Multi Displacement Setup in Slim

Well, not exactly multi cos I have not done any setup for more than two displacement maps. Usually two displacement maps are enough for me, for now.

The setup is simply by adding map1 to map2 and reduce the final value by 0.5 again. Here's the image best explain what I did.

Linearizing your textures

Since we will be using linear workflow, we need to make sure the textures we used be linearized as well. To do this under TextureAtlas node, or any Image Map nodes inside Slim, simply make sure Linearize check box is set to ON. You can find this check box under Color Balance.

Without Linearize ON, the textures simply look wash out. If you are using Mari to create the textures you could add an adjustment layer sRGB2Linear to pre-linearize  the textures. That way you wouldn't have to worry about linearizing the textures inside Slim.

sRGB to Linear sRGB

If you compare the renders between Maya Render View and IT, you will see that Maya Render View has a darker output and that is because Maya Render View is using sRGB as default Image Color Profile. IT is using Linear as the default output.

To make Maya Render View to match the look of IT, you will need to change its color profile to using Linear sRGB.

Run the following MEL script to set the Color Profile to Linear sRGB:

setAttr "defaultViewColorManager.imageColorProfile" 2;

Run the following MEL script to set the Color Profile back to sRGB:

setAttr "defaultViewColorManager.imageColorProfile" 3;

Maya Render View

Displacement and Trace Bias settings

Getting the displacement to show up correctly using GPSurface with Slim network, you will need to set trace displacement to ON. However, this is not done via adding Renderman Attributes to the shape nodes. Instead, it is set via the Material Ensemble node in Slim. Under Attributes -> Ray Tracing, set Trace Displacements to ON.

One other thing to note here is the Trace Bias (Just under Trace Displacements). It is set at 0.0000 by default, meaning it will use the global value (default at 0.001) found under Render Settings -> Features -> Ray Tracing -> Trace Bias: 0.001. This value may not be what you want as you can see from the renders below. There are few ways you can change the value. The simplest way is to set the global value but this will cause all the geometry to use the same value. I prefer to set it via the Material Ensemble node, so it only applies to any geometry under attached to this material.

Another way is to simply add "Trace Bias" Renderman attributes directly to the geometry shape node. You could also make changes to the Shadow Bias attribute under the Light node but that would be like changing the global Trace Bias value which I am not too sure if that is a good idea.

8 bit to 16 bit Render buffer

Rendering with IT with turn out to be very grainy. IT output images in linear. Maya render view default is sRGB. Thus the Maya Render View will look darker with the same render and that might help hiding the grains. I have not fully tested it in Maya render view but I am guessing the grains are still there if you gamma up the render image.



To solve the problem you will need to change the render output from 8bit to 16bit or even higher 32bit. I find it 16bit is good enough. You might have to restart Maya for this settings to take effects.




Current Frame Render Option

PRMan Notes

Have been playing with Renderman for quite some time both at works and personal projects. Just wanna to start blogging down all the findings cos I am getting a little forgetful with the solutions I found....

So here we go