and velocity components, which are necessary for simulating curved spacetime: - -```glsl -struct Ray -{ - float x, y, z; // Cartesian coordinates - float r, theta, phi; // Spherical coordinates - float dr, dtheta, dphi; // Radial and angular velocities - float E, L; // Conserved quantities in Schwarzschild geometry -}; -``` - -### Converting Cartesian to Spherical Coordinates - -The `InitRay` function converts the position and direction of the ray into spherical coordinates and computes initial velocities: - -```glsl -Ray InitRay(vec3 pos, vec3 dir) -{ - Ray ray; - ray.x = pos.x; - ray.y = pos.y; - ray.z = pos.z; - - // Spherical coordinates - ray.r = length(pos); - ray.theta = acos(pos.z / ray.r); - ray.phi = atan(pos.y, pos.x); - - // Convert direction vector to spherical velocities - float dx = dir.x; - float dy = dir.y; - float dz = dir.z; - - ray.dr = sin(ray.theta)*cos(ray.phi)*dx + sin(ray.theta)*sin(ray.phi)*dy + cos(ray.theta)*dz; - ray.dtheta = (cos(ray.theta)*cos(ray.phi)*dx + cos(ray.theta)*sin(ray.phi)*dy - sin(ray.theta)*dz) / ray.r; - ray.dphi = (-sin(ray.phi)*dx + cos(ray.phi)*dy) / (ray.r * sin(ray.theta)); - - // Calculate conserved quantities (energy E and angular momentum L) - ray.L = ray.r * ray.r * sin(ray.theta) * ray.dphi; - float f = 1.0 - SagA_rs / ray.r; - float dt_dL = sqrt((ray.dr*ray.dr)/f + ray.r*ray.r*(ray.dtheta*ray.dtheta + sin(ray.theta)*sin(ray.theta)*ray.dphi*ray.dphi)); - ray.E = f * dt_dL; - - return ray; -} -``` - -## 2. Geodesic Integration - -Once the ray is initialized, we trace its path through curved spacetime using the Schwarzschild metric. This requires solving the geodesic equations for the ray. - -### Integration Loop - -The ray is advanced step by step using a numerical integrator (Runge-Kutta 4th order). The loop continues until the ray either escapes the scene, falls into the black hole, or intersects an object. - -```glsl -for (int i = 0; i < maxSteps; ++i) -{ - if (ray.r > exitDistance) break; - if (ray.r > ESCAPE_R) break; - if (Intercept(ray, SagA_rs)) { hitBlackHole = true; break; } - - currentStepSize = CalculateAdaptiveStepSize(ray, D_LAMBDA); - RK4Step(ray, currentStepSize); - lambda += currentStepSize; - - vec3 newPos = vec3(ray.x, ray.y, ray.z); - if (CrossesEquatorialPlane(prevPos, newPos)) { hitDisk = true; break; } - if (i % objectCheckInterval == 0 && InterceptObject(ray)) { hitObject = true; break; } - - prevPos = newPos; -} -``` - -### Runge-Kutta 4 (RK4) - -The RK4 integrator provides high accuracy by computing intermediate slopes and averaging them to advance the ray: - -```glsl -void RK4Step(inout Ray ray, float dL) -{ - vec3 k1a, k1b; - GeodesicRHS(ray, k1a, k1b); - - ray.r += dL * k1a.x; - ray.theta += dL * k1a.y; - ray.phi += dL * k1a.z; - ray.dr += dL * k1b.x; - ray.dtheta += dL * k1b.y; - ray.dphi += dL * k1b.z; - - // Update Cartesian coordinates - ray.x = ray.r * sin(ray.theta) * cos(ray.phi); - ray.y = ray.r * sin(ray.theta) * sin(ray.phi); - ray.z = ray.r * cos(ray.theta); -} -``` - -### Geodesic Derivatives - -The function `GeodesicRHS` computes the derivatives needed for integration: - -```glsl -void GeodesicRHS(Ray ray, out vec3 d1, out vec3 d2) -{ - float r = ray.r; - float theta = ray.theta; - float dr = ray.dr; - float dtheta = ray.dtheta; - float dphi = ray.dphi; - float f = 1.0 - SagA_rs / r; - float dt_dL = ray.E / f; - - d1 = vec3(dr, dtheta, dphi); - - d2.x = - (SagA_rs / (2.0 * r*r)) * f * dt_dL * dt_dL - + (SagA_rs / (2.0 * r*r * f)) * dr * dr - + r * (dtheta*dtheta + sin(theta)*sin(theta)*dphi*dphi); - d2.y = -2.0*dr*dtheta/r + sin(theta)*cos(theta)*dphi*dphi; - d2.z = -2.0*dr*dphi/r - 2.0*cos(theta)/(sin(theta)) * dtheta * dphi; -} -``` - -## 3. Intersection Testing - -Rays can intersect three types of entities: the black hole, spherical objects, and the accretion disk. - -### Black Hole Intersection - -A ray hitting the event horizon is considered absorbed: - -```glsl -bool Intercept(Ray ray, float rs) -{ - return ray.r <= rs; -} -``` - -### Object Intersection - -The scene can contain multiple spherical objects such as stars or planets: - -```glsl -bool InterceptObject(Ray ray) -{ - vec3 P = vec3(ray.x, ray.y, ray.z); - - for (int i = 0; i < numObjects; ++i) - { - vec3 center = objPosRadius[i].xyz; - float radius = objPosRadius[i].w; - - float distSq = dot(P - center, P - center); - if (distSq > radius * radius * 4.0) continue; - if (distSq <= radius * radius) - { - objectColor = objColor[i]; - hitCenter = center; - hitRadius = radius; - return true; - } - } - return false; -} -``` - -### Accretion Disk Intersection - -The accretion disk lies in the equatorial plane and is checked by detecting if the ray crosses this plane: - -```glsl -bool CrossesEquatorialPlane(vec3 oldPos, vec3 newPos) -{ - bool crossed = (oldPos.y * newPos.y <0.0); - if (crossed) { diskIntersection = newPos; } - return crossed; -} -``` - -## 4. Shading and Color Computation - -Once an intersection is found, we compute the color of the pixel based on the object hit and relativistic effects such as gravitational redshift and Doppler shift. - -```glsl -vec3 ComputeColor(Ray ray) -{ - if (hitBlackHole) return vec3(0.0); // Black hole is black - if (hitDisk) return SampleDiskTexture(diskIntersection); - if (hitObject) return ApplyLighting(ray, objectColor, hitCenter, hitRadius); - - return SampleBackground(ray); // Background stars, etc. -} -```` - -This ensures that each pixel reflects both the geometrical position and relativistic effects along the ray. - -## 5. Rendering Loop - -Finally, the main rendering loop iterates over every pixel on the screen, traces a ray, and stores the computed color: - -```glsl -for (int y = 0; y < HEIGHT; ++y) -{ - for (int x = 0; x < WIDTH; ++x) - { - Ray ray = InitRayForPixel(x, y); - TraceRay(ray); - vec3 color = ComputeColor(ray); - framebuffer[y*WIDTH + x] = vec4(color, 1.0); - } -} -```
\ No newline at end of file |
