Output Statistics

One way to study the info on the rendering would be the use of Output Statistic.

To enable this feature, go to Render Settings, under Advance tab, Statistics, check Output Statistics to turn it ON. Insert a path into Statistics XML File field:

C:/myProj/mystatistics.xml

After each render, you should get mystatistics.xml file. Drag and drop it into Firefox browser.
Look under Memory tab, search for Radiosity Cache and you can see how much memory was used in the render. Renderman default 102400 kilobytes (100mb) for Radiosity Cache. If the renders use up more than 100 mb, then it would be better to raise the default to match the memory used, else the rendering will get slowdown.

Another info to look up for is the Bounds in the xml file, This is where you will find if your displacement bound has been set too low or too high.

Other interesting stats to look out for is Texture. Here you will find how many hits are at what resolution if the textures and the memory used.

Displacement out correctly

Here's what I find a little weird between using a grayscale and RGB displacement map.

If you were to create a grayscale 50% gray 16bit TIF image. Convert into tex and used it as displacement map. Even though it is 50% gray, there is still changes to the geometry.

However, if you were to take the grayscale TIF image again, change it into 16bit RGB TIF, the geometry stay the same. That's something I have to live with at the moment.

To correctly setup displacement in Slim, here are few things to do:
- Create a float MayaImageFile node, load tex file, use Luminance RGB as Channel. Set the S and T Filtering to 0.

- Connect it to the Float Displacement handler in GPSurface. Within GPSurface node, set Displacement Encoding to Centered. Adjust Displacement Scale accordingly.

- Remember to set Displacement Bound either within GPSurface or MaterialEnsemble node. Also remember to turn ON Trace Displacement (If using Raytracing) inside Material Ensemble node.

You can also plug in a normal Bump map texture into GPSurface for very fine details....

That annoying rendering problems with the camera to use

If you are like me, having trouble to get Renderman to use the camera you want as render camera, especially rendering to IT, here's the command line to solve the problems:

rmanLoadPlugin; setCurrentRenderer renderMan; rmanChangeRendererUpdate; rmanRenderPass("Final", "yourCamShape");

Noticed that the pass used is Final. There are in fact Final and Preview pass by default. Something that you could take advantage of when doing interactive rendering.