The document describes the Marching Cubes algorithm, which was developed in 1987 to construct 3D models from medical imaging data like CT scans. It works by dividing the volume into cubes and using the pixel values at the cube vertices to determine triangles that approximate the surface. There are 256 possible cases but they can be reduced to 14 basic patterns. The algorithm calculates surface normals to improve image quality and has been used to generate 3D models from various medical imaging modalities.