Max Mental Ray BSP

BSP tree stands for Binary Space Partition tree.

The default BSP ray trace acceleration method is often used for small/medium Max scenes (i.e. less than one million triangles/polygons).Users often press the hotkey 7 to determine the number of polygons/faces/triangles in the scene. The default BSP ray trace acceleration method is often used for small/medium Max scenes (i.e. less than one million triangles/polygons). Users often press the hotkey 7 to determine the number of polygons/faces/triangles in the scene. It is worth noting that although the BSP parameters are under the ray tracing group, it only affects the geometry, as oppose to reflections, etc. 

This ray trace acceleration method essentially helps mental ray to cast rays in a speedy matter by creating an imaginary bounding box around the entire scene, with subdivisions. These subdivided patches/cells inside the bounding box are technically designated as voxels.Mental ray usually splits all voxels of the scene in three axes (i.e. X; Y; Z); in almost equal number of triangles, until depth is reached.

The "Size" and "Depth" parameters help mental ray to determine the total number of triangles (i.e.leafs)to be processed for ray casting/testing. The higher the depth values, the fewer the voxels will be. Fewer voxels equals faster rendering times, as mental ray will use fewer voxels to test the rays against.The default Size value of 10 sets the minimum number of objects to be found in the scene before a voxel is split (in all three axes (i.e. X; Y; Z). Smaller values equates to more voxels and slower rendering times.

When shooting a ray there are 2 phases

a) whilst checking/hitting voxels, it will touch triangles (i.e. leafs) in the process. If perchance there are 1000 triangles (i.e. leafs) in a voxel; each will be tested 40 times (i.e. default depth value). Subsequently the rendering times will be slow. If there are only 10 triangles (i.e. leafs), the process will be faster.With this in mind, the user’s goal should be to reduce the number of average and maximum leafs in the BSP tree.The total rendering time is a combination of the time it takes to create the voxels, move down the tree depth (i.e. pre processing/translation); and the final time to check/split the triangles (i.e. leafs) during the rendering time.

b) Moving down the BSP tree depth whilst checking/hitting all axis of each voxel. To have a visual representation of the BSP process, simply go to the mental ray processing parameters rollout. Under "diagnostics" parameters, enable the “visual” group:

This visual group consists of the following:

1-Sampling rate

2-coordinate space

3-Photon

4-BSP

5-Final Gather

The BSP visual diagnostics is divided by three different colors: Blue, Green and Red.Blue areas represent the lower areas of subdivision (i.e. less computation)
Green areas represent the middle areas of subdivision (i.e. intermediate computation)
Red areas represent greater areas of subdivision (i.e. high computation).

Production companies prefer to have a mix of all three colors in their diagnostics; which is an indication that mental ray is efficiently choosing the areas of the geometry to subdivide and otherwise. To fine-tune the BSP values, simply use a nice/simple texture or colour in "material override" toggle at a small resolution (i.e. 500x500 pixels).
The "material override" function has been covered in detail

Deflectors

Deflectors are used to deflect particles or to affect dynamics systems.

          

Topics in this section

POmniFlect Space Warp

POmniFlect is a planar version of the omniflector type of space warp. It provides enhanced functionality over that found in the original Deflector space warp, including refraction and spawning capabilities.

PDynaFlect Space Warp

PDynaFlect (planar dynamics deflector) is a planar version of the dynaflector, a special class of space warp that lets particles affect objects in a dynamics situation. For example, if you want a stream of particles to strike an object and knock it over, like the stream from a firehose striking a stack of boxes, use a dynaflector.

SOmniFlect Space Warp

SOmniFlect is the spherical version of the omniflector type of space warp. It provides more options than the original SDeflector. Most settings are the same as those in POmniFlect. The difference is that this space warp provides a spherical deflection surface rather than the planar surface. The only settings that are different are in the Display Icon area, in which you set the Radius, instead of the Width and Height.

SDynaFlect Space Warp

The SDynaFlect space warp is a spherical dynaflector. It’s like the PDynaFlect warp, except that it’s spherical, and its Display Icon spinner specifies the icon's Radius value.

UOmniFlect Space Warp

UOmniFlect, the universal omniflector, provides more options than the original UDeflector. This space warp lets you use any other geometric object as a particle deflector. The deflections are face accurate, so the geometry can be static, animated, or even morphing or otherwise deforming over time.  

UDynaFlect Space Warp

The UDynaFlect space warp is a universal dynaflector that lets you use the surface of any object as both the particles deflector and the surface that reacts dynamically to the particle impact.

SDeflector Space Warp

The SDeflector space warp serves as a spherical deflector of particles.

UDeflector Space Warp

The UDeflector is a universal deflector hat lets you use any object as a particle deflector.

Space Warp

The Deflector space warp acts as a planar shield to repel the particles generated by a particle system. For example, you can use Deflector to simulate pavement being struck by rain. You can combine a Deflector space warp with a Gravity space warp to produce waterfall and fountain effects………