Expand internal splat scale encoding to e^[-12,9]. Lower zero cut-off to e^-30. Fix background color selection in editor. (#110)

src/PackedSplats.ts

@@ -51,7 +51,7 @@ export type PackedSplatsOptions = {
 // A PackedSplats is a collection of Gaussian splats, packed into a format that
 // takes exactly 16 bytes per Gsplat to maximize memory and cache efficiency.
 // The center xyz coordinates are encoded as float16 (3 x 2 bytes), scale xyz
-// as 3 x uint8 that encode a log scale from e^-9 to e^9, rgba as 4 x uint8,
+// as 3 x uint8 that encode a log scale from e^-12 to e^9, rgba as 4 x uint8,
 // and quaternion encoded via axis+angle using 2 x uint8 for octahedral encoding
 // of the axis direction and a uint8 to encode rotation amount from 0..Pi.
 

src/SparkRenderer.ts

@@ -105,7 +105,7 @@ export type SparkRendererOptions = {
   // any scale x/y/z component that is exactly 0 (minimum quantized value) results
   // in the other two non-0 axis being interpreted as an oriented 2D Gaussian Splat,
   // rather instead of the usual projected 3DGS Z-slice. When reading PLY files,
-  // scale values less than e^-20 will be interpreted as 0. (default: false)
+  // scale values less than e^-30 will be interpreted as 0. (default: false)
   enable2DGS?: boolean;
   // Scalar value to add to 2D splat covariance diagonal, effectively blurring +
   // enlarging splats. In scenes trained without the Gsplat anti-aliasing tweak

src/defines.ts

@@ -4,12 +4,15 @@
 // If these values are changed, the corresponding values in splatDefines.glsl
 // must also be updated to match.
 
-export const LN_SCALE_MIN = -9.0;
+export const LN_SCALE_MIN = -12.0;
 export const LN_SCALE_MAX = 9.0;
 export const LN_RESCALE = (LN_SCALE_MAX - LN_SCALE_MIN) / 254.0; // 1..=255
 export const SCALE_MIN = Math.exp(LN_SCALE_MIN);
 export const SCALE_MAX = Math.exp(LN_SCALE_MAX);
 
+export const LN_SCALE_ZERO = -30.0;
+export const SCALE_ZERO = Math.exp(LN_SCALE_ZERO);
+
 // Gsplats are stored in textures that are 2^11 x 2^11 x up to 2^11
 // Most WebGL2 implementations support 2D textures up to 2^12 x 2^12 (max 16M Gsplats)
 // 2D array textures and 3D textures up to 2^11 x 2^11 x 2^11 (max 8G Gsplats),

src/shaders/splatDefines.glsl

@@ -1,4 +1,4 @@
-const float LN_SCALE_MIN = -9.0;
+const float LN_SCALE_MIN = -12.0;
 const float LN_SCALE_MAX = 9.0;
 const float LN_RESCALE = (LN_SCALE_MAX - LN_SCALE_MIN) / 254.0; // 1..=255
 

src/utils.ts

@@ -6,6 +6,7 @@ import * as THREE from "three";
 import {
   LN_RESCALE,
   LN_SCALE_MIN,
+  SCALE_ZERO,
   SPLAT_TEX_HEIGHT,
   SPLAT_TEX_MIN_HEIGHT,
   SPLAT_TEX_WIDTH,
@@ -370,32 +371,32 @@ export function setPackedSplat(
 
   // Allow scales below LN_SCALE_MIN to be encoded as 0, which signifies a 2DGS
   const uScaleX =
-    scaleX === 0.0
+    scaleX < SCALE_ZERO
       ? 0
       : Math.min(
           255,
           Math.max(
-            0,
+            1,
             Math.round((Math.log(scaleX) - LN_SCALE_MIN) / LN_RESCALE) + 1,
           ),
         );
   const uScaleY =
-    scaleY === 0.0
+    scaleY < SCALE_ZERO
       ? 0
       : Math.min(
           255,
           Math.max(
-            0,
+            1,
             Math.round((Math.log(scaleY) - LN_SCALE_MIN) / LN_RESCALE) + 1,
           ),
         );
   const uScaleZ =
-    scaleZ === 0.0
+    scaleZ < SCALE_ZERO
       ? 0
       : Math.min(
           255,
           Math.max(
-            0,
+            1,
             Math.round((Math.log(scaleZ) - LN_SCALE_MIN) / LN_RESCALE) + 1,
           ),
         );
@@ -441,32 +442,32 @@ export function setPackedSplatScales(
 ) {
   // Allow scales below LN_SCALE_MIN to be encoded as 0, which signifies a 2DGS
   const uScaleX =
-    scaleX === 0.0
+    scaleX < SCALE_ZERO
       ? 0
       : Math.min(
           255,
           Math.max(
-            0,
+            1,
             Math.round((Math.log(scaleX) - LN_SCALE_MIN) / LN_RESCALE) + 1,
           ),
         );
   const uScaleY =
-    scaleY === 0.0
+    scaleY < SCALE_ZERO
       ? 0
       : Math.min(
           255,
           Math.max(
-            0,
+            1,
             Math.round((Math.log(scaleY) - LN_SCALE_MIN) / LN_RESCALE) + 1,
           ),
         );
   const uScaleZ =
-    scaleZ === 0.0
+    scaleZ < SCALE_ZERO
       ? 0
       : Math.min(
           255,
           Math.max(
-            0,
+            1,
             Math.round((Math.log(scaleZ) - LN_SCALE_MIN) / LN_RESCALE) + 1,
           ),
         );

src/worker.ts

@@ -1,7 +1,7 @@
 import init_wasm, { sort_splats } from "spark-internal-rs";
 import type { PcSogsJson, TranscodeSpzInput } from "./SplatLoader";
 import { unpackAntiSplat } from "./antisplat";
-import { SCALE_MIN, WASM_SPLAT_SORT } from "./defines";
+import { WASM_SPLAT_SORT } from "./defines";
 import { unpackKsplat } from "./ksplat";
 import { unpackPcSogs, unpackPcSogsZip } from "./pcsogs";
 import { PlyReader } from "./ply";
@@ -193,8 +193,6 @@ async function unpackPly({
   const numSplats = ply.numSplats;
 
   const extra: Record<string, unknown> = {};
-  // Anything below this is considered zero and can be rendered as 2DGS
-  const ZERO_CUTOFF = Math.exp(-20);
 
   ply.parseSplats(
     (
@@ -220,9 +218,9 @@ async function unpackPly({
         x,
         y,
         z,
-        scaleX < ZERO_CUTOFF ? 0 : Math.max(SCALE_MIN, scaleX),
-        scaleY < ZERO_CUTOFF ? 0 : Math.max(SCALE_MIN, scaleY),
-        scaleZ < ZERO_CUTOFF ? 0 : Math.max(SCALE_MIN, scaleZ),
+        scaleX,
+        scaleY,
+        scaleZ,
         quatX,
         quatY,
         quatZ,