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Add more control on GS view update threshold #17638

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Merged
sebavan merged 3 commits into from
Jan 26, 2026
+23 −18
Merged

Add more control on GS view update threshold #17638

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b5637fb
Add more control on GS view update threshold
CedricGuillemet Jan 9, 2026
233fc88
Merge branch 'master' of https://github.com/BabylonJS/Babylon.js into…
CedricGuillemet Jan 26, 2026
122d32e
use projection matrix
CedricGuillemet Jan 26, 2026
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41 changes: 23 additions & 18 deletions packages/dev/core/src/Meshes/GaussianSplatting/gaussianSplattingMesh.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -297,7 +297,7 @@ export interface PLYHeader {
export class GaussianSplattingMesh extends Mesh {
private _vertexCount = 0;
private _worker: Nullable<Worker> = null;
private _modelViewMatrix = Matrix.Identity();
private _modelViewProjectionMatrix = Matrix.Identity();
private _depthMix: BigInt64Array;
private _canPostToWorker = true;
private _readyToDisplay = false;
Expand Down Expand Up @@ -330,6 +330,13 @@ export class GaussianSplattingMesh extends Mesh {
private static readonly _BatchSize = 16; // 16 splats per instance
private _cameraViewInfos = new Map<number, ICameraViewInfo>();

private static readonly _DefaultViewUpdateThreshold = 1e-4;

/**
* Cosine value of the angle threshold to update view dependent splat sorting. Default is 0.0001.
*/
public viewUpdateThreshold: number = GaussianSplattingMesh._DefaultViewUpdateThreshold;

protected _disableDepthSort = false;
/**
* If true, disables depth sorting of the splats (default: false)
Expand Down Expand Up @@ -559,12 +566,15 @@ export class GaussianSplattingMesh extends Mesh {
}

public _getCameraDirection(camera: Camera): Vector3 {
const cameraMatrix = camera.getViewMatrix();
this.getWorldMatrix().multiplyToRef(cameraMatrix, this._modelViewMatrix);
const cameraViewMatrix = camera.getViewMatrix();
const cameraProjectionMatrix = camera.getProjectionMatrix();
const cameraViewProjectionMatrix = TmpVectors.Matrix[0];
cameraViewMatrix.multiplyToRef(cameraProjectionMatrix, cameraViewProjectionMatrix);
this.getWorldMatrix().multiplyToRef(cameraViewProjectionMatrix, this._modelViewProjectionMatrix);

// return vector used to compute distance to camera
const localDirection = TmpVectors.Vector3[1];
localDirection.set(this._modelViewMatrix.m[2], this._modelViewMatrix.m[6], this._modelViewMatrix.m[10]);
localDirection.set(this._modelViewProjectionMatrix.m[8], this._modelViewProjectionMatrix.m[9], this._modelViewProjectionMatrix.m[10]);
localDirection.normalize();

return localDirection;
Expand Down Expand Up @@ -627,22 +637,21 @@ export class GaussianSplattingMesh extends Mesh {

const previousCameraDirection = cameraViewInfos.cameraDirection;
const dot = Vector3.Dot(cameraDirection, previousCameraDirection);
if ((forced || Math.abs(dot - 1) >= 0.01) && this._canPostToWorker) {
if ((forced || Math.abs(dot - 1) >= this.viewUpdateThreshold) && this._canPostToWorker) {
cameraViewInfos.cameraDirection.copyFrom(cameraDirection);
cameraViewInfos.frameIdLastUpdate = frameId;
this._canPostToWorker = false;
if (this._worker) {
this._worker!.postMessage(
{
view: this._modelViewMatrix.m,
modelViewProjection: this._modelViewProjectionMatrix.m,
depthMix: this._depthMix,
useRightHandedSystem: this._scene.useRightHandedSystem,
cameraId: camera.uniqueId,
},
[this._depthMix.buffer]
);
} else if (_native && _native.sortSplats) {
_native.sortSplats(this._modelViewMatrix, this._splatPositions!, this._splatIndex!, this._scene.useRightHandedSystem);
_native.sortSplats(this._modelViewProjectionMatrix, this._splatPositions!, this._splatIndex!, this._scene.useRightHandedSystem);
if (cameraViewInfos.splatIndexBufferSet) {
cameraViewInfos.mesh.thinInstanceBufferUpdated("splatIndex");
} else {
Expand Down Expand Up @@ -1446,7 +1455,7 @@ export class GaussianSplattingMesh extends Mesh {
newGS.makeGeometryUnique();
newGS._vertexCount = this._vertexCount;
newGS._copyTextures(this);
newGS._modelViewMatrix = Matrix.Identity();
newGS._modelViewProjectionMatrix = Matrix.Identity();
newGS._splatPositions = this._splatPositions;
newGS._readyToDisplay = false;
newGS._disableDepthSort = this._disableDepthSort;
Expand Down Expand Up @@ -1474,12 +1483,12 @@ export class GaussianSplattingMesh extends Mesh {
// udpate on view changed
else {
const cameraId = e.data.cameraId;
const viewProj = e.data.view;
const modelViewProjection = e.data.modelViewProjection;

const vertexCountPadded = (positions.length / 4 + 15) & ~0xf;
if (!positions || !viewProj) {
if (!positions || !modelViewProjection) {
// Sanity check, it shouldn't happen!
throw new Error("positions or view is not defined!");
throw new Error("positions or modelViewProjection matrix is not defined!");
}

depthMix = e.data.depthMix;
Expand All @@ -1491,13 +1500,9 @@ export class GaussianSplattingMesh extends Mesh {
indices[2 * j] = j;
}

let depthFactor = -1;
if (e.data.useRightHandedSystem) {
depthFactor = 1;
}

for (let j = 0; j < vertexCountPadded; j++) {
floatMix[2 * j + 1] = 10000 + (viewProj[2] * positions[4 * j + 0] + viewProj[6] * positions[4 * j + 1] + viewProj[10] * positions[4 * j + 2]) * depthFactor;
floatMix[2 * j + 1] =
10000 - (modelViewProjection[2] * positions[4 * j + 0] + modelViewProjection[6] * positions[4 * j + 1] + modelViewProjection[10] * positions[4 * j + 2]);
}

depthMix.sort();
Expand Down
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