Compositor, cycles and sky

Support Compositing and Post Processing
#1

Hello all,

A quick question from someone new to compositing.

I am using the Cycles render engine. I would like to add a blur effect to an object in my scene using the compositor.

My naiive attempt at achieving this put the object in a separate render layer, and passed it through a blur node. However, I do not know how to mix the object back in to produce the composite. If I try mixing it with the other layer (containing ‘everything else’) then each layer contains the sky in it, so whatever I do the sky is affected by the compositing process.

Is there a way around this? Given that in cycles the light from the sky is a vital part of the render, the answer is not obvious to me!

Thank you in advance.

#2

use an id mask to isolate the object
if you don’t know what an id mask is, its explained at the beginning of this tutorial

#3

Thank you very much, that really helped.

One additional question: in my particular scene, the object that I want to isolate is occluded by, and passes through, an object with a glass material. When creating the id mask only the parts of the object that are not occluded are selected. Is there a way to select all of it?

Cheers!

#4

Im pretty sure that it can’t be done because the glass material will distort whatever is behind it