If you haven’t figured it out already, I’m a big fan of using Iray for rendering with Daz Studio 4.8+. While spending time cracking out on it, I’ve figured out a few things I thought were important and worth sharing. I think they’re especially good to know if you’re considering buying a new GPU.

With that being said, I’m just going to dive right in…

1. • If you’re tweaking a scene, rendering then canceling, rendering then canceling, eventually your VRAM will get full and Iray will stop using your GPU for rendering and switch to your CPU. Which typically equals longer rendering times. It can even happen when letting the render finish completely, though, for whatever reason, it seems to manage the VRAM better in this second scenario.
   • The solution, when it switches over to your CPU, you have to close Daz Studio and restart it. Then everything will be back to normal again. Also, if you keep the number of render preview windows open at a time to a minimum, when your Render Target is New Window, it seems to help the VRAM from getting as full.
   • I have verified that this is a known issue with the Daz Development Team.
   • When it first happened to me I thought one of my GPUs went out. When Iray switches from GPU to CPU I can hear it, because the fans on my water cooler crank up. I then fired up my GPU monitoring software and saw one of the cards wasn’t being used. Long story short, I finally realized the only reason the other card was running was to run my monitor, my GPUs were fine, then I contacted DAZ…
2. • When using Iray with multiple GPUs, all the data being processed for rendering has to fit into each card’s VRAM independently. Which means if you have a 4GB card and a 6GB card, and the scene to be rendered requires over 4GB VRAM, the 4GB card will be excluded.
   • I’ve verified this with folks from both Daz and NVIDIA.
3. • If your NVIDIA card doesn’t have at least 4GB VRAM, Daz Studio will default to CPU rendering.
   • I also confirmed this with Daz. (After the public release of Daz Studio 4.9.)

Well, I hope you learned something! If you found this post valuable, don’t forget it to share it with someone else.

Catch you on the flipside…

LayLo

With the inclusion of NVIDIA Iray with Daz Studio 4.8+ we now have the ability to render using NVIDIA GPUs. While that’s old news, you might be wondering what kind of performance increase to expect with the addition of another GPU. Well, I did anyway…

Lucky for you, I tested just that…

In the picture you can see I have my SLI cable installed. Disable SLI before rendering for the best performance with Iray. You don’t have to remove the cable, just disable SLI in your NVIDIA Control Panel.

I also measured the difference in power consumption (watts) using a single GPU vs. both GPUs, as well as render times in both Daz Studio 4.8 and Daz Studio 4.9.

First, the hardware used for the tests:

Second, the method:

I started off by rebooting my computer. I then fired up Daz Studio and loaded the scene I would be using for the tests. For the single card power consumption tests, I only had one GPU installed in my computer.

I rendered the scene once to make sure the first test results wouldn’t, coincidently, take extra-long due to loading the textures and geometry into the card’s VRAM. From there I proceeded with the testing.

And, the results:

Conclusion:

Iray scales exceptionally well with the addition of a second GPU! By adding a second GTX 980, I cut my render times by 53%! Now, the extra 3% beyond the 50% is probably just due to variances in render times. You could render the same scene, with the same hardware, a dozen times and probably never end up with the exact same render time twice.

Here is a link to get an idea how individual cards perform by themselves:
http://www.migenius.com/products/nvidia-iray/iray-benchmarks-2015.

I’m extremely curious if one could expect the same kind of improvement (33% faster than compared to the two cards) with the addition of a third GTX 980. Currently, with the two GPUs installed in my system, they both get 16 PCI Express Lanes. Due to the fact my motherboard/CPU combo can only handle a total of 40 PCI Express Lanes and the way my MB manages them, if I installed a third card they would get configured into a x16, x8, x8 configuration. Unfortunately, I don’t know how this would affect scaling.

I thought it was interesting that running the cards at 1400MHz vs. 1279MHz, roughly a 10% increase, only cut 10 seconds off the total render time using the dual GPU configuration. I didn’t test the difference with a single GPU.

Please make sure your system can handle an additional GPU before you run out and buy one. Also, keep in mind if I were to install a M.2 SSD it would disable my 4^th PCI Express slot and consume x4 PCI Express Lanes. Meaning I could have either 4 GPUs, or 3 GPUs and a M.2 SSD. (M.2 SSD are even faster than SATA SSDs.)

I would also like to point out the improvement in OptiX code in Daz Studio 4.9 vs. 4.8. Whatever the programmers did over there at Daz, improved render times when using OptiX Acceleration. Let’s hope the trend continues. So, whether you love or hate Daz Connect, and/or the idea of encrypted products, you still might want to make the jump to 4.9 if you haven’t already.

Plus, Iray in Daz Studio 4.9 renders things a little bit differently. The biggest difference is in the way it handles scattering. Most likely, all the new content released from now on will be optimized for Daz Studio 4.9.

I hope you enjoyed this post, let me know in the comments below!! If you did, remember to share and like it, so other people can enjoy it too!