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Tommy L

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Hi guys, Im new to Mental Ray as a production tool. Must say, its a darn sight better than i remember (now using Max 2008).

I have never used dislacement in MR. I have used it in VRAY and I remember how steep the learning curve was on that, so I thought Id seek a couplwe of pointers before I got started.

I need to do grass in a fairly large scene. Its for a still, so long render time and multi-pass are options that I can explore.


Using quad-core with 2g ram on xp64.


Any ideas on where to start?


Thanks in advance,


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Its taken me a while to get mrDisplacement grass that im happy with.


for the material i dont use A&D. It seems that when using A&D the grass reflects too much light and is too white.


I use a mental ray shader with DGS material in the diffuse. Set the colour boxes to black all the way and shiny down to 0. In the difuse slot (DGS) i have a mix map between two grass textures. Just to mix up the colour a bit. Grass has a lot of colour variation over larger areas in reality so this helps IMO.


For the displacement channel i just set the values to about +4.5cm for maximum and 0 for minimum. I have a grass displacement map mixed with a large noise map so the lengths are a bit more random over a large area.


Then in shadows and displacement rollout i have everything ticked. Play around with the settings. Depending on how dense your ground mesh is you will have to bump up the subdivisions. My edge length is at about .15 because i also have a corrugated roof with artefacts with a low edge length setting.


One more thing is take make sure you set the max displacement length value to just above your longest displacement in the scene is otherwise you'll be wasting memory...

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