How can i improve my IRAY render only using CPU

gvinicius98

Hello, i am having a render issue, this is my setup:

CPU: AMD RYZEN 5600X

GPU: Amd R7 240

RAM: 3600Mhz 16gb Geil Orion

Mobo: Asrock 550m Pro4

I know, my GPU sucks, but it's what i have now, and due to quaretine i can't buy a new one, so i was thinking if i can improve my render speed with IRAY using only my CPU, right now it's taking a long time (40 minutes) to render a scecne with good ilumination, my render setting are:

Pixel Size: 1920x1080

Auto Headlamp: Never

Max Samples: 7500

Render Quality: 2

Rendering Converged Ratio: 98%

I was thinking if i can get any tips on how to improve my renders, or if it's possible with only my CPU, i don't want to use 3Delight cause it reduce a lot the render quality, thank u!!

Gordig

Are you talking about improving the quality of your renders, or the speed?

ebergerly

First, I think your AMD GPU isn't supported with Iray, so there's not much you can do.

Second, IMO the best way to make drastic improvements in render time is to minimize your scenes as much as possible. The first thing is to not be rendering inside an enclosed space (like a room with 4 walls, a floor and ceiling). That's deadly to render times. What I do is to "imply" the scene, and maybe just use a blank background and place some props that give a good idea of what the location is. So a single figure with a blank background will render fast (Environment tab, Type = Background, and choose a background color). And if you want to simulate the nice illumination you get from an environment like a room or outdoors, try using an HDR image. 

The next step after that is to learn how to composite (ie, put multiple image layers together into a single image), but that's a whole 'nother world of stuff. 

gvinicius98

Gordig said:

Are you talking about improving the quality of your renders, or the speed?

The speed, i'm fine with the quality, i just don't want to use 3Delight

gvinicius98

ebergerly said:

First, I think your AMD GPU isn't supported with Iray, so there's not much you can do.

Second, IMO the best way to make drastic improvements in render time is to minimize your scenes as much as possible. The first thing is to not be rendering inside an enclosed space (like a room with 4 walls, a floor and ceiling). That's deadly to render times. What I do is to "imply" the scene, and maybe just use a blank background and place some props that give a good idea of what the location is. So a single figure with a blank background will render fast (Environment tab, Type = Background, and choose a background color). And if you want to simulate the nice illumination you get from an environment like a room or outdoors, try using an HDR image. 

The next step after that is to learn how to composite (ie, put multiple image layers together into a single image), but that's a whole 'nother world of stuff. 

Thanks for the reply, but the whole point is to be able to use Iray, cause i don't like the result using 3Delight, i need realistic lighting, i will try these changes to see if changes something 

JVRenderer

gvinicius98 said:

Thanks for the reply, but the whole point is to be able to use Iray, cause i don't like the result using 3Delight, i need realistic lighting, i will try these changes to see if changes something 

Realistic lighting (quality) in Iray requires a lot of resources, notably a good GPU.  Your AMD CPU can generated quality Iray renders at the cost of speed.  Renders will require upward of 4+ hours or even days, depending on scene complexity.  If you want the speed, (without hardware improvements) you will need to sacrifice on quality.

Paintbox

I would actually try to export to Blender if I had CPU only, more options in Blender probably. I think you can render in Cycles with AMD GPU. (Not 100% sure)

ebergerly

Yeah, if you're unwilling to buy even a low end NVIDIA-based GPU you're out of luck with regards to Iray on the AMD GPU. You can do Iray using your CPU, and it will be a lot slower, but as I said there are ways to get high quality Iray renders using your CPU that won't take forever. It depends on YOUR goals for your images, not somebody else's. 

For example, if you're willing to have a photo as a background, for example, you can render a character with a transparent background in Iray, lit by an HDR image, and then bring that into a compositing program and put the character over the photo. You can also apply depth of field effects, change the lighting and the colors, add shadows, and on and on. And depending on your skill level you can get some excellent results. 

Or if you're willing to have a blurred background that's quick and easy in a compositing software. And you can do it in real time, compared to just about any GPU which is going to take time doing fancy effects, and often with (IMO) crummy results.

But it all depends on what you want and need. 

ebergerly

Here's an example...

I grabbed a basic G3 character, threw some standard clothes on it and threw it into a scene, grabbed an 8k HDRI backround image, disabled my GPU's so only my Ryzen 7-1700 was rendering, and the image finished in 3 minutes and 10 seconds. Yes, that's 3 minutes, not 3 hours.

Now I spent zero time on it, the lighting/shadows are wrong, but the point is that with a bit of time and the right approach you can get stuff that looks at least reasonable without spending 3 decades doing a render. And if that's all you want, then a CPU is fine. 

Just imagine what you could do with a little preparation and a bit of skill...

onix

The only way to use CPU rendering is if you reduce required rendering iterations significantly so no dreaming about 98% convergence you should be happy with 50% as the near-ideal result. 

Sure picture will be quite grainy which can be fixed by using some AI denoiser. not exactly sure how it would work better but I suspect that Ai denoiser will do better work if you apply it to higher resolution pictures then downscale it because when you use denoiser the issue is not the picture being noisy but the fact that your picture is lacking detail.

Another way to speed up rendering is to ensure that everything in your scene received direct illumination from the light source. Unfortunately, this reduces picture realism and makes it quite flat not really that much different from 3delight but rendering speed becomes way better.

if you rely on bounced light illumination you slow down rendering many times

 

 

 

 

ebergerly

Here's a CPU-only render in Iray that took only 2 minutes, 30 seconds. 

And it also took about that long to set it up from scratch. 

WendyLuvsCatz

for what it is worth, I have had to use my more powerful CPU rig to render scenes that won't fit on my rig with the Nvidia card anyway, If I have to I generally do render them very big then denoise them in Gimp and scale them down if needed.

I do 360 smaller blurry spherical renders of the scene if that happens as I do animations then use those as environment dome textures for my characters with a rendered matching background.

onix

ebergerly said:

Here's a CPU-only render in Iray that took only 2 minutes, 30 seconds. 

And it also took about that long to set it up from scratch. 

This is not that relevant, because if you are using HDRI background rendering speed will mostly depend on how much percentage of the screen takes your figure.

 

 

ebergerly

Obviously, if you change your scene (and this applies to either CPU rendering or GPU rendering) it can take longer to render.

And by the way, that was 95% convergence, not 50%.

TBorNot

You're probably stuck anyway, NVidia cards are pretty scarce these days.