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View Full Version : how to do a nature scene / forest with maya mental ray ?


vhylynx
08-16-2005, 01:22 PM
I am interested to learn vue 5, but i also heard here that the big studios had never used it before in their production pipe line. So, how did they do a nature scene, with cg trees, landscapes and things? Since i know that they use mental ray to render amazing stuff in major blockbuster movies, can anyone tell me how to use maya mental ray to render a forest, or perhaps a mountain with lots of plants...

One of my goal is to create architectural visualizations where plants, trees and other natural phenomenons are really important to enhance believability of my work.

thank you

playmesumch00ns
08-16-2005, 01:27 PM
I'm trying to think of any blockbuster movie that contains a full 3d cg landscape.

If there needs to be a virtual landscape, chances are it'll be a matte painting.

rendermaniac
08-19-2005, 12:14 AM
Lord of the Rings 2 had a lot of CG vegetation. One of Weta's finest - Martin Preston - wrote a system to generate vegetation. He had a Siggraph sketch about it (2002 or 2003??). It sounded like a very customised solution.

The recent Stealth also had a lot of CG landscapes - Digital Domain have Matt Fairclough working for them who wrote http://www.planetside.co.uk/terragen/ - very impressive terrain software. I think their in house version must be very impressive now - the public version does not support vegetation yet.

I am sure quite a lot was matte painting too in both cases.

The quickest way to get to get vegetation quickly and reasonably painlessly is to use Maya's paintFX tools. This lets you paint on vegetation and build up complexity quite quickly. I am not sure if it renders in Mental Ray.

Simon

vhylynx
08-19-2005, 01:12 PM
Mental ray for maya 6.5 doesnt render paint fx. I just found about rpc for maya, but it doesnt work on maya 6.5, i think. I dont know what to do. Vue 5 doesnt integrate nicely with maya, too much work and tweaking around involved... or perhaps it is because i just started playing around with vue.

bahman
08-21-2005, 10:33 PM
Did U ever use Xforg4Maya ?
This tool generates realy great plants that u can also render it
in mental ray.
Link: http://www.xfrogdownloads.com/greenwebNew/news/pressStart.htm

MartinGFoster
08-22-2005, 12:21 AM
typically creating a really deep background involves about 3 distinct layers. The technique may have to be modified for different camera moves:

the matte painting in the far background. This can be made of muliple layers and use a multi-planing technique. You can add image warping and/or noise in the comp to keep the trees alive a bit.

the middle distance might be CG but mostly using "X" trees or some similar technique. This involves simple planes arranged in an "X" from a top view. Each plane has a texture of a tree and a matching opacity map. You can again add image warping and/or noise in the comp to keep the trees alive a bit. This is the cheap way to add dynamics. The RPC plugin software is a fancy version of the tex/op card trick favoured by architects but I doubt it is used in well-budgeted feature films. I used it in architectural-viz but found it substandard for visual effects. They use a library of texture maps of photographed trees and people shot on a turntable. As the camera to plane angle changes the software picks a matching image to simulate 3d. You can't get close or fly too much off horizontal axis before they fall apart and behave in some bizarre looking way.

For full 3d needs, like flying towards, through, and over vegetation, a level-of-detail (LOD) system like PRMan's LOD combined with delayed-read-archive works very well. Your modellers will have to make careful versions of the trees so that transitions through different levels don't "pop" or change profile outline too radically during the cross-dissolve between resolutions. Alternatively, a procedural plugin can generate the complexity of tree/shrub required at render time in a view-dependent fashion. I like the explicitly modelled version of doing LOD's because I find that VFX sup's like to see line-ups of different levels to make sure they approve of each one. It's also easy to debug.

To actual "plant" the forest you can usually use a particle system or crowd system to distribute the trees in a logical yet pseudo-random way. The system may also facilitate the use of dynamics for wind, or explosions, etc.

Most big studios probably use either PRMan for this kind of work OR their own renderer. I haven't heard of Mental Ray being especially used for this kind of work. At my employer (R&H) we use our own renderer, sometimes Mantra (Houdini's renderer), and very occasionally PRMan because we have limited licenses. We try to do everything custom for maximum control but for some work, especially FX, we'll use Houdini combined with custom plugins.

If you want to be a TD in a large company, using a "canned" plugin like vue5 is probably not going to do you any favours. I think if you were able to demonstrate the ability to create a forest setup in PRMan (or a compatible renderer) you'd have a decent chance of getting a job. You could use Maya or Houdini as the 3d front end to a RenderMan compatible renderer.

I am interested to learn vue 5, but i also heard here that the big studios had never used it before in their production pipe line. So, how did they do a nature scene, with cg trees, landscapes and things? Since i know that they use mental ray to render amazing stuff in major blockbuster movies, can anyone tell me how to use maya mental ray to render a forest, or perhaps a mountain with lots of plants...

One of my goal is to create architectural visualizations where plants, trees and other natural phenomenons are really important to enhance believability of my work.

thank you

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