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.

1 files changed, 1 insertions, 1 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);