Fix SOG SH decompression (#8271)

Author: slimbuck

src/framework/parsers/sog-bundle.js

@@ -268,6 +268,7 @@ class SogBundleParser {
             data.sh0 = textures[meta.sh0.files[0]].resource;
             data.sh_centroids = textures[meta.shN?.files[0]]?.resource;
             data.sh_labels = textures[meta.shN?.files[1]]?.resource;
+            data.shBands = GSplatSogsData.calcBands(data.sh_centroids?.width);
 
             if (!decompress) {
                 // no need to prepare gpu data if decompressing

src/framework/parsers/sogs.js

@@ -196,6 +196,7 @@ class SogsParser {
         data.sh0 = textures.sh0[0].resource;
         data.sh_centroids = textures.shN?.[0]?.resource;
         data.sh_labels = textures.shN?.[1]?.resource;
+        data.shBands = GSplatSogsData.calcBands(data.sh_centroids?.width);
 
         const decompress = asset.data?.decompress;
         const minimalMemory = asset.options?.minimalMemory ?? false;

src/scene/gsplat/gsplat-sogs-data.js

@@ -217,12 +217,11 @@ class GSplatSogsData {
     destroyed = false;
 
     /**
-     * Cached number of spherical harmonics bands.
+     * Number of spherical harmonics bands.
      *
      * @type {number}
-     * @private
      */
-    _shBands = 0;
+    shBands = 0;
 
     _destroyGpuResources() {
         this.means_l?.destroy();
@@ -237,6 +236,13 @@ class GSplatSogsData {
         this.packedShN?.destroy();
     }
 
+    // calculate the number of bands given the centroids texture width
+    static calcBands(centroidsWidth) {
+        // sh palette has 64 sh entries per row: 192 = 1 band (64*3), 512 = 2 bands (64*8), 960 = 3 bands (64*15)
+        const shBandsWidths = { 192: 1, 512: 2, 960: 3 };
+        return shBandsWidths[centroidsWidth] ?? 0;
+    }
+
     destroy() {
         // Remove devicerestored listener if it was registered
         this.deviceRestoredEvent?.off();
@@ -293,10 +299,6 @@ class GSplatSogsData {
         return true;
     }
 
-    get shBands() {
-        return this._shBands;
-    }
-
     async decompress() {
         const members = [
             'x', 'y', 'z',
@@ -543,11 +545,6 @@ class GSplatSogsData {
 
         if (this.destroyed || !device || device._destroyed) return;
 
-        // Cache shBands from sh_centroids texture width before source textures may be destroyed
-        // sh palette has 64 sh entries per row: 192 = 1 band (64*3), 512 = 2 bands (64*8), 960 = 3 bands (64*15)
-        const shBandsWidths = { 192: 1, 512: 2, 960: 3 };
-        this._shBands = shBandsWidths[this.sh_centroids?.width] ?? 0;
-
         // Include URL in texture name for debugging
         const urlSuffix = this.url ? `_${this.url}` : '';