Mattes from a blend material
The easy way is to buy Deex's vray arsenal: http://arsenal.deex.info/wordpress/
A less-easy way is to use this trick: http://forums.cgsociety.org/showthread.php?t=978866
Take your mattes, feed them into a layered texture to get the rgb mattes setup as you'd like, then feed that directly to the material_id property of the SG of the blend material. Output a material id render element, done.
Example scene: File:vray_blend_mattes.ma
Render vertex colours
Here's an example in maya 2014. File:vertex_colours_vray.ma
First, paint some colours on a mesh.
- Right click on a shape
- Paint -> mesh -> <shapename>-vertexColorsRGB
- Bring up the tool panel to choose colours
- Paint stuff
Next, read that in Vray:
- Create a VRayVertexColors node
- Change its mode to 'Set Name'
- Type in the set name, it'll probably be colorSet1. To check this:
- Select the mesh
- Polygons menu set > Color -> Color Set Editor
- Connect the VRayVertexColours node to the diffuse of a vray material, or any other parameter you want.
Select the curves, Create -> VRay -> VRay renderable curve -> Apply <stuff> to selection.
You can then change attributes on the newly created node to change width and taper, and assign materials.
Assign volume to object, but be able to have camera go inside it
VRay is amazing at volumes, but the standard behavior is a little confusing if you assign a vrayEnvironmenFog to an object via the volume slot on a shading group. It'll render happily as long as the camera is outside the shape, but disappear once its inside. Vlado on the forums hinted it was possible to do, these are the steps. Basically you apply it as a global fog, then constrain it to a shape using the envfog as a set:
- assign an envfog via the render globals -> vray -> environment section
- create a shape that'll be the bounding volume, assign a vray material, set its opacity cutoff to black so its invisible
- window -> relationship editor -> sets, select the envfog on the left, shape on the right
Done! fly your camera through the volume, bask in its foggy goodness.
Per light render elements with Light Select
Per light aov's, lightgroups, call them what you will, they're handy. Vray does them just fine, but they're underdocumented, and I didn't have time to watch a 16min youtube tutorial. Doesn't anybody read anymore? ;)
- render globals -> render elements
- add a Light Select element, in the AE set the 'vray name lightselect' to something useful, eg 'practical_lights'
- window -> relationship editor -> sets, select the light_select node on the left, lights on the right
- repeat this process for each light group you want split
- do a test render with the vray framebuffer, you should see your passes in the dropdown lister
Use the vray framebuffer
It's SO much better than maya's render view, which should surprise no-one. When working with floating point, high intensity lights, its really important to be able to check your work at various exposures, with and without a curve, a lut, and do it quickly. Vrays' framebuffer lets you do all this. A minor annoyance is that maya insists on popping the render view up each time you render, I just slide it nearly offscreen so it stops bothering me. Also lets you easily see all the render elements you're creating, which is nice. Which leads to...
Vray framebuffer render history gets slow with lots of render elements
Makes sense if each time you click 'save' on the render history, it has to copy 10 render elements to your temp drive. Turn off the render elements if you don't need them with interactive tweaking. Note that you can turn off the render elements with a render override if you need to, handy if you have several render layers, but just need elements on a few ( render globals -> render elements -> disable/enable render elements checkbox at the bottom)
Subdivs mult as a quick preview quality/render quality slider
Render settings -> Settings tab, set the subdivs mult to 0.1 for fast previews, back to 1 for final rendering. Just don't forget before sending to the farm!
- best solved on the material first, reflection subdivs
- 8 is default, 16 nearly removes completely
- can then go to the light and reduce reflection contribution if need be
- finally try render settings, max subdivs and noise threshold
If you're being all physically correct (and why wouldn't you be?), you'll set reflection to fresnel and link reflection IOR to refraction IOR, but the default value is too low for glossy reflection. Dial it up to 3 or 4 to start with.
Multiresolution exr converter
If you have any crazy sized, exr's (I'm currently loading 5 14k exrs for a skyline projection, beat _that_ ), convert them. Makes vray much happier. Under windows its a nice little gui that can batch process: start -> all programs -> chaos group vray -> tools -> image to tiled multiresolution exr converter
Distressingly easy to use. Found it funny that maya had a harder time throwing around the bounding box version of a crowd, even instanced, than vray had rendering it. Why you suck so hard at lots of transforms maya? WHY??
Why VRay? Mentalray is fine!
I don't think anyone would really choose mentalray over other renderers, but just in case....
If you've only ever used mentalray, vray feels like mentalray done right. It's as tightly integrated into maya as mentalray (prman always feels like a bolted on thing), can be tuned and fiddled like mentalray if you like to create light caches and precompute blah blah, or can put it into brute force mode like arnold and just path trace all the things. The standard material is similar to the mia material but much easier to use, volumes are dead simple and fast, has actual working aov's/eoc's/render elements that are a no brainer to setup. It also ships with a cuda/opencl accellerated renderer called vrayRT, which is integrated with maya's IPR mode, good for fast tweaking and lookdev. The forum at chaos group is lively and helpful, builds are released almost every day, the devs are visible and engaged.
Yes it costs money, but so do brain cells in the long run. Ditch mentalray, you know you want to.