Externalize render settings minAlpha and maxPixelRadius (#130)

* Add commented benchmarkSort to compare JS vs Wasm sorting.

* Add 32-bit float sort via SparkViewpooint.sort32, using 2-pass radix-65536 sort. Turn on sort32 by default for examples/editor. Implemented Rust sort and JS sort, updated benchmarking code to include float16 and float32 sort.

* Add sort32 to docs/spark-viewpoint.md.

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

docs/docs/spark-renderer.md

@@ -57,6 +57,8 @@ const spark = new SparkRenderer({
 | **preUpdate**     | Controls whether to update the splats before or after rendering. For WebXR this *must* be false in order to complete rendering as soon as possible. (default: `false`)
 | **originDistance** | Distance threshold for `SparkRenderer` movement triggering a splat update at the new origin. (default: `1.0`) This can be useful when your `SparkRenderer` is a child of your camera and you want to retain high precision coordinates near the camera.
 | **maxStdDev**     | Maximum standard deviations from the center to render Gaussians. Values `Math.sqrt(5)`..`Math.sqrt(9)` produce good results and can be tweaked for performance. (default: `Math.sqrt(8)`)
+| **maxPixelRadius** | Maximum pixel radius for splat rendering. (default: `512.0`)
+| **minAlpha**      | Minimum alpha value for splat rendering. (default: `0.5 * (1.0 / 255.0)`)
 | **enable2DGS**    | Enable 2D Gaussian splatting rendering ability. When this mode is enabled, any `scale` x/y/z component that is exactly `0` (minimum quantized value) results in the other two non-zero axes being interpreted as an oriented 2D Gaussian Splat instead of the usual approximate projected 3DGS Z-slice. When reading PLY files, scale values less than e^-30 will be interpreted as `0`. (default: `false`)
 | **preBlurAmount** | Scalar value to add to 2D splat covariance diagonal, effectively blurring + enlarging splats. In scenes trained without the splat anti-aliasing tweak this value was typically 0.3, but with anti-aliasing it is 0.0 (default: `0.0`)
 | **blurAmount**    | Scalar value to add to 2D splat covariance diagonal, with opacity adjustment to correctly account for "blurring" when anti-aliasing. Typically 0.3 (equivalent to approx 0.5 pixel radius) in scenes trained with anti-aliasing.

examples/editor/index.html

@@ -515,6 +515,10 @@
       },
     }, "AA").name("AA preset");
     debugFolder.add(spark, "focalAdjustment", 0.1, 2.0, 0.1).name("Tweak focalAdjustment");
+    spark.defaultView.sort32 = true;
+    debugFolder.add(spark.defaultView, "sort32").name("Float32 sort").listen();
+    debugFolder.add(spark, "maxPixelRadius", 1, 1024, 1).name("Max pixel radius").listen();
+    debugFolder.add(spark, "minAlpha", 0, 1, 0.001).name("Min alpha").listen();
 
     const splatsFolder = secondGui.addFolder("Files");
 

src/SparkRenderer.ts

@@ -116,6 +116,16 @@ export type SparkRendererOptions = {
    * @default Math.sqrt(8)
    */
   maxStdDev?: number;
+  /**
+   * Maximum pixel radius for splat rendering.
+   * @default 512.0
+   */
+  maxPixelRadius?: number;
+  /**
+   * Minimum alpha value for splat rendering.
+   * @default 0.5 * (1.0 / 255.0)
+   */
+  minAlpha?: number;
   /**
    * Enable 2D Gaussian splatting rendering ability. When this mode is enabled,
    * any scale x/y/z component that is exactly 0 (minimum quantized value) results
@@ -185,6 +195,8 @@ export class SparkRenderer extends THREE.Mesh {
   preUpdate: boolean;
   originDistance: number;
   maxStdDev: number;
+  maxPixelRadius: number;
+  minAlpha: number;
   enable2DGS: boolean;
   preBlurAmount: number;
   blurAmount: number;
@@ -301,6 +313,8 @@ export class SparkRenderer extends THREE.Mesh {
     this.preUpdate = options.preUpdate ?? false;
     this.originDistance = options.originDistance ?? 1;
     this.maxStdDev = options.maxStdDev ?? Math.sqrt(8.0);
+    this.maxPixelRadius = options.maxPixelRadius ?? 512.0;
+    this.minAlpha = options.minAlpha ?? 0.5 * (1.0 / 255.0);
     this.enable2DGS = options.enable2DGS ?? false;
     this.preBlurAmount = options.preBlurAmount ?? 0.0;
     this.blurAmount = options.blurAmount ?? 0.3;
@@ -350,6 +364,10 @@ export class SparkRenderer extends THREE.Mesh {
       renderToViewPos: { value: new THREE.Vector3() },
       // Maximum distance (in stddevs) from Gsplat center to render
       maxStdDev: { value: 1.0 },
+      // Maximum pixel radius for splat rendering
+      maxPixelRadius: { value: 512.0 },
+      // Minimum alpha value for splat rendering
+      minAlpha: { value: 0.5 * (1.0 / 255.0) },
       // Enable interpreting 0-thickness Gsplats as 2DGS
       enable2DGS: { value: false },
       // Add to projected 2D splat covariance diagonal (thickens and brightens)
@@ -517,6 +535,8 @@ export class SparkRenderer extends THREE.Mesh {
     this.uniforms.far.value = typedCamera.far;
     this.uniforms.encodeLinear.value = viewpoint.encodeLinear;
     this.uniforms.maxStdDev.value = this.maxStdDev;
+    this.uniforms.maxPixelRadius.value = this.maxPixelRadius;
+    this.uniforms.minAlpha.value = this.minAlpha;
     this.uniforms.enable2DGS.value = this.enable2DGS;
     this.uniforms.preBlurAmount.value = this.preBlurAmount;
     this.uniforms.blurAmount.value = this.blurAmount;

src/shaders/splatDefines.glsl

@@ -21,10 +21,6 @@ const float PI = 3.1415926535897932384626433832795;
 const float INFINITY = 1.0 / 0.0;
 const float NEG_INFINITY = -INFINITY;
 
-const float MAX_PIXEL_RADIUS = 512.0;
-const float MIN_ALPHA = 0.5 * (1.0 / 255.0); // 0.00196
-const float MAX_STDDEV = sqrt(8.0);
-
 float sqr(float x) {
     return x * x;
 }

src/shaders/splatFragment.glsl

@@ -8,6 +8,7 @@ uniform float near;
 uniform float far;
 uniform bool encodeLinear;
 uniform float maxStdDev;
+uniform float minAlpha;
 uniform bool disableFalloff;
 uniform float falloff;
 
@@ -60,7 +61,7 @@ void main() {
 
     rgba.a *= mix(1.0, exp(-0.5 * z), falloff);
 
-    if (rgba.a < MIN_ALPHA) {
+    if (rgba.a < minAlpha) {
         discard;
     }
     if (encodeLinear) {

src/shaders/splatVertex.glsl

@@ -16,9 +16,11 @@ uniform uint numSplats;
 uniform vec4 renderToViewQuat;
 uniform vec3 renderToViewPos;
 uniform float maxStdDev;
+uniform float maxPixelRadius;
 uniform float time;
 uniform float deltaTime;
 uniform bool debugFlag;
+uniform float minAlpha;
 uniform bool enable2DGS;
 uniform float blurAmount;
 uniform float preBlurAmount;
@@ -52,7 +54,7 @@ void main() {
     vec4 quaternion, rgba;
     unpackSplat(packed, center, scales, quaternion, rgba);
 
-    if (rgba.a < MIN_ALPHA) {
+    if (rgba.a < minAlpha) {
         return;
     }
     bvec3 zeroScales = equal(scales, vec3(0.0));
@@ -141,13 +143,13 @@ void main() {
 
     float fullBlurAmount = blurAmount;
     if ((focalDistance > 0.0) && (apertureAngle > 0.0)) {
-        float focusRadius = MAX_PIXEL_RADIUS;
+        float focusRadius = maxPixelRadius;
         if (viewCenter.z < 0.0) {
             float focusBlur = abs((-viewCenter.z - focalDistance) / viewCenter.z);
             float apertureRadius = focal.x * tan(0.5 * apertureAngle);
             focusRadius = focusBlur * apertureRadius;
         }
-        fullBlurAmount = clamp(sqr(focusRadius), blurAmount, sqr(MAX_PIXEL_RADIUS));
+        fullBlurAmount = clamp(sqr(focusRadius), blurAmount, sqr(maxPixelRadius));
     }
 
     // Do convolution with a 0.5-pixel Gaussian for anti-aliasing: sqrt(0.3) ~= 0.5
@@ -159,7 +161,7 @@ void main() {
     // Compute anti-aliasing intensity scaling factor
     float blurAdjust = sqrt(max(0.0, detOrig / det));
     rgba.a *= blurAdjust;
-    if (rgba.a < MIN_ALPHA) {
+    if (rgba.a < minAlpha) {
         return;
     }
 
@@ -172,8 +174,8 @@ void main() {
     vec2 eigenVec1 = normalize(vec2((abs(b) < 0.001) ? 1.0 : b, eigen1 - a));
     vec2 eigenVec2 = vec2(eigenVec1.y, -eigenVec1.x);
 
-    float scale1 = position.x * min(MAX_PIXEL_RADIUS, maxStdDev * sqrt(eigen1));
-    float scale2 = position.y * min(MAX_PIXEL_RADIUS, maxStdDev * sqrt(eigen2));
+    float scale1 = position.x * min(maxPixelRadius, maxStdDev * sqrt(eigen1));
+    float scale2 = position.y * min(maxPixelRadius, maxStdDev * sqrt(eigen2));
 
     // Compute the NDC coordinates for the ellipsoid's diagonal axes.
     vec2 pixelOffset = eigenVec1 * scale1 + eigenVec2 * scale2;