Displacement vs proxies: best option for grass in vray?

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  03 March 2011
Displacement vs proxies: best option for grass in vray?

EDIT: instead of creating a new thread, I thought perhaps this one could be turned into a Vray equivalent of the Mental Ray forests thread. I will curate this first post with the knowledge of people more experiened than I for the benefit of all

update of my grass as of 15/9/2011




It's basically Peter Guthrie's, adapted to Maya. I'll have a look at my material setup when I'm at the PC, but basically

- patch of PaintFx, pick whatever grass from the Visor suits. Toy with settings, you don't want it perfectly square. With a realistic scene scale, my patches are about 20x20cm/units
- Peter Guthrie's shader setup It's basically Peter Guthrie's, adapted to Maya. I'll have a look at my material setup when I'm at the PC, but basically

- patch of PaintFx, pick whatever grass from the Visor suits. Toy with settings, you don't want it perfectly square. With a realistic scene scale, my patches are about 20x20cm/units
- Peter Guthrie's shader setup peterguthrie.net/blog/2009/04/vray-grass-tutorial-part-2/
- second patch of grass but with a more yellow diffuse texture
- create>vray proxy of each of the two grass patches
- Install layoutTools 2011! (for Maya 2011/2012)
- instance proxies on a plane, details when I'm at PC
- second patch of grass but with a more yellow diffuse texture
- create>vray proxy of each of the two grass patches
- Install layoutTools 2011! (for Maya 2011/2012)
- *instance* proxies on a plane with LayoutTools. This is important to save RAM

To speed up rendering, you can set the filter on the file texture nodes in the 'translucency' slot of the vray2sidedMtl (assuming you followed Peter Guthrie's shader method) from 'quadratic' to 'none' but I lost some specularity doing this, unsure why.

Last edited by Richard7666 : 09 September 2011 at 07:43 AM.
 
  03 March 2011
Instancing (proxies) are generally the way to go. Far less memory and rendering overhead, compared to displacements.
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  03 March 2011
Agreed, depending on surface area, just paint a square patch with paintfx, convert to mesh, create proxy and you should be good to go
 
  03 March 2011
what about vrayFur?
 
  03 March 2011
The stinker about fur-based grass: it still has to calculate all kinds of data, and on a large field or grassy hill of great size, this means tons of rendering overhead. Instances use no more RAM than the single source geometry does. This is their beauty! It may take longer to render, as its doing more raytracing math, but the same amount of RAM.
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"Like stone we battle the wind... Beat down and strangle the rains..."
 
  03 March 2011
Displacement for grass in mental ray isn't really an option, you can tweak it for ages but in my humble opinon you will never get even close to the results you get in renderers like vray with a 2-click-solution. Sad but true :(

You can get fur to look good though on smaller surfaces, but I like the control you get when dealing with instanced geo or proxies.
 
  03 March 2011
Quote: The stinker about fur-based grass: it still has to calculate all kinds of data, and on a large field or grassy hill of great size, this means tons of rendering overhead. Instances use no more RAM than the single source geometry does. This is their beauty! It may take longer to render, as its doing more raytracing math, but the same amount of RAM.


Totally. My approach is to generally make a proxy from the fur, so only need to calc once. Fur is really efficent becouse it's simply a ribbon that always faces camera, so it's super fast to render.
 
  03 March 2011
Going with proxies, my next question is is there a faster way to populate a field of grass than constantly re-importing the same vrmesh patch of grass?

Duplicated proxies don't seem to render :(

EDIT: they do when duplicated as an instance though. Durrrr.

Now I just need a good scatter script

Last edited by Richard7666 : 03 March 2011 at 02:40 AM.
 
  03 March 2011
try vrayFur as a proxy, be so easy to groom your grass then.
 
  03 March 2011
Cheers, will give it a go.

Currently I'm using polygon-based proxies (converted from paintfx, exported to vrmesh); is it acceptable to apply a material to these *after* importing them into a scene as proxies? (I don't know if there's any alternative to that but it's what I'm doing).
 
  03 March 2011


Anyone have any suggestions? It looks quite good, though loses definition and starts to look a bit 'cartoon fluffy' the further away from the camera it gets...
 
  03 March 2011
Double post

sry, double post

Last edited by Kuky : 03 March 2011 at 09:46 PM. Reason: Double post
 
  03 March 2011
grass vray maya workflow

Hi,

You can have a look at this tutorial: Peter Guthrie part1 & Peter Guthrie part2. Use the same methods in Maya.

To scatter your vray proxy use the spPaint3D script. Use instances, not duplicate. It's better to have various patches of grass as sources for your proxies like in this very nice scene from HQ Plants. Also shaders are very nice in this scene.

I tried the method above and had the following result:







Higher resolution here

Regards,
Cristian

Last edited by Kuky : 03 March 2011 at 09:49 PM. Reason: correction
 
  06 June 2011
Currently looking much better, but not on that level^ :(



Last edited by Richard7666 : 06 June 2011 at 06:33 AM.
 
  06 June 2011
Richard, I think your grass looks amazing. I also like Kuky's grass which is very photorealistic, but not very eye-realistic. When I look at my lawn, I don't see hard blacks during daylight generally. Some dark areas, but nothing true black. Richard yours looks closer to what I see generally.

Are you using mental ray? What are you FG settings like in the globals, if so? These can help you find a middle ground between what you have and the harder shadows that Kuky presented... Especially point density and secondary bounces.
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