RMS 18
Occlusion AOV

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Related Topic

    RMS: Occlusion
    RenderMan: AOV's

Introduction

This tutorial demonstrates the use of the RMSGILight to output occlusion as a secondary image or AOV (arbitrary output variable). Figures 1 and 2 show a simple scene rendered as a primary beauty pass and a secondary AOV occlusion pass. Notice the occlusion AOV is not inverted but this can easily be done in a compositing application such as Nuke.

Figure 1 - Beauty Pass

Figure 2 - occlusion AOV

Note the RMSGILight (global illumination light) is not a regular light source because its xyz position in a scene is of no consequence. Instead of calculating direct lighting it uses a RSL Shading Language (RSL) function called indirectdiffuse() to calculate,
    - color bleeding, aka global illumination, and
    - occlusion, the extend to which a surface is "masked" by other surfaces.

Step 1 - Adding a Global Illumination "Light"

From the RenderMan->RMS Lights menu choose "RMS GI Light". A sphere will appear in the scene. It can be moved to any convenient location. Change the samples to 512 or higher for smoother occlusion - figure 2.

Figure 3

Step 2 - Adding an AOV

2.1     Open the RenderMan Controls Window by clicking the shelf icon.

     

2.2     From the View menu choose "Pass Settings Tree".
2.3     Select "perspShape_Final", then select the "Outputs" tab.
2.4     Click on "Add Channels/Outputs".
2.5     Right-mouse click float occlusion, choose "Create Output from Channel".
     

Render the scene and in "it" Catalog click the triangle to preview the AOV.

     

If additional AOVs are added ensure the RenderMan Controls output panel is set to OpenEXR.