[feat]: wire in scene into the simulation engine

3 files changed, 11 insertions, 4 deletions

diff --git a/src/scene/scene.cpp b/src/scene/scene.cpp
index db70a8d..b8ab005 100644
--- a/src/scene/scene.cpp
+++ b/src/scene/scene.cpp
@@ -23,8 +23,8 @@ namespace Donut
         // Scene camera: normal-scale orbital world-builder viewer.
         scene_camera.set_camera_mode(CameraMode::Orbital);
         scene_camera.set_orbital_target(glm::vec3(0.0f));
-        scene_camera.set_orbital_radius(15.0);
-        scene_camera.set_orbital_limits(2.0, 200.0);
+        scene_camera.set_orbital_radius(30.0);   // frame the hole + orbiting objects (in r_s)
+        scene_camera.set_orbital_limits(3.0, 400.0);
         scene_camera.set_orbital_speed(0.01f);
         scene_camera.set_zoom_speed(2.0);
         scene_camera.set_azimuth(0.0f);
diff --git a/src/scene/scene.h b/src/scene/scene.h
index 27d1327..23d884f 100644
--- a/src/scene/scene.h
+++ b/src/scene/scene.h
@@ -17,8 +17,9 @@ namespace Donut
     public:
         Scene();
 
-        // world-builder content
-        std::vector<SceneObject> objects{ SceneObject{} };
+        // world-builder content. The default object orbits clear of the hole at the
+        // origin (positions are in Schwarzschild radii; see BH_SCENE_RADIUS).
+        std::vector<SceneObject> objects{ SceneObject{ { 18.0f, 6.0f, 0.0f }, 2.0f, { 0.85f, 0.35f, 0.2f } } };
         int selected_object = 0;
 
         // black hole / accretion disk
diff --git a/src/scene/scene_types.h b/src/scene/scene_types.h
index d34983f..61bea35 100644
--- a/src/scene/scene_types.h
+++ b/src/scene/scene_types.h
@@ -8,6 +8,12 @@ namespace Donut
     // portable renderers (SceneRenderer, BlackHoleRenderer). The rendering itself
     // is written once on the RHI (rendering/rhi.h); these are just the inputs.
 
+    // The scene editor and the simulation share ONE world at this scale: this many
+    // grid units == one Schwarzschild radius. The SceneRenderer draws the hole's
+    // horizon at this radius; the BlackHoleRenderer maps scene positions into
+    // physical units (x SagA_rs / SCENE_UNITS_PER_RS) so placed objects line up.
+    constexpr float SCENE_UNITS_PER_RS = 3.0f;
+
     // A placeable/editable sphere in the world-builder scene view. The app owns
     // the list; SceneRenderer draws it the same way on every backend.
     struct SceneObject