Add modifiers normalColor and depthColor. Add examples/debug-color to show how to use them on SplatMeshes. (#58)

src/modifiers/depthColor.ts

@@ -0,0 +1,60 @@
+import type { SplatTransformer } from "../SplatGenerator";
+import type { SplatMesh } from "../SplatMesh";
+import {
+  type DynoVal,
+  Gsplat,
+  combineGsplat,
+  dynoBlock,
+  dynoConst,
+  neg,
+  normalizedDepth,
+  select,
+  split,
+  splitGsplat,
+  sub,
+} from "../dyno";
+
+export function makeDepthColorModifier(
+  splatToView: SplatTransformer,
+  minDepth: DynoVal<"float">,
+  maxDepth: DynoVal<"float">,
+  reverse: DynoVal<"bool">,
+) {
+  return dynoBlock({ gsplat: Gsplat }, { gsplat: Gsplat }, ({ gsplat }) => {
+    if (!gsplat) {
+      throw new Error("No gsplat input");
+    }
+    let { center } = splitGsplat(gsplat).outputs;
+    center = splatToView.apply(center);
+    const { z } = split(center).outputs;
+    let depth = normalizedDepth(neg(z), minDepth, maxDepth);
+    depth = select(reverse, sub(dynoConst("float", 1), depth), depth);
+
+    gsplat = combineGsplat({ gsplat, r: depth, g: depth, b: depth });
+    return { gsplat };
+  });
+}
+
+export function setDepthColor(
+  splats: SplatMesh,
+  minDepth: number,
+  maxDepth: number,
+  reverse?: boolean,
+) {
+  splats.enableWorldToView = true;
+  const dynoMinDepth = dynoConst("float", minDepth);
+  const dynoMaxDepth = dynoConst("float", maxDepth);
+  const dynoReverse = dynoConst("bool", reverse ?? false);
+  splats.worldModifier = makeDepthColorModifier(
+    splats.context.worldToView,
+    dynoMinDepth,
+    dynoMaxDepth,
+    dynoReverse,
+  );
+  splats.updateGenerator();
+  return {
+    minDepth: dynoMinDepth,
+    maxDepth: dynoMaxDepth,
+    reverse: dynoReverse,
+  };
+}