Iray test render taking a long, long time

inthanity

Is there a reason why an Iray render would take a super long time rendering the hair in a figure, then breeze through the rest of the figure without any prolonged delay?

I have a test render where I am rendering a figure, without anything else in the scene, and the hair (http://www.daz3d.com/krayon-hair-for-genesis-3-female-s) is taking over 30 minutes to render. I have a fairly decent new computer, with a "top of the line" NVIDIA card. I know I am missing something - settings of some sort, perhaps surfacing issues that need resolving, etc.

Thanks!

Richard Haseltine

A lot of hair seems very - in my view sometimes overly - glossy, and it is in layers. I think what happens is that a light path keeps bouncing between layers until it attenuates sufficiently to be treated as done or it escapes to infinity (certainly the blonde materials tend to render even more slowly than the brunette, which is consistent with this account). Lowering the glossiness of the hair (including the top coat setting) may help, as may lowering the Max path Length setting in the Optimisation group in Render Settings, but depending on the look you want those may not be acceptable (and they don't make an enormouse difference). Hair is also likely to be slower to meet the convergence criteria - you may well be able to stop the render manually at an acceptable level before it reports the hair as sufficiently covnerged.

UnifiedBrain

inthanity said:

Is there a reason why an Iray render would take a super long time rendering the hair in a figure, then breeze through the rest of the figure without any prolonged delay?

It's pretty normal, whatever render engine you use.  If there is a major slowdown, it's often hair or plant foliage.  That said, some hair products are a lot slower than others.  Rikki hair, for example, with stop everything cold if you don't turn off subd (the author even warns you about this on the product page). 

grinch2901

Richard Haseltine said:

A lot of hair seems very - in my view sometimes overly - glossy, and it is in layers. I think what happens is that a light path keeps bouncing between layers until it attenuates sufficiently to be treated as done or it escapes to infinity (certainly the blonde materials tend to render even more slowly than the brunette, which is consistent with this account). Lowering the glossiness of the hair (including the top coat setting) may help, as may lowering the Max path Length setting in the Optimisation group in Render Settings, but depending on the look you want those may not be acceptable (and they don't make an enormouse difference). Hair is also likely to be slower to meet the convergence criteria - you may well be able to stop the render manually at an acceptable level before it reports the hair as sufficiently covnerged.

This is interesting, thanks for posting that Richard. I have a couple of the OOT hairs for G3F and they're great but they add tremendously to the render time on my system. I've looked and the polys don't seem absurd, I thought it might be a surface thing but couldnt think what it might be. I'll experiment.  Thanks again!

RobotHeadArt

inthanity said:

Is there a reason why an Iray render would take a super long time rendering the hair in a figure, then breeze through the rest of the figure without any prolonged delay?

I have a test render where I am rendering a figure, without anything else in the scene, and the hair (http://www.daz3d.com/krayon-hair-for-genesis-3-female-s) is taking over 30 minutes to render. I have a fairly decent new computer, with a "top of the line" NVIDIA card. I know I am missing something - settings of some sort, perhaps surfacing issues that need resolving, etc.

Thanks!

How are you lighting the scene?  This particular hair renders relatively quick for me (compared to other hair products) and I have a four year old machine.  What materials are you using on it?

Novica

That hair renders at a decent speed for a typical computer. I can tell based on how long it takes me on my Alienware51 (which isn't typical. But by using its speeds on various hair, I know which ones may give folks a slowdown.)  I use that hair all the time in my product showcase thread (Art Studio) because it is zippy. What character, sets, and props are in your scene? I may have showcased them before and can call up the file and test it for you.

Novica

I did a test on Lindsey and the results were 5 minutes 18 seconds and about 3858 iterations for Lindsey, and with that hair, 4100 iterations and 7 minutes 20 seconds. So only 2 minutes for the hair. Original is 800 x 900.