What is the rule on lighting and Render time in Iray?

DDCreate

I know it all varies but is it easier/faster for Iray to Render if there is more lighting or does that slow it down? I ask because I have an environment I am working with that has a main room, a smaller back room and a hallway. I set the lighting in each area and did test renders until I was satisfied. My question is, if I do a render of 2 character in the main room, is the lighting in the other room/hallway slowing down the render or does it not mater? Oh also! As a matter of habit, before I render, I select EVRYTHING in the scene and give it a whack with the UberShader. Am i doing myself any favors there?

Just a couple curiosities I had. Thanks for any feed back!

BeeMKay

Yes, it woul. Even if you are in an enclosed room, and have the HDRI active (instead of Scene Only), the light source is calculated. Converting to UeberBase before you start rendering saves a bit at the beginning of the render, as the auto-convert doesn't have to work, then.

DDCreate

I don't think I have anything HDRI going. I load the scene, decorate it the way I want and then install my lighting. Would putting it in Scene Only help? Where is that option?

BeeMKay

If you render Iray, there's a HDRI default map to light when you use the "Dome&Scene" setting.

In the render settings, go to the Environment and change Environment Mode. I've marked the default HDRI map, too, in the screnshot.

Word of caution, though. If you have windows in your room, the HDRI will supply light througfh them, so if you switch to Scene only, you'll lose that light.

 

DDCreate

I'll see what the difference is between the two. Basically I was just trying to figure out the best way to render an environment that contains rooms/props/lights that I don't even appear in the render I am doing at that moment. So just to make sure I have this. If I switch to Scene Only, that will be the most efficient way of rendering a multiroom environment but it will make a lighting difference from the lack of HDRI

dreamfarmer

Speaking of which, does the amount of space the light has to travel around the set matter? I was working on converting The Old Warehouse to Iray (and cleaning it up/repainting for Secret HQ use) and renders of even a well-lit small corner took _forever_. Like at 3 hours in, it was only at 15% converged, which is way longer than renders in a smaller, much more complicated space with a character present. I've been trying to figure out why and if I can do anything to reduce this timeframe.

(Although the render, stopped at 15% converged, looked pretty darn good. Which just added to my confusion....)

Tobor

Convergence is an internal estimate based on algorithms. Sometimes those algorithms get hung up on the "corner cases" that don't match the usual cues. You can't (and shouldn't) rely on Iray to tell you when a render is complete. Only you can do that. The various stop-at settings (time, convergence setting, etc.) are really there for unattended rendering, not as a true metric of quality. 

Distance doesn't matter unless there is so much fall-off of the light that the scene is dim. That doesn't seem to be the issue based on your description, so the more likely causes are things like lots of reflections, pattern noise in textures (these are harder to estimate because they look like unconverged pixels), excessive highlights, over-reliance on complex meshes as light sources, and so on.

dreamfarmer

Aha! That is incredibly useful! I was just poking at Everyday Primitives (the terrain one), applied a ground texture, started it rendering and.... same thing.  Looks fine, but IRay will clearly work at it _forever_ if I let it. To be honest I have been assuming that 'letting the render complete' was something I should always be doing, and just be adjusting the quality settings if I wanted it lower quality. I always felt like a cheater when I declared something 'good enough' and stopped it.