A few months ago, I discussed some of the new features available in Maya 7, and I mentioned that Maya includes render layers. Previous versions of Maya also included render layers, however, they were not nearly as powerful as in Maya 7. Previously, many artists had to use different versions of the same scene, each with its own render and lighting setups that would be rendered separately and put together in postproduction. Now in Maya 7, the render layers do just that: treating each layer as a separate scene!
When you create a layer, you can select which channels to render. Say you only want to render the diffuse channel of your shader, or maybe just the specular. Maybe you don't want your objects to cast shadows, or you want to turn off "primary visibility" for every object in the layer. You can do that in the "render flags overrides". The render layers also include some presets for your scene, such as diffuse or ambient occlusion. The image above actually has an "ambient occlusion" preset applied to layer1.
The workflow to create a render layer is similar to creating a display layer. First, you select the objects you want that layer to include, and then you create the layer. A layer will include not only objects, but also lights that you may have included in your selection. You can then add or remove objects without a problem. Each object can have a different shader per layer. This means that the same sphere on my scene above can have an ambient occlusion shader in layer 1 and a blinn shader in layer 2. To apply different shaders to the same object, just go to the layer that you want to work on, then assign the shaders. When you select a different layer, you will see the shaders switching automatically. If you want to have the same shader applied to all objects, you can also use a "material override". Note, that if you use a material override, you won't be able to assign any other material to any object, untill you remove the override.
I can put a light on both layers 1 and 2, and then set a "layer override" that will tell the light not to cast shadows on layer 2. I can even change its color for one of the layers. Maybe you want an object to only cast shadows for layer 2, then you can make a layer override that will tell it to turn off "primary visibility" only for that layer. Attributes that have layer overrides, will show in orange for that specific layer. Something you have to remember, is that you have to create the layer override before you change its value, or you will actually be changing that value for every other layer as well.
You can even create layer overrides for render globals settings. By default, all layers will utilize the same render settings, unless you are using a render layer preset (they will even use the same renderer). If you wanted to change some render settings for that specific layer (for example, turn on final gather only for one layer, or render it using Mentalray instead or Maya Software). You can also create a layer override for those settings, and then change it as you please.
Many users wonder why it is so useful to render in layers. Sometimes it will cut render times, because it's easier for Maya to calculate one specific shader, rather than layer upon layer of shading networks. Sometimes it will help to make things easier for you (for example, you can decrease the specularity in post rather than rendering again). Rendering in layers can bring you many benefits that sometimes are overlooked, but now with the new render layers system you can take advantage of those benefits.
If you haven't done so, download the Maya PLE from Autodesk and see for yourself.
copied, printed, or reproduced in any manner without written permission from the artist.
Animation Alley is a regular featured column with Renderosity Staff Columnist Sergio Rosa [nemirc].
Sergio discusses on computer graphics software, animation techniques, and technology. He also hosts interviews with professionals in the animation and cinematography fields.