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[pull] dev from mrdoob:dev #1563

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Merged
pull merged 1 commit into from
Aug 12, 2026
Merged

[pull] dev from mrdoob:dev #1563

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77 changes: 25 additions & 52 deletions examples/jsm/utils/GaussianSplatUtils.js
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Original file line number Diff line number Diff line change
@@ -1,6 +1,10 @@
import {
BufferAttribute,
BufferGeometry
BufferGeometry,
Matrix3,
Matrix4,
Quaternion,
Vector3
} from 'three';

const SH_C0 = 0.2820947917738781;
Expand All @@ -15,6 +19,13 @@ const GAUSSIAN_SPLAT_PLY_PROPERTY_MAPPING = {
opacity: [ 'opacity' ]
};

const _covarianceMatrix = new Matrix3();
const _covarianceMatrixTranspose = new Matrix3();
const _rotationScaleMatrix = new Matrix4();
const _quaternion = new Quaternion();
const _scale = new Vector3();
const _zero = new Vector3();

function sigmoid( value ) {

return 1 / ( 1 + Math.exp( - value ) );
Expand Down Expand Up @@ -59,60 +70,22 @@ function writeColorBytesFromSH0( target, offset, r, g, b, a ) {

function writeCovariance( target, offset, sx, sy, sz, qx, qy, qz, qw ) {

// Math.sqrt is significantly faster than Math.hypot, and the overflow
// protection of Math.hypot is unnecessary for quaternion components.
const length = Math.sqrt( qx * qx + qy * qy + qz * qz + qw * qw );

if ( length === 0 ) {

qx = 0;
qy = 0;
qz = 0;
qw = 1;
_quaternion.set( qx, qy, qz, qw ).normalize();
_scale.set( sx, sy, sz );
_rotationScaleMatrix.compose( _zero, _quaternion, _scale );

} else {
_covarianceMatrix.setFromMatrix4( _rotationScaleMatrix );
_covarianceMatrixTranspose.copy( _covarianceMatrix ).transpose();
_covarianceMatrix.multiply( _covarianceMatrixTranspose );

const invLength = 1 / length;
qx *= invLength;
qy *= invLength;
qz *= invLength;
qw *= invLength;

}
const elements = _covarianceMatrix.elements;

const x2 = qx + qx;
const y2 = qy + qy;
const z2 = qz + qz;
const xx = qx * x2;
const xy = qx * y2;
const xz = qx * z2;
const yy = qy * y2;
const yz = qy * z2;
const zz = qz * z2;
const wx = qw * x2;
const wy = qw * y2;
const wz = qw * z2;

const r00 = 1 - ( yy + zz );
const r01 = xy - wz;
const r02 = xz + wy;
const r10 = xy + wz;
const r11 = 1 - ( xx + zz );
const r12 = yz - wx;
const r20 = xz - wy;
const r21 = yz + wx;
const r22 = 1 - ( xx + yy );

const sxx = sx * sx;
const syy = sy * sy;
const szz = sz * sz;

target[ offset ] = r00 * r00 * sxx + r01 * r01 * syy + r02 * r02 * szz;
target[ offset + 1 ] = r00 * r10 * sxx + r01 * r11 * syy + r02 * r12 * szz;
target[ offset + 2 ] = r00 * r20 * sxx + r01 * r21 * syy + r02 * r22 * szz;
target[ offset + 3 ] = r10 * r10 * sxx + r11 * r11 * syy + r12 * r12 * szz;
target[ offset + 4 ] = r10 * r20 * sxx + r11 * r21 * syy + r12 * r22 * szz;
target[ offset + 5 ] = r20 * r20 * sxx + r21 * r21 * syy + r22 * r22 * szz;
target[ offset ] = elements[ 0 ];
target[ offset + 1 ] = elements[ 3 ];
target[ offset + 2 ] = elements[ 6 ];
target[ offset + 3 ] = elements[ 4 ];
target[ offset + 4 ] = elements[ 7 ];
target[ offset + 5 ] = elements[ 8 ];

}

Expand Down