The reseach about the BSP of Mental Ray
Some friends told me that mental ray is so slow especially the scene with a huge number polygons or the issue about the stability of mentalray rendering a big file. Probability we can reduce the parameters; for instance FinalGather, GI, Sample pixel or even resolution. However, we can also use BSP to control the rendering time or memory cost to avoid quality loss in the previous way.
So, The first thing we should know is what the BSP is? Basically, This feature you can comprehend as cutting the 3d space to many big or small bucket that has same polygons for save memory or accelerate rendering speed. Let`s take a look at this image if you still have no idea about what am i said. Here is scene with a hign poly car and ground, as you can see at the area marked num 1 almost nothing there, so BSP tree assinged a bigger bucket for this area, and the smallest bucket is the yellow area which has much detail there. In this way, Mentalray is able to use memory as efficiently as possible.
The official defined of BSP is:
The BSP (binary space partitioning) acceleration method recursively subdivides 3D space into a nested set of voxels, small boxes with triangles in them. It is efficient, but careful attention should be given to the size and depth parameters, which can have a large impact on speed and memory usage.
Size ... (全文...)