As a new user of this awesome engine I (and several others) could use some tips to improve (or reduce, depending on the POV) rendering time when using the IRay rendering engine.
The big drawback of this engine is that it takes huge, if not all, the GPUs computing capacity and it takes a lot of time to do all these calculations that result in the awesome pictures we like so much.

That much time doing the rendering is very frustrating because it we can't do much more when the computer is making the picture.

So any good tips to reduce that would be utterly welcomed.

Eclipse did give his insight on another thread - that I now migrate here - and I'd like to keep discussing it here. Also, any other tips are also welcomed.

I'll cite his tip:

"Pretty simple, but rather time consuming to get right: Iray Section Planes EVERYWHERE. They determine what the render engine is going to bother calculating and what it will ignore. Gotta be careful with placements as you want to retain as much geometry as possible for the shadows/indirect lighting though (especially for a lot of indoor scenes). If i remove the section planes from my scenes the render time can increase by 100%+ sometimes. Usually unbiased renderers like Iray support "light portals" that define areas where light paths are calculated (which GREATLY improves render times), but those aren't supported in Daz yet sadly, boo.

Other than that it's some minor material tweaking. Materials like skin are quite demanding and often you don't even need to simulate subsurface scattering to get good results if characters are further away. SSS on the lady in my "Cryo" render has a noticeable hit on render time so i didn't even bother using it and you can barely tell the difference. I could go into further detail about other things, but section planes are honestly the real key."

I haven't tried this yet - because my computer is totally occupied rendering something with IRAy but I wonder if these Section Planes don't interfere with ambient lighting.
Since IRay emulates real physics lighting, putting a plane somewhere in the scene, even if away the camera shot, wouldn't it block any light that bounces around the room, and change the ambient light you desire for your scene?

Oh hey Morrtze! Just came to make the thread when i saw you already did it

You are absolutely right about the ambient/indirect light! Depending on how complex your scene is, properly setting up section nodes can be more time consuming than the actual render. In indoor scenes where you want all the nice ambient light that is reflecting off walls and other objects it will most likely not be something you want to do. In outdoor scenes you have a lot more freedom and can generally go completely nuts with them, cutting off up to 90% of the scene's geometry without noticing any lighting difference in the render.

With some experience though, it is possible to make indoor lighting look right even if half the room behind the camera is infact not there Atleast if the back of the room you are removing doesnt have any big light sources.

Another solution for indoor scenes is to simply use a HDR enviroment map that closely resembles the light atmosphere you're aiming for. Finding a nice free HDR map that happens to fit can be tough though. Evenso i personally still believe just messing with section nodes is the best thing to do even in most of indoor scenes, but it's worth keeping an eye out for nice HDR maps. I'll share an example of a indoor scene i did:



In this render, there is literally NO geometry outside of direct camera view. There is no lighting being bounced off walls and entering the scene. Instead, i actually used a HDR map to handle the light. Despite that the results are still pretty nice and compared to the full scene render, i have saved 90% on render time! This one took 20 minutes compared to nearly twice that if i had not used section nodes. Keep in mind render times will vary immensely depending on your scene. Section nodes are not a miracle cure by any stretch, but they can help a lot. Resolution exponentially increases render times for example and material complexity can be rough too.

Lastly; Hardware. I'm on a lowly 680GTX right now. More powerful Nvidia cards will ofcourse get much faster results. If you are upgrading, aim for as many CUDA cores on the card as you can get.

Great tips there.

Yeah, and HDR map greatly enhances rendering time, and lightens up yhe whole scene. But I don't like that kind of lighting method for indoors, specially at night.
When you search for realism for indoors lit scenes you look for strong contrasts between a hard light coming from the object that iluminates (a lamp, a TV, a candle), strong shadows, and very midly middles. HDR isn't the best solution for those contrasts and surely isn't when you have the light source in your camera shot.

I'm rendering this scene, in a bar, at night, where there are a lot of iluminations, with ceiling lamps and a candle in the table. Add some transparency from glasses and the candle glass, jewellery reflection, liquid transparency and refraction, and you got a heavy scene to render. I've deleted everything from the scene save from the lights and what's in the camera shot. Still, I have to render at 1h+ and still stop it at 4000 iterations.

My GTX 970 and GTX980Ti do their max to help me but there is no way to avoid that complex scenes take Tons of time with IRay. We'll hope that in a year from now 2 GTX 1080Ti will help though

I don't know where I could put those Section nodes in my scene. I need the light that comes from the opposite corner of the room.

Mortze wrote:I'm rendering this scene, in a bar, at night, where there are a lot of iluminations, with ceiling lamps and a candle in the table. Add some transparency from glasses and the candle glass, jewellery reflection, liquid transparency and refraction, and you got a heavy scene to render. I've deleted everything from the scene save from the lights and what's in the camera shot. Still, I have to render at 1h+ and still stop it at 4000 iterations.

I don't know where I could put those Section nodes in my scene. I need the light that comes from the opposite corner of the room.

Yeah, your scene sounds like a no-go for section nodes. Indoor scenes with many light sources will always be hell to deal with. In regards to HDR maps though, you can definitely get great results, aslong as you pick the right one and go with the right settings. The right combination of section nodes and HDRs can get you some incredible results with very low rendering times. It's always worth googling around for a bit to look for an HDR that fits your enviroment. Sometimes spending ages to render 100% accurate scene lighting isnt worth it when cheating like crazy looks just as good at a fraction of the render time

The perfect section node scenario is a large-scale outdoor sceene with lots of complex materials like water or metal. For example, in a beach scene you could cut off literally everything outside of view and there would be 0 visual difference, but render times would be greatly improved due to a significantly lowered amount of water. Or it could be a big forest scene where foliage might be using subsurface scattering, you could cut off everything above and on the sides, and substitute it with a forest HDR if necessary.

Eclipse wrote:The perfect section node scenario is a large-scale outdoor sceene with lots of complex materials like water or metal. For example, in a beach scene you could cut off literally everything outside of view and there would be 0 visual difference, but render times would be greatly improved due to a significantly lowered amount of water. Or it could be a big forest scene where foliage might be using subsurface scattering, you could cut off everything above and on the sides, and substitute it with a forest HDR if necessary.

Are you saying that, in the example of a beach scene, if my camera angle captures the character having a good time in the water, and I place section nodes on the right and left of the camera it won't make any difference?
How about you give us an example of the node sections placement on a quick scene, from the Viewpoint POV. Like and aerial printscreen.
I'm still not sure how that works without influencing the ambient light. In a HDR lighted scene, where light comes literally from everywhere because it's emited by the HDR sphere a node section would block the light coming in straight line from on direction, no?

Mortze wrote:Are you saying that, in the example of a beach scene, if my camera angle captures the character having a good time in the water, and I place section nodes on the right and left of the camera it won't make any difference?
How about you give us an example of the node sections placement on a quick scene, from the Viewpoint POV. Like and aerial printscreen.
I'm still not sure how that works without influencing the ambient light. In a HDR lighted scene, where light comes literally from everywhere because it's emited by the HDR sphere a node section would block the light coming in straight line from on direction, no?

The HDR enviroment map is not considered as an object/geometry, so it will be ignored by the section nodes. Light from the HDR will interact with the things in your render as usual, no matter where you have put section nodes. Depending on the scene, you might have to move some lights around to get the same light result as before you put down section nodes. In a water scene there should in theory be no lighting difference by cutting off water though.

Threw 3 pictures together super quick just to show the difference. This scene consists of a pretty big lava enviroment (with all lava acting as a light source) which i cut off significantly with section nodes. Please ignore the fact it looks terrible as we only care about the overall lighting here which should be clear enough.

In this image there are no section nodes. The entire scene is complete and unaltered:


In the following picture i have cut off pretty much everything. Render time is much faster, and the lighting is for all intents and purposes the same:


There is a difference in lighting coming from the right because the section node is super close and cuts off some ground that would normally block some light from lava, but that could be easily corrected if you wanted to retain the exact same lighting result as before. Overall, the difference (which you could fix by moving the section node on the right slightly more) is negligible and definitely not worth the extra render time.

Here is a overview of the scene where you can see the pizza-slice that i did of the scene.


I hope i explained that reasonably.
Just for good measure here is the final version which didn't turn out great, but that's besides the point :

Eclipse wrote:The HDR enviroment map is not considered as an object/geometry, so it will be ignored by the section nodes. Light from the HDR will interact with the things in your render as usual, no matter where you have put section nodes.

Ah, that changes everything. Now I understand

I'll have a few outdoor scenes to do and I'll definitly try that. I'll use an HDR for lighting so that should work. I'll try with and without the nodes to compare.

But for indoors I'm afraid that no HDR can compare to more traditional lighting, like spotlights, point lights, and emissive lights.

Eclipse wrote:Just for good measure here is the final version which didn't turn out great, but that's besides the point :

Beg to differ. It's quite a nice picture. Apply some Photoshop mojo to it and you got yourself a really cool picture.
That supposed to be a phaser or a laser?

Mortze wrote:That supposed to be a phaser or a laser?

Was going for some kind of beam/lance cannon. Originally wanted to have it light up more of the scene but had a tough time getting it to work well with the volumetric fog so it ended up a little on the boring side. Gotta hate it when you wait on a render for 40 minutes just to discover the damn thing doesnt look right at all. Said "fuck it" and did something else instead lol.

Eclipse wrote:Was going for some kind of beam/lance cannon. Originally wanted to have it light up more of the scene but had a tough time getting it to work well with the volumetric fog so it ended up a little on the boring side. Gotta hate it when you wait on a render for 40 minutes just to discover the damn thing doesnt look right at all. Said "fuck it" and did something else instead lol.

Volumetric fog?
Try something simpler. If you go for a phaser (totally diferent from a laser but the same technique applies), create a cilinder primitive. Scale it to be your phaser beam. Put an emissive shader on it. Set the parameters for color, choose a high temperature and Lumex.
Then on the Render Settings, go to Filtering, Bloom Filter ON, and play with the Pixel Filter Radius to get that bloom effect.
You can monitor those testings with the IRay preview view.

For a laser it's the same thing but a smaller cylinder, and also some Motion Blur in Photoshop.

Mortze wrote:Volumetric fog?
Try something simpler. If you go for a phaser (totally diferent from a laser but the same technique applies), create a cilinder primitive. Scale it to be your phaser beam. Put an emissive shader on it. Set the parameters for color, choose a high temperature and Lumex.
Then on the Render Settings, go to Filtering, Bloom Filter ON, and play with the Pixel Filter Radius to get that bloom effect.
You can monitor those testings with the IRay preview view.

For a laser it's the same thing but a smaller cylinder, and also some Motion Blur in Photoshop.

That is literally exactly what i did haha
The entire scene is actually in a sphere with a SSS shader on it to simulate atmospheric depth. You can see how stuff in the background is faded out as if you're looking through a mist. Just a slight effect in this case as i was just trying it out.

Keep showing us what you do.

Interessing tips. On my "old" computer, take ages to render.

Apparantly it can help to make less samples, but twice the output size.
I haven't tested it though, but link is here : http://buerobewegt.com/quicktip-rendering-even-faster-in-iray/

I just upgraded from a GTX 970 to 1080.

I had a half done scene, that I decided to compare render times with.
All is done without OptiX optimization - 3282 iterations.

With 970 + Daz (released 4.9 version): 1952 secs.
With 970 + Daz (Public Beta version): 1689 secs.
With 1080 + Daz (Public Beta version): 1321 secs.

Oooh, Mortze, the Daz Public Beta not only supports 1080 cards, but speeds up your existing cards....

Tlaero