Before we get into talking about light estimation for AR, let's step back and review the rendering process of a 3D model. Take a look at the following diagram that explains the rendering process at a high level:
Typical rendering process for a 3D model
Now, the diagram only visually demonstrates the rendering process. Geometry and vertex shaders never actually render a wireframe model. Rather, they only position and color vertices and surfaces, which are then fed into the pixel/fragment and lighting shaders. This last step is called rasterization and represents the final step when the 2D image is generated or rasterized.
The rendering process we are talking about here is for standard real-time rendering on a device's GPU using DirectX or OpenGL. Keep in mind that there are other rendering processes used for real-time (voxel) and non real-time (ray...
