In order for Houdini to be able to find all the necessary RenderMan tools, first you will need to set a few environment variables:

• ensure the RMANTREE is set to the installed version of RenderMan, for example:

  export RMANTREE=/opt/pixar/RenderManProServer-21.0
  

• ensure the search path includes the bin subdirectory of RenderMan, for example:

  export PATH=$PATH:$RMANTREE/bin
  

• set the HOUDINI_DEFAULT_RIB_RENDERER to the desired version, for example:

  export HOUDINI_DEFAULT_RIB_RENDERER=prman21.0
  

After setting up these three environment variables, Houdini should be able to use RenderMan.

Each RIB target renderer has its own executable, way of compiling shaders, attributes, options, and features. Much of this is handled by Houdini behind the scenes. However, as a big head start, you can give Houdini a hint as to which render you are using by setting the environment variable HOUDINI_DEFAULT_RIB_RENDERER to the render target you want to use. The list of renderers can be inferred by looking at the $HH/RIBtargets and also at $HH/soho directory and scanning the files. The current renderers include prman21.0.

Houdini uses this variable in several places. In the hrmanshader script (a wrapper around the shader compiler), the variable controls which compiler program to call. It also controls which properties appear on the RIB output driver.

# set up for prman21.0
export HOUDINI_DEFAULT_RIB_RENDERER=prman21.0

RenderMan version 20.2 and up ships with a Houdini display driver, so there is no need for any additional setup, beyond specifying houdini in the ROP node’s Display Device parameter. Once this is done, the RIB renderer will render directly to MPlay.

It is also possible to reconfigure RenderMan to remap framebuffer device to Houdini display driver, so that all framebuffer rendering goes to MPlay as well. This can be done in rendermn.ini with this line:

/displaytype/framebuffer houdini

The render menu in viewports has an entry View:RenderMan. This will render the scene without having to create an output driver. However, Houdini needs to know which application to invoke to render the scene. This is determined by setting the environment variable HOUDINI_VIEW_RMAN.

Houdini will set the path to the default path each renderer expects. You can override the shader path in two ways:

1. Set the path by adding the rendering parameter to the output driver (preferred method).

2. Set the environment variable HOUDINI_RI_SHADERPATH.

If you customize the path, you should include $HFS/ri_shaders in the path for light shaders. If you don’t customize the path, Houdini will look for directories named ri_shaders in the HOUDINI_PATH.

For RIS shader plugins there is a HOUDINI_RI_RIXPLUGINPATH environment variable. But you don’t need to include $HFS/ri_shaders in your customization, since Houdini does not look for directories named ri_shaders because Houdini does not ship with any custom RIS shader plugins. Thus the implicit default of $RMANTREE/lib/RIS usually suffices.

If you are using RenderMan as a primary renderer, you may not want to see all of the mantra parameters in your geometry objects. You can customize the geometry object to create objects with RenderManparameters instead.

You can use VOPs to create RSL shaders, or you can import other shaders that you have written. Importing is done by creating Houdini Digital Assets that correspond to the written shaders.

To import shaders, run a Python script which parse the output of sloinfo (prman), aqsltell (Aqsis), sdrinfo (Pixie), etc. Houdini ships with 2 scripts: slo2otl.py to convert prman shaders.

The scripts are reliant on being able to parse information about shader parameters, but should be fairly easy to customize for an unsupported renderer. The script tries to implicitly guess the HDA table type and is geared for RIS shaders which are VOPs, so light and displacement .slo files implicitly yeld a VOP HDA. You can force the HDA SHOP with the -t command-line switch.

For example:

slo2otl.py -t Shop -l myshaders.hda *.slo

This will create an HDA which can be loaded into Houdini. All of the recognized shaders will exist as SHOP nodes.

hython sdl2otl.py -l myrmanshaders.otl *.sdl

In addition to importing external .slo shaders described above, Houdini allows to build shaders using VOP networks such as RSL Material. You can assign RSL Material to objects by setting the Material parameter, or to individual primitives using the Material SOP, as described in the shading documentation.

To use RenderMan’s RIS rendering mode, turn on the RIS Mode parameter in the RIS sub-tab of the Properties tab on the RenderMan node. You can then optionally specify an integrator shader in the Integrator parameter. Please see RIS shaders for more information.