[Mini-Tutorial] Iray Progressive Render Settings

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This weekend I got a chance to talk to the DAZ 3D developers about the progressive render settings and what they do.  Here's some clarification on those settings.  I did not know some of this myself until I had a chance to ask this weekend!

The progressive render settings are found in the "Render Settings" tab in DAZ Studio and the "Editor" portion of that tab.  The important settings are:

Max Samples:  Short version: The Max Samples count is the maximum number of samples Iray will achieve before it stops the render.  The default number is 5000.  How long it takes to get to 5000 samples varies by what kind of hardware your computer has - it will get to 5000 much faster on an Nvidia graphics card than a CPU or an AMD card.

Longer version, as best I was able to learn from web research: In any kind of rendering, the engine is trying to depict a 3D image as though it were in real space; in real space your eye views all images as continuous, but in the rendered image, the image has to be broken up into a finite number of pixels.  The process of sampling is how a render engine tries to compensate for working with those pixels and the fact that visual information "stops" between them, creating the visual artifacts that you probably associate with a "bad" Iray render.  But importantly for now, the more samples Iray calculates, the more it can smooth out the 3D space between the pixels into a continuous image without "jaggies" or "fireflies."  More samples make a smoother, more complete image. 

Max Time (secs):  Iray can also be told to stop the render when a certain number of seconds have passed.  The default value is 7200, which is two hours.

Important take-away: Iray will quit when it gets to ONE of these two values, normally.  If it gets to two hours but has only done 2000 iterations or samples, it will still quit.  If you have older or lesser hardware, you need to set the time much higher to get the same samples.

Rendering Quality Enable:  If this is set to OFF, Iray will just use the Max Samples and Max Time to determine when render stops.  If you want render time to go just based on those, turn this to OFF.  If it is off, the Quality and Convergence sliders don't matter.

Rendering Quality: This linearly increases render time each time you raise the number: 2 is double the value of 1, 3 is triple the value of 1, etc.  It overrides the time and samples counts.  Use this only if you really want to try the "render forever and tell it to stop when I like how it looks" method.  Otherwise just leave it at 1.

Rendering Converged Ratio:  This is a function of the time and samples counts.  I did not realize this until a dev told me, but apparently this is actually impossible to get to 100%, so to avoid errors it's better to converge to 99.9% instead if you want to make sure everything runs long enough without resorting to the Quality setting.  I've probably caused myself and other people some crashes with this, and I'm sorry about that.
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tora-no-shi1369's avatar

I have found that setting max time to 0 removes the timer from the render and only uses the samples. I use it because i had renders that took days to get done with my old computer. The computers I use don't have a GPU only a CPU. So, I remove the timer every render, just in case it takes longer. I need to post some of my more recent work as my quality has gotten a lot better over the time I have been gone frome here.