Weird Iray Interactive lighting glitch

Diaspora

Hello, I'm experimenting with using Iray Interactive mode for rendering animations cause it can get very good results in a fraction of the time of photoreal.

I'm having a weird lighting problem though where sometimes the environment light, as more iray iterations occur, it will make the shadows get brighter and brighter.

I was doing a test animation earlier where one frame it behaves as expected and in the very next frame, no drastic camera changes, no keyframed lighting changes, suddenly it's got that runaway brightness issue. 

Has anyone else experienced this? I've tried messing with every setting I can think of but can't quite seem to shake this issue and it's becoming a showstopper. 

crosswind

Better post a screenshot... and have you tweaked the params under the mode of  Interactive Biased? - Ray Bounce, AO relevance, etc...

Diaspora

You're right, I'll get some screenshots up soon.

In fact, is sharing links to scene files allowed?

I was able to narrow down the issue a bit which I did by going to Shadows & Lighting > Indirect Light Mode >

and switching it to <none>

Obviously that changed the behavior of the renderer and final look but it does show that the issue has something to do with Interactive's Indirect Lighting.

Richard Haseltine

Scene files may be shared as they do not embed the content but link to it - that does mean that if they use anything other than the default content you will need to tell people what it is, and they will get errors if they do not have it or do not have it installed.

Diaspora

I see! 

In that case I will make a scene file demonstrating the issue with just the starter content. 

Diaspora

But question that might get me to the bottom of this, from what I've learned so far, it seems that this issue is caused by interactive mode's indirect lighting kicking in based on the render camera's distance from the object whose materials' diffuse layer is being affected.

This seems like it would be a pre-set variable somewhere but even through trial and error I wasn't able to find anything like that.

Do the render settings have some kind of 'hidden' mode the way the parameters tab has an edit mode?

crosswind

I just posted the different indirect light effects as below...

Indirect Lights are 'simulated' with Interactive Biased Mode (non real PBR). The default Diffuse & Glossy may have the 'better effect' but it will take more time to render, so it's up to your preferences...
Comparing to Photoreal, there's no real SSS effect and related shadow in Interactive Biased, and the 'simulated glossy effect' is also 'fake' which is not based on real physics-based raytracing...

As for 'hidden properties', yes there're but they depend on the Render Mode you select and/or the parameters you set. There's no 'Edit Mode' in Render Settings.

PS: The test scene uses the default HDR + one top spotlight...

Diaspora

So, try as I might, I can't get the indirect light mode glitch to manifest when I create a fresh scene file just from primitives and default assets.

I want to suspect that maybe because I'm seeing this happen in somewhat old scene files (or new scene files that were created from old scene files) that maybe there are some kind of 'vestigial settings' that have made their way through the sort of scene file 'generations' and consequently are causing the problems?

For testing purposes, is there some kind of good way to scrub all Iray settings out of a scene file so that I can just try to rebuild all the render settings cleanly?

crosswind

Not sure of that indeed unless we have your scene files.... As for 'rebuilding' settings, Photoreal / Interactive are both iray Settings, I really don't know how to scrub them all but only know there's a function: Restore Render Setting Defaults...