Custom/extended splat encoding ranges, Premultiplied alpha for hyper-saturated colors (#134)

* Externalized SparkRenderer.maxPixelRadius and .minAlpha settings. Added to documentation. Added to examples/editor under Debug folder, moved sort32 there.

* Added SplatEncoding concept, applied individually to SparkRenderer (rgbMin/Max, lnScaleMinMax), SplatMesh (additionally sh1Min/Max, sh2, sh3). Updated examples/editor to control settings via gui. Updated all related code to pipe along settings where needed.
Added SparkRenderer.premultipliedAlpha to control blend mode and enable hyper-saturated color contributions by default.

* Fix SplatLoader not passing along encoding. Complete renaming to splat encoding.

src/dyno/output.ts

@@ -1,3 +1,4 @@
+import * as THREE from "three";
 import { Dyno, unindentLines } from "./base";
 import { Gsplat, defineGsplat } from "./splats";
 import {
@@ -7,30 +8,41 @@ import {
   type HasDynoOut,
 } from "./value";
 
-export const outputPackedSplat = (gsplat: DynoVal<typeof Gsplat>) =>
-  new OutputPackedSplat({ gsplat });
+export const outputPackedSplat = (
+  gsplat: DynoVal<typeof Gsplat>,
+  rgbMinMaxLnScaleMinMax: DynoVal<"vec4">,
+) => new OutputPackedSplat({ gsplat, rgbMinMaxLnScaleMinMax });
 export const outputRgba8 = (rgba8: DynoVal<"vec4">) =>
   new OutputRgba8({ rgba8 });
 
 export class OutputPackedSplat
-  extends Dyno<{ gsplat: typeof Gsplat }, { output: "uvec4" }>
+  extends Dyno<
+    { gsplat: typeof Gsplat; rgbMinMaxLnScaleMinMax: "vec4" },
+    { output: "uvec4" }
+  >
   implements HasDynoOut<"uvec4">
 {
-  constructor({ gsplat }: { gsplat?: DynoVal<typeof Gsplat> }) {
+  constructor({
+    gsplat,
+    rgbMinMaxLnScaleMinMax,
+  }: {
+    gsplat?: DynoVal<typeof Gsplat>;
+    rgbMinMaxLnScaleMinMax?: DynoVal<"vec4">;
+  }) {
     super({
-      inTypes: { gsplat: Gsplat },
-      inputs: { gsplat },
+      inTypes: { gsplat: Gsplat, rgbMinMaxLnScaleMinMax: "vec4" },
+      inputs: { gsplat, rgbMinMaxLnScaleMinMax },
       globals: () => [defineGsplat],
       statements: ({ inputs, outputs }) => {
         const { output } = outputs;
         if (!output) {
           return [];
         }
-        const { gsplat } = inputs;
+        const { gsplat, rgbMinMaxLnScaleMinMax } = inputs;
         if (gsplat) {
           return unindentLines(`
             if (isGsplatActive(${gsplat}.flags)) {
-              ${output} = packSplat(${gsplat}.center, ${gsplat}.scales, ${gsplat}.quaternion, ${gsplat}.rgba);
+              ${output} = packSplatEncoding(${gsplat}.center, ${gsplat}.scales, ${gsplat}.quaternion, ${gsplat}.rgba, ${rgbMinMaxLnScaleMinMax});
             } else {
               ${output} = uvec4(0u, 0u, 0u, 0u);
             }

src/dyno/splats.ts

@@ -118,6 +118,7 @@ export const definePackedSplats = unindent(`
   struct PackedSplats {
     usampler2DArray texture;
     int numSplats;
+    vec4 rgbMinMaxLnScaleMinMax;
   };
 `);
 
@@ -137,10 +138,10 @@ export class NumPackedSplats extends UnaryOp<
 }
 
 const defineReadPackedSplat = unindent(`
-  bool readPackedSplat(usampler2DArray texture, int numSplats, int index, out Gsplat gsplat) {
+  bool readPackedSplat(usampler2DArray texture, int numSplats, vec4 rgbMinMaxLnScaleMinMax, int index, out Gsplat gsplat) {
     if ((index >= 0) && (index < numSplats)) {
       uvec4 packed = texelFetch(texture, splatTexCoord(index), 0);
-      unpackSplat(packed, gsplat.center, gsplat.scales, gsplat.quaternion, gsplat.rgba);
+      unpackSplatEncoding(packed, gsplat.center, gsplat.scales, gsplat.quaternion, gsplat.rgba, rgbMinMaxLnScaleMinMax);
       return true;
     } else {
       return false;
@@ -173,7 +174,7 @@ export class ReadPackedSplat
         let statements: string[];
         if (packedSplats && index) {
           statements = unindentLines(`
-            if (readPackedSplat(${packedSplats}.texture, ${packedSplats}.numSplats, ${index}, ${gsplat})) {
+            if (readPackedSplat(${packedSplats}.texture, ${packedSplats}.numSplats, ${packedSplats}.rgbMinMaxLnScaleMinMax, ${index}, ${gsplat})) {
               bool zeroSize = all(equal(${gsplat}.scales, vec3(0.0, 0.0, 0.0)));
               ${gsplat}.flags = zeroSize ? 0u : GSPLAT_FLAG_ACTIVE;
             } else {
@@ -238,7 +239,7 @@ export class ReadPackedSplatRange
           statements = unindentLines(`
             ${gsplat}.flags = 0u;
             if ((${index} >= ${base}) && (${index} < (${base} + ${count}))) {
-              if (readPackedSplat(${packedSplats}.texture, ${packedSplats}.numSplats, ${index}, ${gsplat})) {
+              if (readPackedSplat(${packedSplats}.texture, ${packedSplats}.numSplats, ${packedSplats}.rgbMinMaxLnScaleMinMax, ${index}, ${gsplat})) {
                 bool zeroSize = all(equal(${gsplat}.scales, vec3(0.0, 0.0, 0.0)));
                 ${gsplat}.flags = zeroSize ? 0u : GSPLAT_FLAG_ACTIVE;
               }