Render Layers

A multi-pass render breaks out the different components of the beauty pass. Usually these are the diffuse, shadow, occlusion, and specular passes. These can then be composited together to get the final image.

Render layers allow you to do multi-pass renders very easily. Each render layer has overrides on the settings for render components, render settings, model and light membership, and materials.

The power here comes in being able to adjust the layers seperately in the comp, rather than re-rendering the full image. The occlusion pass is often slow, so it's nice to be able to play around with tinting the specular pass or diffuse pass without re-rendering the occlusion. Drop the layers into Shake or Photoshop with the appropriate layer operations and you can tweak away.

Steps:
- Select all the objects and lights you intend to render.

- Create five new render layers, choosing the icon with the blue ball in the render layers window.

- name them, from the bottom up, diffuse1Layer, diffuse2Layer, shadowLayer, occLayer, specLayer.

- RMB-click on each layer to choose the appropriate override preset based on the name of the layer.

- for the second diffuse layer, create a material override by clicking the shaderball icon on the render layer and dragging a different material on car objects.

- turn off the render switch ("R") for the second diffuse layer.

- Set the composite operations to:

specLayer = Screen
occLayer = Multiply
shadowLayer = Multiply
diffuse2Layer = Normal
diffuse1Layer = Normal


- In the render view window, choose Render > Render All Layers ... (options) and switch to Composite and Keep Layers. This will save each pass to the Render View buffer and comp them all together.

- Render the frame.
You'll see each pass render and get stored in the buffer. You can then scrub the horizontal bar under the Render View to check out each pass. Shadow pass lives in the alpha channel. The final image is the comp.

If you want to try the different paint color, toggle the "R" render switch for the Diffuse1Layer and Diffuse2Layer. Re-render and be amazed!

Now, to really make use of this you should do a batch render. First, pick the masterLayer render layer and then open the Render Settings. Change the output type to .psd layers. Then do a batch render. Head over to photoshop to play with the results.


Scene file: beetle02.ma.
Classicbody.jpg
headlight.jpg
chrome.jpg
TyreTexture.jpg