chapter  5
21 Pages

Vertex Processing

ByJungHyun Han

The polygon meshes in a Three-dimensional (3D) scene are passed to the graphics processing unit (GPU) for rendering. The GPU transforms the polygons to their two-dimensional (2D) form to appear on the screen and computes the colors of the pixels comprising the 2D polygons. The pixels are written into a memory space called the color buffer. The image in the color buffer is displayed on the screen. In the GPU, rendering is done in a pipeline architecture, where the output of one stage is taken as the input for the next stage. A shader in the rendering pipeline is a synonym of a program. The out-of-frustum objects do not contribute to the final image and are usually discarded before entering the GPU pipeline. If a polygon intersects the boundary of the view frustum, it is clipped with respect to the boundary, and only the portion inside of the view frustum is processed for display.