feat(3d): Fix ObjectType::PLANE scaling and consolidate ObjectType mapping

- Implemented correct scaling for planes in both CPU (physics) and GPU (shaders) using the normal-axis scale factor.
- Consolidated ObjectType to type_id mapping in Renderer3D to ensure consistency and support for CUBE.
- Fixed overestimation of distance for non-uniformly scaled ground planes, which caused missing shadows.
- Updated documentation and marked Task A.2 as completed.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/3d/physics.cc b/src/3d/physics.cc
index 351dd06..229eb40 100644
--- a/src/3d/physics.cc
+++ b/src/3d/physics.cc
@@ -54,7 +54,11 @@ float PhysicsSystem::sample_sdf(const Object3D& obj, vec3 world_p) {
   float sx = vec3(model.m[0], model.m[1], model.m[2]).len();
   float sy = vec3(model.m[4], model.m[5], model.m[6]).len();
   float sz = vec3(model.m[8], model.m[9], model.m[10]).len();
+  
   float s = std::min(sx, std::min(sy, sz));
+  if (obj.type == ObjectType::PLANE) {
+    s = sy; // For plane with local normal (0,1,0), scale is sy
+  }
 
   return d * s;
 }