The document discusses several methods for visible surface detection or hidden surface removal in 3D computer graphics, including object space and image space methods. Object space methods determine visibility in 3D coordinates and include depth sorting and binary space partitioning (BSP) trees, while image space methods determine visibility on a per-pixel basis and include the depth-buffer or z-buffer method and ray casting. The depth-buffer method uses two buffers, a frame buffer and depth buffer, to render surfaces from back to front on a pixel-by-pixel basis. BSP trees recursively subdivide space with splitting planes to give a rendering order that correctly draws objects from back to front.