Need Help with Compositor/Render Layers

Support Compositing and Post Processing
1

Hello BlenderArtists,

I am currently working on a project in which I’ve modeled a bmx bike, and I’m now in the process of using the compositor to try and give the render a bit of a kick. This is my first time using the compositor, and I’m having some trouble. I don’t fully understand how the Render Layers work. So far, via trial and error, I’ve concluded that in the compositor, the only way to get multiple render layers to actually appear in the render, is to use a “Mix” or “Add” node in order to have all the render layers visible.
(I’m most likely wrong, and I’m hoping someone can explain the proper method:confused:)

Anyways, attempting to make a glare effect on the rims of the bike, I end up having the rims glow over the frame and the chain.

http://i34.tinypic.com/25rcfae.jpg
25rcfae.jpg1280×1024

As you can see, the glowing of the rims shines right through the frame and chain. Im wondering if there is any way to the have the rims and frame (which I put in seperate render layers) to not affect each other.

Here is my composition (Am I doing something stupid?)

http://i38.tinypic.com/546qmu.jpg
546qmu.jpg1600×930

I really hope it’s possible to get what I’m after, because the composition really gives it the pop I’m looking for.

Thanks very much to all for your help, I really appreciate your time and effort.

2

The compositor is brilliant. The more you get to know it, like many blender features,
the better it is.
One way I would suggest you could do part of what you want is to assign an ‘Index’ to the rims.

Set a PassIndex of 1in the ‘object and links box’ (Select the 3 pointy arrows next to the material box). AND then enable ‘Index’ in the bottom of the ‘Render layers’ box.

An output from your render layer box in the node editor screen will then appear that you can connect to an ‘ID Mask’ node (Add->Convertor->ID Mask).

Set the ID value to 1 in this node, then if you connect the output from this node to a viewer node it should show a black and white (alpha) version of your object that you defined as Pass Index 1. ie it won’t be over the parts of the bike that it should be under.
Sorry that’s probably clear as mud, but best I could do.