fix(test_mesh): Use BOX floor instead of PLANE to fix shadow rendering

The issue was using ObjectType::PLANE with extreme non-uniform scaling
(20, 0.01, 20) which causes incorrect SDF distance calculations in shadows.

Following the pattern from test_3d_render.cc (which works correctly),
changed the floor to use ObjectType::BOX with:
- Position: vec3(0, -2, 0) (placed below ground level)
- Scale: vec3(25, 0.2, 25) (thin box, not extreme ratio)

This provides a proper floor surface without the shadow artifacts caused
by PLANE's distance field distortion under non-uniform scaling.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/tests/test_mesh.cc b/src/tests/test_mesh.cc
index f29ec27..8c64d9b 100644
--- a/src/tests/test_mesh.cc
+++ b/src/tests/test_mesh.cc
@@ -283,8 +283,9 @@ int main(int argc, char** argv) {
   g_renderer.set_noise_texture(g_textures.get_texture_view("noise"));
 
   // --- Create Scene ---
-  Object3D floor(ObjectType::PLANE);
-  floor.scale = vec3(20.0f, 0.01f, 20.0f); // Very thin floor proxy
+  Object3D floor(ObjectType::BOX);
+  floor.position = vec3(0, -2.0f, 0);
+  floor.scale = vec3(25.0f, 0.2f, 25.0f);
   floor.color = vec4(0.5f, 0.5f, 0.5f, 1.0f);
   g_scene.add_object(floor);