View Full Version : facevarying variable in Renderman`

07 July 2005, 07:02 PM
Can someone explain to me what the facevarying variable does in Renderman and where to find info about it in the pixar docs? I'm having trouble finding anything bout it other than i's kind of like an array of info about the polys on an object... :banghead:

07 July 2005, 06:27 AM
facevarying variables store a value per vertex of each face. Consider a polygonal cube with 8 verts and 6 faces. Then the different storage classes require the following number of values:

uniform: 6 (for each face)
varying/vertex: 8 (for each vert)
facevarying: 24 (= 6 faces * 4 verts per face)

This allows storing different values on the same vertex depending on which face we currently are (which is most useful for subdivision surfaces where you cannot simply duplicate vertices).

- Matthias -

07 July 2005, 04:41 PM
So, you could use something like this to store data on doing HDRI or occlusion or somehting, right?

07 July 2005, 03:10 AM
HDRI data is a floating point number that expresses how much light there is in the world environment. It doesn't have any clear upper bounds. Ambient occlusion is a percentage/ratio that represents how much light any given point receives. I am curious as to why you'd want to save these types of lighting data directly into a model. Could you explain?

But if you want to save it so it's quicker to re-render or useful for interactivity, why not just bake, for example, an ambient occlusion texture map?

[edits made because I hit the post button too quickly]

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07 July 2005, 03:10 AM
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