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# MayaMan Tutorial: Occlusion/Radiance Baking With PRMan

This tutorial explains how to compute occlusion/radiance data and then reuse it on subsequent renders.

- In the basic options panel, select 'Pixar - prman 12.5 bake' as the renderer, this will instruct MayaMan to tell PRMan not to cull hidden surfaces, etc.
- In the global illumination panel, turn on radiance/bleed and quality dials as desired.
- In the global illumination panel, enter a 'save file' name that will be accessible by future renders (ie: a network location), a value like `T:/film/showname/assets/occlusion/sc29.bkm` is good
- Do a preview, this will create a point cloud file that will be automatically converted to a brickmap at the location indicated by the save file entered in the previous step, if the camera is going to move through the scene then this preview should happen from a camera that frames all the areas to be viewed
- Switch the renderer back to 'Pixar - prman 12.5'
- Move the value from the 'save file' field to the 'seed file' field
- Preview, this time the render will happen much quicker, it will use the data from the brickmap instead of computing it with ray tracing
- Note, if the result is blocky, rebake with slower maxerror/maxpixeldist.

### BrickMap or PTC?

If the supplied 'save file' name ends in .ptc then the result will be a point cloud file, when prman uses a point cloud file during re-rendering it has to load the whole cloud into memory at once. Rendering to a pointcloud file is handy if you want to play with the brickmap conversion to select an optimal balance between size and quality. Render to a pointcloud file is also useful if you need to bake from several different views... the pointclouds can be merged into a single brickmap (or pointcloud), this mode of operation is left to the user.

If the supplied file name ends in .bkm then the point cloud file will be written to temporary storage and then brickmake will be used to convert the point cloud file to a brickmap. The maxerror value passed to the brickmake phase is 10% of the maxerror value used during the occlusion computation.

### Advanced Baking Strategies

For large scenes where per-model or per-material baking is to be used, instead of doing a preview to create the brickmap set up for rib-gen only, then invoke "MayaManRender -cvi x" where x is 1 for per-material, or 2 for per-model. This will create a sequence of ribs (all at the current frame) that turns on camera visibility for only one material/model at a time.. this provides a way of distributing a bake across a large number of machines.

### Tips

Doing per-model or per-material baking is recommended. Instead of one big file it creates smaller files which may avoid memory problems during brickmap conversion, it also provides the opportunity to increase the quality of of problem objects without having to rebake the whole scene at higher quality. To selectively rebake parts of the scene, make all of the objects you are happy with invisble to the camera, they will still exist in the scene for the purposes of gathering the occlusion data but as they are not visible to the camera they will not be recomputed.

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