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Account for scaling in AdjustOffsetForRotationCenter #16199

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Feb 19, 2025
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Account for scaling in AdjustOffsetForRotationCenter #16199

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22 changes: 13 additions & 9 deletions packages/dev/serializers/src/glTF/2.0/Extensions/KHR_texture_transform.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -8,15 +8,16 @@ const NAME = "KHR_texture_transform";

/**
* Computes the adjusted offset for a rotation centered about the origin.
* This does not work when scaling is involved; investigation is needed.
* @internal
*/
function AdjustOffsetForRotationCenter(babylonTexture: Texture): [number, number] {
const { uOffset, vOffset, uRotationCenter, vRotationCenter, wAng } = babylonTexture;
const cosAngle = Math.cos(-wAng);
const sinAngle = Math.sin(-wAng);
const deltaU = uRotationCenter * (1 - cosAngle) - vRotationCenter * sinAngle;
const deltaV = vRotationCenter * (1 - cosAngle) + uRotationCenter * sinAngle;
const { uOffset, vOffset, uRotationCenter, vRotationCenter, uScale, vScale, wAng } = babylonTexture;
const cosAngle = Math.cos(wAng);
const sinAngle = Math.sin(wAng);
const scaledURotationCenter = uRotationCenter * uScale;
const scaledVRotationCenter = vRotationCenter * vScale;
const deltaU = scaledURotationCenter * (1 - cosAngle) + scaledVRotationCenter * sinAngle;
const deltaV = scaledVRotationCenter * (1 - cosAngle) - scaledURotationCenter * sinAngle;
return [uOffset + deltaU, vOffset + deltaV];
}

Expand Down Expand Up @@ -80,11 +81,14 @@ export class KHR_texture_transform implements IGLTFExporterExtensionV2 {

if (babylonTexture.wAng !== 0) {
if (babylonTexture.uRotationCenter !== 0 || babylonTexture.vRotationCenter !== 0) {
if (babylonTexture.uScale !== 1 || babylonTexture.vScale !== 1) {
Tools.Warn(`${context}: Texture ${babylonTexture.name} with scaling and a rotation not centered at the origin cannot be exported with ${NAME}`);
// See https://github.com/mrdoob/three.js/issues/15831 for more details.
if (babylonTexture.homogeneousRotationInUVTransform && babylonTexture.uScale !== babylonTexture.vScale) {
Tools.Warn(
`${context}: Texture ${babylonTexture.name} with homogenousRotationInUVTransform, non-uniform scaling, and non-zero rotation cannot be exported with ${NAME}.`
);
return;
}
Tools.Warn(`${context}: Texture ${babylonTexture.name} with rotation not centered at the origin will be exported with an adjusted texture offset for ${NAME}.`);
Tools.Warn(`${context}: Texture ${babylonTexture.name} with non-origin rotation center will be exported using an adjusted offset with ${NAME}.`);
textureTransform.offset = AdjustOffsetForRotationCenter(babylonTexture);
}
textureTransform.rotation = -babylonTexture.wAng;
Expand Down