ptc 与 raytrace比较

Main benefits are summarized below:

Due to the nature of the point-based approach, the resulting ambient occlusion effect is smooth.

Displacements, a costly operation in the ray-tracing case, come at no additional cost in the point-based method.

No need to declare objects visible to the ray-tracer, this can save a lot of memory.

The drawbacks of point-based occlusion can be summarized in the following points:

It is an approximation to the real occlusion. In general, the obtained occlusion is darker than the ray tracing case and it is necessary to adjust quite a few parameters to obtain the same look. More about parameter adjustments in Algorithm Control Parameters.

The pipeline is obviously more complicated since one need a special pass to create the point cloud(s).

上述摘自3delight 文档

 ao 效果更smooth

对置换支持更快更高

避免光线跟踪，减少内存使用

 

ptc ao的不足：

与光线跟踪的ao相比，ptc ao只是近似计算的非真实ao，所以某些地方可能比raytrace的药黑，需要更多的调节参数才能达到一样的效果。

因为需要预先计算出ptc文件，所以流程和操作上稍微复杂。 

 

转载于:https://www.cnblogs.com/rdRoad/archive/2009/11/01/1594204.html