[daenz]

It's been awhile since I've looked at the code, but take a look at the code around this https://github.com/amoffat/metabrite-receipt-tests/blob/mast... for mapping from UV space to image space

TLDR: using a KD-tree, I find the face containing the UV coordinate. Then I transform the UV coordinate to barycentric coordinates within that containing face, then put that barycentric coordinate through the local -> world -> view -> perspective transform matrices

[emcq]

A common approach in rendering engines to convert screen space coordinates to objects is to render a second image with light and shadow disabled where the color uniquely maps to an id. You then can uniquely identify 24 bits worth of objects without needing to maintain a KD tree.