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Correctly change the coordinate system of the glTF UV transforms to match those used internally inside Assimp. This should now hopefully result in a complete implementation for issue #2119

pull/2787/head
Paul Arden 2019-11-27 11:05:31 +11:00
parent 81ffacfc34
commit e4f1b8e609
1 changed files with 13 additions and 3 deletions
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16
code/glTF2/glTF2Importer.cpp
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@ -204,11 +204,21 @@ inline void SetMaterialTextureProperty(std::vector<int> &embeddedTexIdxs, Asset
if (prop.textureTransformSupported) {
aiUVTransform transform;
transform.mTranslation.x = prop.TextureTransformExt_t.offset[0];
transform.mTranslation.y = prop.TextureTransformExt_t.offset[1];
transform.mRotation = prop.TextureTransformExt_t.rotation;
transform.mScaling.x = prop.TextureTransformExt_t.scale[0];
transform.mScaling.y = prop.TextureTransformExt_t.scale[1];
transform.mRotation = -prop.TextureTransformExt_t.rotation; // must be negated
// A change of coordinates is required to map glTF UV transformations into the space used by
// Assimp. In glTF all UV origins are at 0,1 (top left of texture) in Assimp space. In Assimp
// rotation occurs around the image center (0.5,0.5) where as in glTF rotation is around the
// texture origin. All three can be corrected for solely by a change of the translation since
// the transformations available are shape preserving. Note the importer already flips the V
// coordinate of the actual meshes during import.
ai_real rcos(cos(-transform.mRotation));
ai_real rsin(sin(-transform.mRotation));
transform.mTranslation.x = (0.5 * transform.mScaling.x) * (-rcos + rsin + 1) + prop.TextureTransformExt_t.offset[0];
transform.mTranslation.y = ((0.5 * transform.mScaling.y) * (rsin + rcos - 1)) + 1 - transform.mScaling.y - prop.TextureTransformExt_t.offset[1];;
mat->AddProperty(&transform, 1, _AI_MATKEY_UVTRANSFORM_BASE, texType, texSlot);
}