fix(3d): Stabilize shadows and isolate floor grid texture

- Reverted floor to BOX (SDF) for robust shadow receipt.
- Updated shader to apply grid pattern ONLY to instance 0 (floor) or PLANE objects.
- Restored noise-based texturing for floating cubes and other SDF primitives.
- Verified that shadows and textures are now correctly applied across all scene elements.

2 files changed, 8 insertions, 8 deletions

diff --git a/src/3d/renderer.cc b/src/3d/renderer.cc
index d39aac0..abd98b6 100644
--- a/src/3d/renderer.cc
+++ b/src/3d/renderer.cc
@@ -254,7 +254,7 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
         normal = normalize(transpose(normal_matrix) * n_local);
 
         // Apply texture to SDF color
-        if (obj_type == 4.0) { // PLANE (used for floor)
+        if (in.instance_index == 0u || obj_type == 4.0) { // Floor (index 0) or PLANE
             let uv_grid = p.xz * 0.5;
             let grid = 0.5 + 0.5 * sin(uv_grid.x * 3.14) * sin(uv_grid.y * 3.14);
             let grid_val = smoothstep(0.45, 0.55, grid);
diff --git a/src/tests/test_3d_render.cc b/src/tests/test_3d_render.cc
index a6db71b..e1762ed 100644
--- a/src/tests/test_3d_render.cc
+++ b/src/tests/test_3d_render.cc
@@ -137,29 +137,29 @@ void setup_scene() {
   g_scene.clear();
   srand(12345); // Fixed seed
 
-  // Large floor, use PLANE type
-  Object3D floor(ObjectType::PLANE);
+  // Large floor, use BOX type (SDF) at index 0
+  Object3D floor(ObjectType::BOX);
   floor.position = vec3(0, -2.0f, 0);
-  floor.scale = vec3(25.0f, 1.0f, 25.0f); // Thicker for proxy hull safety
+  floor.scale = vec3(25.0f, 0.2f, 25.0f);
   floor.color = vec4(0.8f, 0.8f, 0.8f, 1.0f);
   g_scene.add_object(floor);
 
   // Large center Torus (SDF)
   Object3D center(ObjectType::TORUS);
   center.position = vec3(0, 1.0f, 0);
-  center.scale = vec3(2.5f, 2.5f, 2.5f); // Larger
+  center.scale = vec3(2.5f, 2.5f, 2.5f);
   center.color = vec4(1, 0.2, 0.2, 1);
   g_scene.add_object(center);
 
   // Moving Sphere (SDF)
   Object3D sphere(ObjectType::SPHERE);
   sphere.position = vec3(4.0f, 2.0f, 0);
-  sphere.scale = vec3(1.5f, 1.5f, 1.5f); // Larger
+  sphere.scale = vec3(1.5f, 1.5f, 1.5f);
   sphere.color = vec4(0.2, 1, 0.2, 1);
   g_scene.add_object(sphere);
 
   // Random objects
-  for (int i = 0; i < 30; ++i) { // More objects
+  for (int i = 0; i < 30; ++i) {
     ObjectType type = ObjectType::SPHERE;
     int r = rand() % 3;
     if (r == 1)
@@ -169,7 +169,7 @@ void setup_scene() {
 
     Object3D obj(type);
     float angle = (rand() % 360) * 0.01745f;
-    float dist = 3.0f + (rand() % 100) * 0.05f; // Closer to center
+    float dist = 3.0f + (rand() % 100) * 0.05f;
     float height = 0.5f + (rand() % 100) * 0.04f;
     obj.position = vec3(std::cos(angle) * dist, height, std::sin(angle) * dist);