How to handle volumetric lights?

In general, there are two ways of getting volumetric light effects with Cycles - hard way and smart way;)

Hard way - volumetric shaders

Cycles engine has implemented accurate volumetric shader. Volumetric shaders is pretty time consuming feature, plus some features are not fully implemented in GPU version of Cycles. In some complicated scenes getting volumetric right is the only option - but in case of subtle volumetric light effect, similar result can be archived much faster.

Smart way - faking volumetric lights effect

Requires little more effort at the beginning, but at the end you'll have nice, adjustable volumetric light effect done fast and noiseless. Most of computation can be done using RayPump acceleration - so we are talking about serious speed up to your workflow.

How it works?

Your final images will be mix of two layers - standard Cycles rendering (done without volumetric shaders whatsoever) and additional volumetric light layer, done in Blender Internal.

Sounds complicated? Actually - it is pretty easy to setup. As nice addition, strength of the effect is adjustable in the post-processing phase.

Cycles Scene

This is simple test scene. Nothing fancy, just rotating Suzanne with glowing eyes :) But we want those eyes to utilize some volumetric lights!

Rendering this scene it is most time consuming part - so, of course, I recommend RayPump to do the job! Meanwhile you can setup the second layer scene.


Blender Internal Scene

All the geometry in this scene is linked objects from Cycles scene. This way every change you make in Cycles scene will be instantly transferred here. Resolution is the same, rendering engine changed to Blender Internal. We render only Halo layer. The spot light is the actual only local object. It requires Halo effect turned on, with Step value > 0.

Rendering this scene is fast and noiseless. It can be easily done on your local computer. Meanwhile RayPump will get your Cycles renders. Once all the images are ready, all you need is to mix it down.


Adding volumetric layer

We'll use the Blender to mix the layers down. Nothing fancy - on the top of Cycles images we put the volumetric layer. It should have blend type of Alpha Over. You can adjust volumetric strength by setting Opacity.

Set your output format to whatever you want, for final video H.264 codec will be fine.


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Blender version used by RayPump

Blender (stable): 2.75a
RayPump Server: 1.170