Best way to project images onto a mesh with known camera positions

Basically I have this 3d reconstruction software I'm writing and I can currently create obj files but I want to add textures to them. The clay renders of faces is a little off putting. What is the best way to add the colour data? I have the camera images and the camera projection matrix but I'm not sure how to actually store the projection? Do I need to UV unwrap my model? Because these are high fidelity models \~ 100,000 …

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