Two related questions about the awesome Path Tracer.
Q: When will it support (per-light) Indirect lighting intensity?
Since GPU Lightmass uses PathTracing code and CPU Lightmass supports indirect lighting intensity, I hope that GPULM (and hence PathTracing) will support it in future.
Q: Any chance there will be very preliminary AOV (Arbitrary Output Variables) support for MRQ?
It may be not even in the TODO list, but it would be extremely helpful for advanced composition.
Since there are many kinds of AOVs (see other GPU renderers, e.g. Redshift), I don’t expect Unreal will ever have them all, but I hope to have some minimal infrastructure to ease further custom development.
I hope it’s not too much work for Epic experts because Albedo and Normal are already computed and fed into OIDN, but there is no (easy) way to get them out in MRQ.
Actually we tried to implement AOV support on our own, but feels that it’s easy to destroy performance and/or exhaust CPU/GPU memory for non-expert graphics programmers like us.
We’re planning to implement (besides Albedo/Normal mentioned above): Direct Diffuse, Direct Specular, Reflections, Refractions and GI. No arbitrary LPE(light path expression) support is needed.
BTW: Some renderers (like Redshift and open source LuxCoreRender) support Light Groups AOV, that allows to change the power/color of individual light groups without re-rendering. It would greatly improve the workflow for some people (like us), but I understand it’s harder to implement efficiently.
If you don’t think these features will be implemented in forseeable future, some suggestions for implementing them on our own is greatly appreciated!
EDIT: Forgot a small question: when using Path Tracer with MRQ, the GPU utility (from Task Manager) is usually less than 10%, while other GPU renderers can usually get 70%~80%. Is it normal? Any chance to improve the GPU utility and save some render time?
We tried Nsight Graphics but even failed to capture a frame with Frame Profiler or GPU Trace Profiler so we have no idea what’s going on.
Maybe there are too many different materials (we’re using a lot of 3dmax exported assets). If this is the main problem, Will “updates to the material system” (mentioned in the original post) help in this case?