Compositing the Final Image
This section covers the compositing of the two passes you've created.
Our passes so far have given
us a volumetric light pass (which could also include a
whole scene if desired) and a volumetric caustics pass (which includes only volumetric
caustic light). All we need to do is overlay the volumetric caustic pass over the top of
volumetric light pass (or background) pass.
The FX Tree Configuration
This will probably be the
simplest FX Tree configuration you ever use. First of all bring
up the FX Tree by pressing <Alt> + 1.
Now select Passes->Get All Passes.
Then choose Operators->Composite->Over.
The last operator we need is a file output operator. Operator->Image->File Output.
Now connect the FX Tree as below.
Double-click the FileOutput
node to open it's property editor. If you wish to customize
the output file(s) then click the ... to browse for a new output file.
Now click render on the property page then click render in the dialog that comes up.
Your final composite should look something like below.
That's it - you're all done. You can download a copy of the finished scene here.