You're just getting to grips with Houdini when someone sugguests you look at using Renderman. Perhaps you just want to speed up rendering, or maybe you've got some shaders that you want to use. In my case I was specifically interested in RenderMan before I even touched Houdini, but getting the two packages working together for the first time is far harder than you might expect.
As I've explained elsewhere RenderMan is an interface, and not a particular renderer. In principle it's therefore possible to to use BRMT, the ART Renderdrive or any other compatable renderer. However these currently require even more hoops to be jumped through, so we're going to only consider Pixars implementation - "PRMan". 9 times out of 10, when someone says RenderMan they mean PRMan, so lets start talking about PRMan with Houdini...
Firstly speed - PRMan is fast. Just for quick tests, prman is about twice the speed of Mantra, and for industrial grade rendering its just about the only choice. It's also
set path = ($path /usr/local/prman/bin /usr/local/rat/bin)
Once you've done that, save the file, and open a new shell window (by the way - I'm assuming youre on a Unix box with a C-shell here). If you type "render" and you don't get the message "command not found" then you're in buisiness.
You've also set up the path for "alfred" - more of that later. You may not have alfred, as its part of Renderman Artist Tools (rat) which are really aimed at Maya, but if its available you can use it from Houdini for network rendering. Type "alfred" to see if it works...
Following the excitment of your first PRMan render, you'll probably find that the image is a little dull. Thats because by default Houdini assigns the "plastic" shader to all objects. The first step in getting something which looks decent is to select the shading tab of each object in the object editor, and set its surface shader to be empty.
Having done this, if you render again, you should find that your Materials created in Houdini have been applied in PRMan. This is handy, as it allows you to use the Materials editor to produce basic textures while having the power of renderman shaders available if you need them.
You're now well on the way to being able to drive renderman from Houdini, but there's one trick you still need to learn - how to load new shaders into Houdini. Unfortunatly this is not as easy as you might hope, and requires two stages - one using the shell, and the other using the (dreaded) textport.
Firstly we need to tell Houdini about the shader, by creating a dialouge panel for it. This is done using the command
/usr/hfs/bin/rmands (RenderMAN Dialouge Script). The required parameters to this are somewhat complex, but fortunatly if you simply run it, it gives an example which is almost exactly as required. cd to the directory containding your shaders, and run the commend given in the example, minus the *.via on the end (as you probably don't have any of these). To make things a little more complex for beginners, the first time you run it you'll get an error message about not being able to create a file. That's because the directory doesn't exist. Use mkdir to create the directories its refering to, and try again.
If you restart Houdini you'll find that the new shaders are available in the dialouge panel, along with editors for their parameters (note that some parametes such as colour still come from the material editor, so you'll still need to create Materials as place holders).
You can now attatch the shaders, but when you try and render you'll find that they cannot be found by PRMan (check the window you started Houdini from for error messages). To tell PRMan where to find your shaders you need to open a text port and enter the following:
set RMAN_SHADERPATH = "$Job/Shaders:\
This can be entered all on one line, by removing the backslashes. You should then be able to render using the shaders from your home directory. You can also set this in the output driver in later versions of Houdini.
NCCA, Bournemouth University