feat(GS): harmonics and scaling of splats

src/loading2/gltf-splats-decoder.ts

@@ -102,7 +102,11 @@ export class GltfSplatDecoder implements GeometryDecoder {
       const fetchBuffer = async (url: string, offsetMultiplier: bigint): Promise<ArrayBuffer> => {
         const firstByte = byteOffset * 4n * offsetMultiplier;
         const lastByte = firstByte + byteSize * 4n * offsetMultiplier - 1n;
-        const headers: Record<string, string> = { Range: `bytes=${firstByte}-${lastByte}` };
+        const headers: any = {
+          Range: `bytes=${firstByte}-${lastByte}`,
+          'Transfer-Encoding': 'compress',
+          'Accept-Encoding': 'compress',
+        };
         const response = await this.xhrRequest(url, { headers });
         return response.arrayBuffer();
       };

src/loading2/gltf-splats-decoder.worker.js

@@ -179,7 +179,8 @@ onmessage = function (event) {
         // opacity
         let a = view.getFloat32(opacityOffset, true);
         a = (1 / (1 + Math.exp(-a))) * 255;
-        colors[c3] = clamp(Math.floor(a), 0, 255);
+        a = clamp(Math.floor(a), 0, 255);
+        colors[c3] = a;
       }
     } else if (['scale'].includes(pointAttribute.name)) {
       let maxScale = 0;

src/materials/shaders/splats.vert

@@ -4,6 +4,7 @@ precision highp int;
 uniform vec2 focal;
 uniform float inverseFocalAdjustment;
 uniform float splatScale;
+uniform float initialSplatScale;
 uniform vec2 basisViewport;
 uniform float harmonicsDegree;
 uniform bool renderIds;
@@ -277,7 +278,8 @@ void main() {
 
     if(adaptiveSize) {
         float lodSplatScale = clamp(getLOD( nodePosition, int(vnStart), float(level) ) / maxDepth, 0., 1.);
-        renderScale = mix(maxSplatScale * splatScale, 1., lodSplatScale);
+        float currentSplatScale = lodSplatScale < 2. ? initialSplatScale : splatScale;
+        renderScale = mix(maxSplatScale * currentSplatScale, 1., lodSplatScale);
     }
 
     vRenderScale = renderScale;
@@ -302,7 +304,9 @@ void main() {
 
     vColor = colorData.rgb;
 
-    vec3 worldViewDir = normalize(-viewCenter.rgb);
+    vec4 worldCenter = modelMatrix * vec4(instancePosition, 1.0);
+
+    vec3 worldViewDir = normalize(worldCenter.xyz - cameraPosition);
 
     //Harmonics
     vec3 harmonics = vec3(0.);

src/splats-mesh.ts

@@ -240,6 +240,7 @@ export class SplatsMesh extends Object3D {
           focal: { value: new Vector2(0, 0) },
           inverseFocalAdjustment: { value: 1 },
           splatScale: { value: 1 },
+          initialSplatScale: { value: 1 },
           basisViewport: { value: new Vector2(0, 0) },
           globalOffset: { value: new Vector3(0, 0, 0) },
           sortedTexture: { value: null },