fix(core): Fix the depth occlusion when developer explicitly set material.transparent=true.

Summary:
Softserve developer found that their app’s occlusion system failed for partially occluded materials because they set `transparent: false, opacity: 1`, overriding IWSDK’s `transparent: true` setup.

**Root Cause:**
- Depth occlusion relies on alpha modulation (`diffuseColor.a *= occlusion_value`), which only works if `material.transparent` is true.
- External code setting `transparent = false` (e.g., after placement animations) breaks occlusion, making occluded geometry fully opaque.

**Fix:**
- Discard fragments with `occlusion_value < 0.01` to always remove fully occluded geometry, regardless of the transparent flag.
- Soft edges remain when alpha blending is active; otherwise, edges degrade gracefully to hard.

Reviewed By: felixtrz

Differential Revision: D94739128

fbshipit-source-id: deb3221423b2f63130261eba30c727ad31007ecc

Author: zjm-meta

examples/depth-occlusion/src/index.js

@@ -218,10 +218,12 @@ World.create(document.getElementById('scene-container'), {
   // Register the depth sensing system with occlusion enabled
   world
     .registerSystem(DepthSensingSystem, {
-      enableDepthTexture: true,
-      enableOcclusion: true,
-      useFloat32: true,
-      blurRadius: 20.0,
+      configData: {
+        enableDepthTexture: true,
+        enableOcclusion: true,
+        useFloat32: true,
+        blurRadius: 20.0,
+      },
     })
     .registerComponent(DepthOccludable);
 

packages/core/src/depth/depth-sensing-system.ts

@@ -254,6 +254,9 @@ export class DepthSensingSystem extends createSystem(
           '   occlusion_value += OcclusionGetSample(depthUV, texelSize * vec2( 0.866, -0.5));',
           '   occlusion_value /= 13.0;',
           '  }',
+          '  if (occlusion_value < 0.01) {',
+          '      discard;',
+          '  }',
           '  diffuseColor.a *= occlusion_value;',
           '}',
         ].join('\n'),