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.

2 files changed, 13 insertions, 10 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;
 }
diff --git a/src/3d/renderer.cc b/src/3d/renderer.cc
index 6e8f38a..c37ea79 100644
--- a/src/3d/renderer.cc
+++ b/src/3d/renderer.cc
@@ -164,16 +164,15 @@ void Renderer3D::update_uniforms(const Scene& scene, const Camera& camera,
 
     data.color = obj.color;
     float type_id = 0.0f;
-    if (obj.type == ObjectType::SPHERE)
-      type_id = 1.0f;
-    else if (obj.type == ObjectType::BOX)
-      type_id = 2.0f;
-    else if (obj.type == ObjectType::TORUS)
-      type_id = 3.0f;
-    else if (obj.type == ObjectType::PLANE)
-      type_id = 4.0f;
-    else if (obj.type == ObjectType::MESH)
-      type_id = 5.0f;
+    switch (obj.type) {
+      case ObjectType::SPHERE: type_id = 1.0f; break;
+      case ObjectType::BOX:    type_id = 2.0f; break;
+      case ObjectType::CUBE:   type_id = 2.0f; break; // CUBE is same as BOX for shader
+      case ObjectType::TORUS:  type_id = 3.0f; break;
+      case ObjectType::PLANE:  type_id = 4.0f; break;
+      case ObjectType::MESH:   type_id = 5.0f; break;
+      default: type_id = 0.0f; break;
+    }
     data.params = vec4(type_id, obj.local_extent.x, obj.local_extent.y, obj.local_extent.z);
     obj_data.push_back(data);
     if (obj_data.size() >= kMaxObjects)