Digital Tutors: Advanced Compositing Workflows in Maya and After Effects
Here are some good tips for setting up render passes and compositing them in after effects:
1) Use contribution maps in your render layer to separate elements out. We can isolate and color-correct them later. Associate the respective geometry for each contribution map and name them.
2) For render passes, we assess what we need. Backgrounds should usually do just fine with beauty pass alone. The workflow is to specify the passes we need and associate them with the contribution map for each render layer.
3) In beauty pass attributes, we might want to turn off hold out for background, which creates an alpha for the occluding character, to avoid problems with outlines.
4) Here is a list of passes that the following material can render:
ambient material color
5) Depth pass are better split into foreground and background. Make 2 depth passes for that matter.
6) To split up subsurface scattering effects into their own passes, we first need to make 3 custom color passes. Name them front_scatter, back_scatter and diffuse. Associate with the contribution map. Go to the misss shader responsible in hypershade. Create 3 “write to colorBuffer” nodes in hypershade and rename them (frontscatter, backscatter, diffuse). Now connect the front_result of the misss shader to frontscatter etc..
7) We can make a render layer for the ambient occlusion pass, excluding things like fur. Create an mib_ambient_occlusion shader and connect it’s default to the out color of a surface shader. Increase the samples and set the max distance according to scene. Assign the surface shader as a material override for the render layer.
8) We can make masks on a separate render layer for the main character we are rendering. Make a render layer for this matte pass. For things like fur, we could make material attributes override in its shader to change color.
9) For file naming, we can set them in render settings by right clicking the file name prefix and choosing whatever tokens we need. An example could be renderlayer/renderpass.
10) If we need HDR or EXR formats, we need to set 32bit in framebuffer under the quality tab.
11) Working in 32bit high resolution images may be a pain for AE. We could make use of proxies.
12) Use a lightwrap effect to better sit your character in its environment. All we need is two copies of the alpha matte, one of which is blurred and inverted. Then just use the combined alpha on the background.
13) If we need to paint on our matte to fix problems, we can apply a paint effect and use the preview window with the brush to paint.
14) Use the lens blur effect to composite a depth of field pass. If we encounter problems with black areas of the dop pass (being treated as infinitely far away), we could use a minimax effect (maximum then minimum operation) to eat away the black areas.
15) We can add realism by creating chromatic aberration which happens in photographic lens. Duplicate the comp into 2 and use the set channels to separate RB and G channels. Scale them around.
16) Add grain to your final images!