[Bf-cycles] Feature: Recoloring of lights and materials post-render.

Peter Schmidt-Nielsen schmidtnielsenpeter at gmail.com
Thu Oct 11 16:34:30 CEST 2018

Hello folks,

I'd like to add a feature to Cycles (and Blender) to support post-render
recoloring of lights, and limited recoloring of materials. Post-render
recoloring of lights is a feature implemented in Maxwell, which they call
"multilights". Limited recoloring of materials can be achieved in Iray
using their Light Path Expressions. The idea is to support both kinds of
post-render relighting with a simple design, although not support the full
generality and flexibility of Iray's LPEs.

I think Cycles' users would benefit enormously from having such a feature.
The end user experience would be that a user could change color parameters
in specially marked lights and materials after the render, and the render
would update instantly to a completely accurate version of what the render
would have yielded with the different color parameters.

I have a description of my plan, which I wrote up about a year ago when I
first started poking around Cycles:


However, I'm not very familiar with the Cycles code base beyond the very
small amount of poking I did a year ago, and would love some advice and
direction on how feasible it is to implement this feature.

A TL;DR for my write-up linked above:

1) One can implement Maxwell-style "multilights" by just having one render
buffer for each relightable light, and writing path contributions into the
appropriate light's buffer.
2) I think one can implement Iray style post-render changes to material
colors without implementing a full-on LPE system, if you just track a
little extra data with PathRadiances and throughputs, and have a bunch of
extra render buffers.

Is anyone else interested in working on such a feature, or at the very
least giving me some advice on this?


-Peter Schmidt-Nielsen

P.S. I mentioned this about a year ago in #blendercoders, but I got busy
and didn't keep working on it. A few months ago someone in #blendercoders
recommended that I ask here.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.blender.org/pipermail/bf-cycles/attachments/20181011/f369a00c/attachment.html>

More information about the Bf-cycles mailing list