' Iterations.....'

jontaylor99

Can anyone explain this for me please?

I've been using DAZ for quite a few months now and I'm generally fairly pleased with my progress although there are still a million things I don't understand, here is this weeks example.

I set up a scene, nothing too complex but fairly large size wise and having an amount of water in it I decided to up my max iteration settings to 9000 and my time was set to 2 1/2 hours.

Now, everything was going fine and the picture was starting to look really good in the preview window but then I noticed it had already used an awful lot of the '9000' that I set before hand, sure enough it had used up a lot because the render stopped at 9000 but had only rendered to 64% on the scale meter, now here's the funny thing that I don't understand!

Not having time to start it all off again I saved the scene exactly as it was, settings, cameras, figures, the whole works saved, yesterday I had chance to reload the scene and start again but this time I upped my iteration settings to 15000 thinking that would be on the safe side, I left the time value at 2 1/2 hours. To my amazment the whole scene this time rendered to 100% and looked really good but had only used just over 6400 of the iterations. How is this possible and why does it happen ? The scene I reloaded was exactly the same as previously saved, I never changed anything at all apart from the max iteration setting.

Also I'd like to know if there is any way of knowing a rough idea of what you will need to set 'iterations' to before you start a render ?

 

Thanks for reading this far (if you have).

DrunkMonkeyProductions

Got one question first.

Did you let it run for the  2.5 hrs or did it end sooner?

 

jontaylor99

DrunkMonkeyProductions said:

Got one question first.

Did you let it run for the  2.5 hrs or did it end sooner?

 

Hello DM...... Yes it finished well under the 2 1/2 mate, it always does with any render I do, it's just a setting that I always put in to safe guard running out of time.

kaotkbliss

There are 3 settings which will stop a render.

One, as you found out is the itterations

The 2nd is the time limit

and the 3rd is the convergient ratio which is basically what percent of the pixels have not changed since last itteration. The default is set to 95%

 

the render will stop at whichever of these 3 settings it hits first.

Tobor

You use Max Time, Max Samples, and Rendering Converged Ratio to control the stop-at values by which Iray will consider the render complete. The FIRST thing to do is make your render as efficient as possible, rather than trying to simply up the time, samples, or ratio, in the hopes you'll somehow get a good image from it. Efficiency depends on things like lighting amount and type, proper use use of shaders, number of reflections, and other aspects. This forum is awash in suggestions on how to improve these.

Why you got by the second time with fewer iterations is probably related to some "hints" file no one other than nVidia and Daz knows about, but likely exists between renders somewhere. I've noticed this too on occasion, and there is no rhyme or reason. Iray and its use in D|S is woefully underdocumented, and this is for the everyday features we use, let alone under the hood stuff.

 

kaotkbliss

whoops, you're right. I mixed up itterations and samples.

jontaylor99

OK thanks guys, that at least has given me a little more understanding of what's going on.

barbult

You can alter your number of samples or render time limit and resume without starting over. One caveat, some of the things you are allowed to change do seem to make the render start over, but samples and time just continue where you left off.

kaotkbliss

Gah! I had never noticed that sidebar before. Thanks for the bit of info

barbult

kaotkbliss said:

Gah! I had never noticed that sidebar before. Thanks for the bit of info

Like most things, I learned it from someone else on the forum.