Waterfall Tails Hair slow Iray render time
I am experiencing slow render times when using the Waterfall Tails Hair. I would like to know if anyone else has experienced the same problems that I have or if anyone has suggestions to improve my render times.
I have conducted the following experiment to show the impact that the waterfall tails hair is having on my render times.
- Create a new empty scene
- Switch to perspective view and set to default location
- Set Iray render settings to default
- Change dimensions of render to 1080x1080
- Check OptiX Prime Acceleration
Here are the results of experiment with different hair styles:
- Aiko 7 No Hair - Iray iterations: ~400, Time: 51 sec
- Aiko 7 Waterfall Tails Hair Default Settings - Iray Iterations: ~740, Time: 2 min 50 sec
- Aiko 7 Waterfall Tails Hair Low Specularity - Iray Iterations: ~670, Time: 2 min 25 sec
- Aiko 7 Rochelle Ponytail Hair - Iray Iterations: ~450, Time: 1 min 15 sec
- Aiko 7 Leyton Hair- Iray Iterations: ~450, Time: 1 min 12 sec
- Aiko 7 Toulouse Hair - Iray Iterations: ~425, Time: 1 min 5 sec
This experiment shows that the Waterfall Tails Hair adds about 90-120 seconds to the render time; while, most other hairs only add about 15-25 seconds. This means that the Waterfall Tails Hair causes 4-5 times longer render times. I first notice this problem when a scene rendered in 20 minutes with the Rochelle Ponytail Hair and 1 hour and 40 minutes with the Waterfall Tails Hair. Is there a reason for such a increase in render times? Is there anything I can do to prevent the Waterfall Tails Hair from increasing my render time by such a large factor?
Machine Specifications:
- MSI GT72 Dominator Pro Laptop
- OS: Windows 10 Pro (64-bit)
- CPU: Intel Core i7-4720HQ CPU @ 2.60GHz
- RAM: 16 GB
- Graphics Card: Nvidia Geforce GTX 980M
- Daz Studio Pro 4.9.2.70 (64-bit)
Comments
That's the glossiness of the hair allowing the light paths to bounce around before they reach a point where no further bounces will affect them greatly I think - that's why the lower glossiness renders more quickly. One thing you can try is adjusting the Maximum Path Length in Render Settings, under Optimisation, but not that anything under 6 will not render the eyes correctly (any positive number under 6 - the default -1 keeps bouncing until, I think, some brightness threashold is crossed). I've found that to give a slight speed increase with hair.
Thank you the tip about the glossiness. I have tried a few quick test by changing the Maximum Path Length and adjusting the glossiness of the hair surfaces and I was able to get the render time down to 1 min and 40 seconds with decent looking hair. I am sure with more fine tuning and testing I will be able to get the look that I am going for without larger render times.
Not that it's something you are likely to want to change, but the hair colour also makes a difference. I've been going through trying out the (large) backlog of hair models I'd bought and it's noticeable that blondes almost always take longer than brunettes - presumably because there's less attenuation (which is the word I wanted earlier) on the bounces with the lighter surface.