| 摘要 |
The fundamental concept of expressing brightness level of a geometric primitive is to control the number of rendered display elements, representing desired brightness level, in the geometric primitive as a fraction of the maximum number of display elements, representing the maximum brightness level, that can be placed in it. There are two approaches to achieve this control: Point-based Rendering and Intersection-based Rendering. In Point-based Rendering, a geometric primitive is converted into a representation of sampling points and then the sampling points are rendered. In Intersection-based Rendering, the intersections of a geometric primitive with the frame slices are rendered. The basic procedure to render a texture-mapped surface is to divide the surface into a number of regions, each region having a different intensity range, and then render each region with a different density of display elements to represent different brightness level. The procedure of rendering a 3D volume with gray scale distribution is similar.
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