Maya 2012 Tutorial
How to Render Layers to Composite Layers in Maya
Render Layers allow you to render your objects one at a time so they can be reassembled in a compositing program (i.e., Photoshop for stills and After Effects for animations).
In this example we will create a scene with two objects and a light. There will be three rendered images, object one, object two and the shadow cast on object two.
This method is used to give you additional flexibility in creating your final image. Since the image is broken into a separate layers, each layer can be adjusted in post production without having to re-render the scene in Maya.
The methods described in this topic work with Maya Software Rendering. For Mental Ray it is a completely different process. For more information, see topic, Render Passes and Mental Ray.
Add a polygon plane to your scene by choosing Create > Polygon Primitives > Plane. Make sure to start and set your project. For more information, see topic, Starting a Project.
Add a text object to the scene by choosing Create > Text. For more information on creating text objects, see topic, Text Object.
Add a spot light by choosing Create > Lights > Spot Light.
Position the light in the scene so it illuminates the text object.
Select the light and open the Attribute Editor. Activate Depth Map Shadows by opening the Shadows and the Depth Map Shadow Attributes sections. Click the Use Depth Map Shadows checkbox.
Render your scene by clicking the Render Current Frame icon to make sure your light and it's shadows are working correctly.
Select the light and the text object and open the Channel Box.
In the Layer section (lower portion of Channel Box), click the Render tab.
Choose Layers > Create Layer from Selected. This creates a render layer for the text object and the spot light.
Name your layer text.
Choose Layers > Create Empty Layer. Rename your new layer plane.
Choose Window > Relationship Editors > Render Layers.
Click plane in the left column and click the light and plane object in the right column. This is just another way to accomplish the same goal as Step Nine.
Right-click the Master Render Layer and choose Select Objects in Layer.
Click the Create New Layer and Assign Selected Objects icon in the upper right corner of the Layer panel.
Name your new layer shadow.
Click to select the shadow layer. With nothing selected in the scene, right click the shadow layer name and choose Attributes.
Open the Render Pass Options section, deselect Beauty, then select Shadow.
Open the Render Settings window and select an image format that supports alpha channels (i.e., targa or tiff), then Batch Render your images. For more information, see topics, Rendering an Image and Rendering a Movie. Once rendered, the three images can be found in the images folder, inside another set of folders labeled to match the Render Layer names. The images can now be opened in Photoshop or After Effects for final compositing.
If you are compositing in Photoshop, double-click the layer icon to convert your layer into a transparency layer. Command click (PC - Ctrl click) the alpha channel to make a selection. It can be used as a layer mask by clicking the Layer Mask icon.
Step Twenty One
By using render layers you have editing control of the text, shadow and plane.
Where's My Shadow
The shadow is hidden away in the alpha channel. As you import into After Effects, the alpha channel is automatically loaded. For Photoshop you will need to do a little manual tweaking (see Step 20).
More than Just Beauty and Shadow
Using this method you can also separate Specular, Color and Diffuse images by selecting the checkboxes in the Render Pass Options.
For clarification, Beauty means all of the images combined. The Diffuse pass doesn't include reflections.