I am writing an exporter for SKP. I ran into a very weird problem that I could not find the correct texture coordinates for particular component instances in the model. One of such model is attached here.
The extracted texture coordinates of center part of the 4 wheels are all wrong using SUMeshHelperGetFront(Back)STQCoords even if I divide the output ST by Q and then multiply them with the scale of the texture.
I checked them in the Sketchup and found textures of the wheel are set to projected. Is there special arithmetic calculation I need to do myself after I have STQ? Please advise. Thanks a lot.
The sketchup file
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A closeup view in sketchup pro 2015 and the problematic UV extracted and rendered in my own renderer.