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Pre-compute lookup tables when parsing SOGS files #159

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merged 1 commit into from
Sep 15, 2025
Merged

Pre-compute lookup tables when parsing SOGS files #159

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133 changes: 84 additions & 49 deletions src/pcsogs.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -54,26 +54,39 @@ export async function unpackPcSogs(

const scalesPromise = decodeImageRgba(extraFiles[json.scales.files[0]]).then(
(scales) => {
const xLookup = new Array(256)
.fill(0)
.map(
(_, i) =>
json.scales.mins[0] +
(json.scales.maxs[0] - json.scales.mins[0]) * (i / 255),
)
.map((x) => Math.exp(x));
const yLookup = new Array(256)
.fill(0)
.map(
(_, i) =>
json.scales.mins[1] +
(json.scales.maxs[1] - json.scales.mins[1]) * (i / 255),
)
.map((x) => Math.exp(x));
const zLookup = new Array(256)
.fill(0)
.map(
(_, i) =>
json.scales.mins[2] +
(json.scales.maxs[2] - json.scales.mins[2]) * (i / 255),
)
.map((x) => Math.exp(x));

for (let i = 0; i < numSplats; ++i) {
const i4 = i * 4;
const fx = scales[i4 + 0] / 255;
const fy = scales[i4 + 1] / 255;
const fz = scales[i4 + 2] / 255;
const x =
json.scales.mins[0] +
(json.scales.maxs[0] - json.scales.mins[0]) * fx;
const y =
json.scales.mins[1] +
(json.scales.maxs[1] - json.scales.mins[1]) * fy;
const z =
json.scales.mins[2] +
(json.scales.maxs[2] - json.scales.mins[2]) * fz;
setPackedSplatScales(
packedArray,
i,
Math.exp(x),
Math.exp(y),
Math.exp(z),
xLookup[scales[i4 + 0]],
yLookup[scales[i4 + 1]],
zLookup[scales[i4 + 2]],
splatEncoding,
);
}
Expand All @@ -83,11 +96,15 @@ export async function unpackPcSogs(
const quatsPromise = decodeImageRgba(extraFiles[json.quats.files[0]]).then(
(quats) => {
const SQRT2 = Math.sqrt(2);
const lookup = new Array(256)
.fill(0)
.map((_, i) => (i / 255 - 0.5) * SQRT2);

for (let i = 0; i < numSplats; ++i) {
const i4 = i * 4;
const r0 = (quats[i4 + 0] / 255 - 0.5) * SQRT2;
const r1 = (quats[i4 + 1] / 255 - 0.5) * SQRT2;
const r2 = (quats[i4 + 2] / 255 - 0.5) * SQRT2;
const r0 = lookup[quats[i4 + 0]];
const r1 = lookup[quats[i4 + 1]];
const r2 = lookup[quats[i4 + 2]];
const rr = Math.sqrt(Math.max(0, 1.0 - r0 * r0 - r1 * r1 - r2 * r2));
const rOrder = quats[i4 + 3] - 252;
const quatX = rOrder === 0 ? r0 : rOrder === 1 ? rr : r1;
Expand All @@ -101,25 +118,50 @@ export async function unpackPcSogs(
const sh0Promise = decodeImageRgba(extraFiles[json.sh0.files[0]]).then(
(sh0) => {
const SH_C0 = 0.28209479177387814;
const rLookup = new Array(256)
.fill(0)
.map(
(_, i) =>
json.sh0.mins[0] +
(json.sh0.maxs[0] - json.sh0.mins[0]) * (i / 255),
)
.map((x) => SH_C0 * x + 0.5);
const gLookup = new Array(256)
.fill(0)
.map(
(_, i) =>
json.sh0.mins[1] +
(json.sh0.maxs[1] - json.sh0.mins[1]) * (i / 255),
)
.map((x) => SH_C0 * x + 0.5);
const bLookup = new Array(256)
.fill(0)
.map(
(_, i) =>
json.sh0.mins[2] +
(json.sh0.maxs[2] - json.sh0.mins[2]) * (i / 255),
)
.map((x) => SH_C0 * x + 0.5);
const aLookup = new Array(256)
.fill(0)
.map(
(_, i) =>
json.sh0.mins[3] +
(json.sh0.maxs[3] - json.sh0.mins[3]) * (i / 255),
)
.map((x) => 1.0 / (1.0 + Math.exp(-x)));

for (let i = 0; i < numSplats; ++i) {
const i4 = i * 4;
const f0 = sh0[i4 + 0] / 255;
const f1 = sh0[i4 + 1] / 255;
const f2 = sh0[i4 + 2] / 255;
const f3 = sh0[i4 + 3] / 255;
const dc0 =
json.sh0.mins[0] + (json.sh0.maxs[0] - json.sh0.mins[0]) * f0;
const dc1 =
json.sh0.mins[1] + (json.sh0.maxs[1] - json.sh0.mins[1]) * f1;
const dc2 =
json.sh0.mins[2] + (json.sh0.maxs[2] - json.sh0.mins[2]) * f2;
const opa =
json.sh0.mins[3] + (json.sh0.maxs[3] - json.sh0.mins[3]) * f3;
const r = SH_C0 * dc0 + 0.5;
const g = SH_C0 * dc1 + 0.5;
const b = SH_C0 * dc2 + 0.5;
const a = 1.0 / (1.0 + Math.exp(-opa));
setPackedSplatRgba(packedArray, i, r, g, b, a, splatEncoding);
setPackedSplatRgba(
packedArray,
i,
rLookup[sh0[i4 + 0]],
gLookup[sh0[i4 + 1]],
bLookup[sh0[i4 + 2]],
aLookup[sh0[i4 + 3]],
splatEncoding,
);
}
},
);
Expand All @@ -143,6 +185,10 @@ export async function unpackPcSogs(
decodeImage(extraFiles[json.shN.files[0]]),
decodeImage(extraFiles[json.shN.files[1]]),
]).then(([centroids, labels]) => {
const lookup = new Array(256)
.fill(0)
.map((_, i) => shN.mins + (shN.maxs - shN.mins) * (i / 255));

for (let i = 0; i < numSplats; ++i) {
const i4 = i * 4;
const label = labels.rgba[i4 + 0] + (labels.rgba[i4 + 1] << 8);
Expand All @@ -153,30 +199,19 @@ export async function unpackPcSogs(
for (let d = 0; d < 3; ++d) {
if (useSH1) {
for (let k = 0; k < 3; ++k) {
sh1[k * 3 + d] =
shN.mins +
((shN.maxs - shN.mins) * centroids.rgba[(offset + k) * 4 + d]) /
255;
sh1[k * 3 + d] = lookup[centroids.rgba[(offset + k) * 4 + d]];
}
}

if (useSH2) {
for (let k = 0; k < 5; ++k) {
sh2[k * 3 + d] =
shN.mins +
((shN.maxs - shN.mins) *
centroids.rgba[(offset + 3 + k) * 4 + d]) /
255;
sh2[k * 3 + d] = lookup[centroids.rgba[(offset + 3 + k) * 4 + d]];
}
}

if (useSH3) {
for (let k = 0; k < 7; ++k) {
sh3[k * 3 + d] =
shN.mins +
((shN.maxs - shN.mins) *
centroids.rgba[(offset + 8 + k) * 4 + d]) /
255;
sh3[k * 3 + d] = lookup[centroids.rgba[(offset + 8 + k) * 4 + d]];
}
}
}
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