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31c7d49 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 | import type { GaussianAttributes } from '../ImageToGaussianModel'
export const TRIPOSPLAT_GAUSSIANS_PER_POINT = 32
export const TRIPOSPLAT_GS_FEATURE_WIDTH = 480
const XYZ_START = 0
const DC_START = 96
const SCALING_START = 192
const ROTATION_START = 288
const OPACITY_START = 416
const OFFSET_SCALE_START = 448
const OFFSET_AMPLITUDE = 0.75
const KERNEL_SIZE = 0.0009
const OPACITY_BIAS = Math.log(0.1 / 0.9)
const SCALE_BIAS = inverseSoftplus(0.004)
const OFFSET_SCALE_BIAS = inverseSoftplus(0.05)
const BASE_OFFSETS = buildBaseOffsets()
function inverseSoftplus(value: number): number {
return Math.log(Math.expm1(value))
}
function softplus(value: number): number {
if (value > 20) return value
if (value < -20) return Math.exp(value)
return Math.log1p(Math.exp(value))
}
function sigmoid(value: number): number {
if (value >= 0) {
const z = Math.exp(-value)
return 1 / (1 + z)
}
const z = Math.exp(value)
return z / (1 + z)
}
function radicalInverse(base: number, value: number): number {
let result = 0
let inversePower = 1 / base
let remaining = value
while (remaining > 0) {
result += (remaining % base) * inversePower
remaining = Math.floor(remaining / base)
inversePower /= base
}
return result
}
function buildBaseOffsets(): Float32Array {
const values = new Float32Array(TRIPOSPLAT_GAUSSIANS_PER_POINT * 3)
for (let gaussian = 0; gaussian < TRIPOSPLAT_GAUSSIANS_PER_POINT; gaussian += 1) {
const samples = [
gaussian / TRIPOSPLAT_GAUSSIANS_PER_POINT,
radicalInverse(2, gaussian),
radicalInverse(3, gaussian),
]
for (let axis = 0; axis < 3; axis += 1) {
values[gaussian * 3 + axis] = Math.atanh((samples[axis] * 2 - 1) / 1.5)
}
}
return values
}
/** Apply the official ElasticGaussianFixedlenDecoder representation semantics. */
export function decodeTripoSplatGaussianFeatures(
points: Float32Array,
features: Float32Array,
): GaussianAttributes {
if (points.length % 3 !== 0) throw new Error('TripoSplat points must contain xyz triplets.')
const pointCount = points.length / 3
if (features.length !== pointCount * TRIPOSPLAT_GS_FEATURE_WIDTH) {
throw new Error(
`TripoSplat GS feature length ${features.length} does not match ${pointCount}x${TRIPOSPLAT_GS_FEATURE_WIDTH}.`,
)
}
const count = pointCount * TRIPOSPLAT_GAUSSIANS_PER_POINT
const positions = new Float32Array(count * 3)
const scales = new Float32Array(count * 3)
const rotations = new Float32Array(count * 4)
const sh0 = new Float32Array(count * 3)
const opacities = new Float32Array(count)
for (let point = 0; point < pointCount; point += 1) {
const featureBase = point * TRIPOSPLAT_GS_FEATURE_WIDTH
for (let gaussian = 0; gaussian < TRIPOSPLAT_GAUSSIANS_PER_POINT; gaussian += 1) {
const outputIndex = point * TRIPOSPLAT_GAUSSIANS_PER_POINT + gaussian
const output3 = outputIndex * 3
const output4 = outputIndex * 4
const learnedOffsetScale = softplus(features[featureBase + OFFSET_SCALE_START + gaussian] + OFFSET_SCALE_BIAS)
for (let axis = 0; axis < 3; axis += 1) {
const component = gaussian * 3 + axis
const offset =
Math.tanh(features[featureBase + XYZ_START + component] + BASE_OFFSETS[component]) *
OFFSET_AMPLITUDE *
learnedOffsetScale
positions[output3 + axis] = points[point * 3 + axis] + offset - 0.5
sh0[output3 + axis] = features[featureBase + DC_START + component]
const positiveScale = softplus(features[featureBase + SCALING_START + component] + SCALE_BIAS)
scales[output3 + axis] = Math.sqrt(positiveScale * positiveScale + KERNEL_SIZE * KERNEL_SIZE)
}
for (let component = 0; component < 4; component += 1) {
rotations[output4 + component] =
features[featureBase + ROTATION_START + gaussian * 4 + component] * 0.1 + (component === 0 ? 1 : 0)
}
opacities[outputIndex] = sigmoid(features[featureBase + OPACITY_START + gaussian] + OPACITY_BIAS)
}
}
return { positions, scales, rotations, sh0, opacities }
}
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