Some Tips: Modeling For V-Ray

TedVitale_CG · 13 Jun 2014, 16:23

Hello All,

I just wanted to share a little bit of info about how to efficiently model when planning on rendering. I get lots of emails about "How come my scene doesn't work right?", "Its not rendering, and I'm running out of memory!" "V-Ray keeps crashing my scene!"

These are all legitimate complaints. Everything should just work right all the time right?! While this is true, bad models can lead to bad results and especially crashes! There are a lot of ways to avoid those bad results though.

Modeling in Sketchup for renderings is always delicate balance because Sketchup is still a 32 bit program, meaning it can only access up to a little under 4gb of ram before it crashes. V-Ray has to work within these limitations as well because we are integrated inside of Sketchup. So having very clean efficient models is important.

That said, here are some tips for modeling in SketchUp for V-Ray:

Large scenes tend to crash quickly. If a scene is really big, try breaking it into completely different models, or layering things so that only the geometry visible in that scene is active and everything else is hidden or on a layer that is turned off.
Transparent materials slow V-Ray down when rendering, a lot. Turn any transparent materials (windows, water, glass) into a Reflective/refractive glass like material, or a VRayBRDF Material with those properties turned on, then delete the Diffuse layer completely, or use it as a Sketchup reference material by making it invisible to V-Ray. To do this, in your transparency map add TexAColor: White.
Trees, vegetation, furniture and other models from the 3D Warehouse should never be downloaded directly into a working model. Always open them in an empty scene and clean them up, and test them before adding them to a scene. Remove any layers, extraneous materials, or additional geometry that is not needed. Make sure its located at the origin of a model not way out in lala land and if its a big model (lots of polys) turn it into a proxy and bring it into the model that way (see our proxy tutorial for more info: http://help.chaosgroup.com/vray/help/sketchup/150PB/tutorials_proxy.htm ). This applies to all models downloaded from the warehouse. You never know how good or bad a model is until you put it in a scene. So test twice and render once.
Large scenes and over modeling are issues that everybody has trouble with. If you are rendering an a large scene, try and organize your views so that you have those items not seen in that view on a layer you can turn off when you are ready to render. If your not seeing it and don't plan to see it, don't model it because V-Ray will still have to process that extra geometry when you render. Also make any high poly models V-Ray Proxies.
Make sure all geometry is grouped. Large areas of un-grouped geometry can slow renderings down. Poorly modeled scenes will render a bad result. Make sure the scene is modeled clean and efficiently. Be sure all faces are oriented correctly (blue faces are back faces, white faces are front faces), this avoids any material confusion. Also be sure to model as closely to how the building (interior/exterior), car, generic model what-have-you will be built.
When rendering an extra large scene, use our 64bit workflow (see attached). It will allow you to render out very large scenes that will typically crash Sketchup.
Purge all un-necessary models, layers, styles, and materials from a scene often. A plugin that I find useful is the purge all plugin by TIG. You can find it here: http://sketchucation.com/pluginstore?pln=PurgeAll

**Side note when using that plugin, don't purge your materials from it. Undesirable results come from purging your materials on the Sketchup side. Always purge materials in V-Ray's Material editor.

I hope all this is helpful with your next project. If you have any specific questions on modeling or rendering, ask away!

64-BitWorkflow.pdf

jiminy-billy-bob · 13 Jun 2014, 19:27

@tedvitale_cg said:

Large scenes tend to crash quickly. If a scene is really big, try breaking it into completely different models, or layering things so that only the geometry visible in that scene is active and everything else is hidden or on a layer that is turned off.

Large scenes and over modeling are issues that everybody has trouble with. If you are rendering an a large scene, try and organize your views so that you have those items not seen in that view on a layer you can turn off when you are ready to render. If your not seeing it and don't plan to see it, don't model it because V-Ray will still have to process that extra geometry when you render. Also make any high poly models V-Ray Proxies.

For handling layers visibility at render time, use Layers Panel: