diff --git a/code/glTF2/glTF2Importer.cpp b/code/glTF2/glTF2Importer.cpp index 88345f98a..dd80aeba9 100644 --- a/code/glTF2/glTF2Importer.cpp +++ b/code/glTF2/glTF2Importer.cpp @@ -204,11 +204,21 @@ inline void SetMaterialTextureProperty(std::vector &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. + const ai_real rcos(cos(-transform.mRotation)); + const 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); }