fix: set GTAO thickness parameter and restore MRT normals

src/rendering/tsl/PostProcessing.ts

@@ -466,17 +466,15 @@ export class RenderPipeline {
         );
         outputNode = scenePassColor.mul(mix(float(1.0), aoValue, this.uAOIntensity));
       } else {
-        // Full-res AO - temporarily disabled normal pass to test if MRT normals
-        // are causing InstancedMesh artifacts. Passing null forces depth-based
-        // normal reconstruction.
+        // Full-res AO with scene normals for accurate occlusion
         const result = createGTAOPass(
           scenePassDepth,
           this.camera,
           {
             radius: this.config.aoRadius,
             intensity: this.config.aoIntensity,
           },
-          null // TODO: Fix InstancedMesh normal issue then restore scenePassNormal
+          scenePassNormal
         );
         if (result) {
           this.aoPass = result.pass;

src/rendering/tsl/effects/EffectPasses.ts

@@ -202,6 +202,11 @@ export function createGTAOPass(
     // The ao() function accepts null for normalNode even though types say otherwise
     const aoPass = ao(scenePassDepth, scenePassNormal ?? (null as any), camera);
     aoPass.radius.value = config.radius;
+    // Set thickness to help with depth discontinuity artifacts on InstancedMesh
+    // Higher thickness = more tolerance for depth differences = fewer edge artifacts
+    if (aoPass.thickness) {
+      aoPass.thickness.value = 0.5;
+    }
     const aoValueNode = aoPass.getTextureNode().r;
 
     return { pass: aoPass, aoValueNode };