TextureBuilder is a node for Nuke that can gather image data from a number of frames to create a texture of an object placed in those frames. It's initially meant to work in couple with FaceBuilder, but it can work with any geometry eliminating the Project3D/FrameHold/MergeMat madness people usually go through when they need to get a texture of an object or a clean plate.
No, it works with any geometry.
When you set it to 0, each pixel color is calculated using all the projections where the pixel was facing the camera even with really narrow angles, the resulting colour of the pixel then is a total average. When you increase the number, projections whose angle is closer to 90° affect the colour more than others. If you push the slider up to the maximum — 100, only the 90° projections are used.