In this tutorial I’ll explain some things you can do sto help optimize your scenes for iray. I believe these tips are standard fare for many of the GPU rendering applications. Read on for the details.For this “tutorial” I will be using an architectural test scene created by Mark Galbraith in a thread at the Vizdepot (thanks).
Upon starting with iray you may be tempted to simply load some of your mental ray scenes in iray and hit the make pretty button. That may work, provided you didn’t use shaders, materials, or features not supported by iray. However you may be able to make some adjustments to your mental ray scenes in order to get less noise in your iray renders.
First tip: Direct light + no glass = less noise. What that means is that a scene with light sources outside the windows and no glass in the windows will produce less noise within the same render time as a scene with visible glass and lit by the environment.
In this render the scene is lit by the scene environment (mr Physical Sky) without any portal lights outside the windows and the window glass is visible:
This is the same scene with the window glass hidden:
While the scene with glass is more realistic in that the glass provides that subtle green/blue tint as you’d expect to see, it also needs more time to clear noise than the non-visible glass version. The non-visible glass version is also brighter, but again that’s to be expected since the glass had a subtle tint to it. I could have easily adjusted the exposure to make the glass version brighter…or rendered out to HDR/EXR format and adjusted the exposure “real-time” in post.
Up next I placed portal lights outside the windows (4 of them) and configured them to be visible and use a color instead of the scene environment. Here’s the visible window glass version:
And here’s the version with the window glass hidden:
You’ll notice a big difference in these from both the visible glass and hidden glass renders and the environment lit versions from earlier. There’s far less noise in the non-visible glass, visible portal lights outside windows version. So, if you can get by with hiding the window glass in your scenes you may find placing lights outside the windows of your interior scenes provides quicker renders by eliminating noise faster.
Next, since self-illuminated objects work so well in iray I wanted to see if there was any difference between lighting a scene with a photometric light vs. self-illuminated geometry. Here’s the scene lit with a single photometric light source:
And the same scene without any light sources, and illuminated by a 3″ piece of geometry with a self-illuminated material applied:
I was a bit surprised by this one. I thought there would be more noise in the self-illuminated material version, but they are fairly similar in terms of noise/grain! So, it seems there’s not a lot of extra noise/grain when using self-illuminated geometry.
All the renders used in this blog entry were set to use the same amount of time, 15 minutes with a full resolution of 1920 x 1080 using a Quadro5000 + i7 960 CPU. Since scaling the images down reduces the noise I have uploaded the full resolution images HERE for easier comparison.
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Nice post, i dont have iray but all of this is very interesting though. I think you should try setting the photometric light with the sphere shape, or if you did, the geomtery based one its more yellowish.
looking forward to more tests.
thanks jeff
Excellent tip on the glass, I had not tried a scene without.
Jeff, I’m having trouble with a scene using the mr. sun/mr. sky lights. They do not render out. my scene shows no sun light. the interior lights work fine, but I have nothing coming in from the outside environment.
Thanks
Thanks Jeff…
You’re showing the new way for us as you did some years ago with the new Mental Ray at that time…
Josh – Sounds like something is blocking the windows. Could be the portal lights if they are configured incorrectly. Take a look at this file for reference on the settings: DOWNLOAD FILE
thanks jeff, very very helpful.. I think, in the near future Iray will simplify rendering work flow and I really don’t know if I should be happy or worried!
You’re not alone, I think a lot of us have the same mixed feelings about the implications these applications will have on our future.
Hi Jeff, Thanks for your dedication to help the CGI community grow interest in HQ-3D!
I am struggling against the noise and fireflies produced by iRay in interior scenes! I`ve let a scene render for 10 hrs. on a dual xeon x5680 and I couldn`t get rid of the noise.
I`ve downladed the high res images of your interiors and they have noise and fireflies too.
I am trying extreme exposures and extreme luminance sttings and it doesn`t help.
Do you have any hints of how to eliminate them?
Is iRay simply not ripe for interior lightning?
Your opinion is kindly appreciated.
best regards,
Francisco
To reduce the noise/fireflies you can:
1. Let it render longer.
2. Render larger than what you need and then reduce the image size.
3. Try to remove the grain/fireflies in post. Some say this application works well, but I haven’t tried it: http://www.visnevskis.com/defly/
I would expect grain in the images I rendered for this article as they were only 15 minute renders. If I wanted grain free images I would need to let them render longer. How long depends on the scene.
iRay is similar to rendering with mental ray or any other engine in that interior scenes typically require longer calculation times than exterior daylight scenes where there’s far more light to work with and that light doesn’t have to bounce around in a confined space.
Caustics and/or highly reflective/glossy materials will also require more time to clear, especially in interior scenes. Doing things like hiding window glass may help reduce caustic fireflies.
How the scene is illuminated also matters. For example, notice how the night version of my scene has more noise than the day version. The day version provides more light sources than the single, small light source in the night version. Scenes illuminated with small, bright light sources will require more time to clear noise than those with large open windows or other large light sources.
Is iRay ready for interior lighting? It works well for some situations (rooms with lot’s of windows and/or large light sources) and not so well in others (Church of light would probably take a while to clear).
Of course our hardware plays a big role on how efficient iRay is as well. At the rate that hardware evolves I would imagine it won’t be too long before these tough to render scenarios will become far more manageable.
Completely agree – Iray is just amazing in external situations but is leaving me underwhelmed indoors. Night-time internal scenes lit by a few spotlights seem to be Iray’s achille’s heel.
Nothing a 6 gig 2000 cuda core card couldn’t sort out though.
C’mon Nvidea, sort it out.
thanks jeff, very very helpful.. I think, in the near future Iray will simplify rendering work flow and I really don’t know if I should be happy or worried!
Excellent tip on the glass, I had not tried a scene without.
Hello Jeff! Thanks for your useful posts.I’ve seen on Area that a guy was complaining about long render times using iRay.I have the same problem
I have a similar system like you used for this scene(quadro 5000+ I 7 2600K ). I’ve downloaded now this scene and I’m curios whether I will have a similar render time (15 minutes)
Like you said it’s possible that I have false expectations.
Hi again! I’ve made the test with this scene and I have the same result as you.I’ve also tried a similar scene,but with furniture in it and it took 2 and a half hours with visible glass and environmental background.(i will also try without glass)A heavier interior scene I guess it will take about 3-4 hours.That means to get a render time within an hour I will have to purchase a Tesla C2050 at least.
One more question if you have the time,why my backgrounds using iRay are blurry? In my material editor the blur is set to default value.(it’s a normal jpg image and not HDRI)
Yeah, interiors will typically require more calculation time than exteriors or product-vis, automotive renders, etc..
Backgrounds are blurry because I think the blur environment option is enabled by default with iray, plus I think iray defaults to 2048×1024 res for the environment too.
You can manually adjust those with scripts like the iray manager scripts that are available. I’ve provided links to those in most of my blog entries…except for this one of course. If you don’t want to dig through those then Google “iray manager script” and you should find the links.
Keep in mind that if you manually change to a higher resolution environment map it’ll use more memory for that than the default settings.
Hello Jeff!
I’m getting use to iRay more and more.Because the interiors are quite time consuming I would like to invest in new GPUs to speed up the process.(right now I have CPU 2600K GPU quadroo 5000 ; a heavier int. scene renders in 6hours)Could you give me an advice which would be my best choice.I want fast renders for interiors (less then an hour) but also enough memory for bigger exterior scenes and ext. walk trough animation.( with HQ grass,trees,bushes etc).
I though of a Quadro 6000, maybe 2. (2 might be an exaggeration,I don’t know…)
I would appreciate an advice if you have time for this.
Thanks in advance!
Hi Jeff!
I’ve seen your blog about iRay and GPU FAQ.
I realized that a load of money have to be spent if you have big,detailed scenes.Some of my scenes easily exceed the memory of my Quadro 5000 GPU.
Now I’ve ordered a Quadro Plex 7000 to solve this memory problem. I know it’s a lot of money,but the company I’m working for bought it for me,because they want fast and realistic renders. For speed I could have 4-5 Quadro 6000,but then there’s the memory issue again. I’m curios what result I will have.It might turn out that more quadro 6000 GPUs would have been a better solution.
I hope that iRay will have more options in the next edition.
Waiting for new blogs…
Sounds like the Quadro Plex 7000 is two 6GB GPUs mated together. However it does have more CUDA cores (512 x 2 = 1024) than if you were to buy two Tesla 2070 gpus (448 x 2 = 896). So it should render faster than two Tesla GPUs, but I think the memory for the scenes will still be limited to 6GB per GPU (similar to the dual GPU 590 GTX type cards). If you find that I’m wrong in that assumption and it does combine the memory for a full 12gb, please let me know.
Price wise, I’m not sure how much a Quadro Plex 7000 costs, but two Tesla 2070′s would run about $5000.00 (USD).
Hi sir! thank you very much for this. I’m having a problem at my scene. My scene consists of a building with an HDRI env map. I’m using portal lights at the windows. The portal light color source is env HDRI. the problem is my on multiplier of portal light is not working. no matter it’s 1000 or 1 it’s givinf same amount of light. the only way to increase the light coming from exterior to interior is to change the output rgb lvl of HDRI. but with this the outside environment is also overexposed. i tried to turn on visibility of the portal lights and the transparency color to 50% grey. but it’s not working with iray. seems like it’s just ignoring the existance of portal light. i checked the same scene with mental ray. portal works fine there.
I also checked the scene you provided. it seems the portal lights are also not working if the color source is the env HDRI.
really need a bit help!