Field of grass...this is killing me.

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  02 February 2013
Field of grass...this is killing me.

I've posted in a few other forums asking if there's a 'best way' to create a large field of grass, as in a desert grass/shrubs setting, but for the life of me I get several views but no answers. I'm still fairly new to Maya and know there's a great deal I don't have a clue about, but having to do this scene with a large (1-2 miles!) view of a grassy terrain is becoming impossible with what I've tried using Paint Effects, ground textures, etc. It bogs down my poor 4gb x64 Win7 machine to the point Mental Ray won't even try to render it. Admittedly, I doubt I'm trying to do this the way you pros would know to do it, and trying it on a machine that needs more ram.

One problem is that I need to have the perspective (camera) move upwards, perhaps 20 feet or so, which means that the illusion or appearance of the grass extending for a mile toward the distant hills has to look believable as the camera moves up a bit. Nevertheless, I'd appreciate any suggestions on how best to create a large area of grassy plain. If this kind of thing is best done in something like Vue or another terrain program, I'm willing to hear that too. But I'm hoping there's a clever and convincing way to pull it off in Maya (2013).
Thanks in advance,
  02 February 2013
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  02 February 2013
Best way(s) imo.

Use rock procedural texture and mix in green grass and slightly brown grass. Tune the stone shader until you get nice looking patches (unless you are doing a gold course where brown grass is probably a no-no) - this is for the texture. It also helps cut out repeating textures.

1) Use Displacement for mid shots to close shots, not sure about MR these days but under V-Ray it's so quick to render displaced grass. Search Jeff Patton mental ray grass for a max tutorial
1a) Also one can use fur for mid to close shots, but this will kill you for large distances and RAM - so this is why we have to break it into far/mdedium and close shots.
2) Don't bother doing anything with far grass for only 4gb of RAM. Textures will do fine but maybe you want to add a fresnel effect to help out with shading or whatever.
3) For close shots, use hero grass scattered by spPaint3D script (by hand). Or Paint effects to geo and instance patches around.

The ultimate way, in future, but is for V-Ray only will be VRayPattern for Maya

with mental ray you only have Carbon Scatter if you want to spend some money on Maya, but judging by feedback of its use, probably don't go down this route.

The whole thing kind of sucks, I mean it's the year 2013 in computer graphics and it's next to impossible with vanilla maya tools to create large "consistent" areas of grass, Maya's particle instancer is crap. It works, but barely and needs a lot of scripting to get an automated workflow. Even then you'll end up with holes and patches and intersecting geo, it's crap.

Maxwell, Thea and a few others are starting to add this process in the rendering stage, not the modelling stage, hopefully this catches on in other renders in future. I hear V-Ray is implementing V-Ray fur with a solution to distance based quality of fur - so we can use fur for grass in the not too distant future.

HOpefully that helps in some way or another but the best method probably depends on each scene. Just experiment and whatever works, works
  02 February 2013
Try to pre-convert your static grass if possible (Vrmesh for Vray, mr_proxy for mental ray, RIB archive for Renderman/3Delight, etc.) and instance it everywhere. That will save you quite a lot of RAM. Especially for grass without any movements, you can get away with just 1 group and rotate it around. For grass with specific wind direction, you might need a few more variations.

Technically speaking, I think you can use spPaint to place grasses for MR too. I've never tested it with MR but I can ensure you that spPaint works with vrmesh and RIB archive

Avoid doing ambient occlusion on your grass. Even worse if your grass has transparency/cut out opacity.
  02 February 2013
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