What's Your Longest Render?

[Spectralis]

I'm currently rendering an animation that's taking 60 hours. I've never rendered for such a long time but so far it's going well. I just wondered what your longest render has been? And what techniques you used to try to reduce the render time.

[linvanchene]

@ Render times

I just wondered what your longest render has been?

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My longest render with Octane was so far a scene combining fiber hair with a lot of reflective surfaces:

Total Number of triangles: 17'872'823.
31h 43 min for 4310 spix
VRAM used 4094MB.
Original Resolution: 7680x4320 Pixel.

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Kernel was always PMC.
Keep in mind that the renders probably could have been aborted at an earlier point without noticeable quality difference. I just let them run over night or when I am out of office for a few days...

Some more numbers I collected:

A scene with fiber hair and fog.
Note that even with "lower" 4k resolution it was enough to reach 2nd place.

Total number of triangles in the scene: 16'815'547.
24h+ min for 10'000spix
VRAM used: geometry 2330MB, textures 1971MB
Original Resolution: 3840x5760 Pixel.

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Fiber hair. A LOT of it.
Total Number of triangles in jungle girl character scene: 23'910'002.
21:27h for 3180spix
VRAM used: 4'576MB.
Original Resolution: 7680x4320 Pixel

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Total number of triangles in the scene: 25'949'727.
13h 1min for 3160 spix
VRAM used: geometry 4118MB, textures 993MB.
Original Resolution: 7680x4320 Pixel.

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Total Number of triangles in the scene: 1'935'170.
Render Time: 8h+ for 8275 spix at 6000x3375 with two Asus GTX Titan.

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Total Number of triangles in cat and background scene: 14'927'939.
7:05h for 3108 spix
VRAM used 3'234MB.
Original Resolution: 7680x4320 Pixel

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Kernel: PMC
Total Number of triangles in the scene: 529'027.
Render Time: 6h+ for 6225 spix at 6000x3375 with three Asus GTX Titan.

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Kernel: PMC
Total Number of triangles in the scene: 693896.
Render Time: 2h 30 minutes for 5008 spix at 6000x3375 with 3 GTX Titan.
Postproduction with Adobe Creative Cloud Applications

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And what techniques you used to try to reduce the render time.

- Throw money at the problem
The first thing to consider is using at least two GPU for rendering.
By adding a 2nd GPU render time is halved. From 100% down to 50%.
This is the best performance increase for money.

After that you get diminishing returns.
If you add a 3rd GPU you have the same cost for the additional card but now only get a smaller speed increase from 50% to 33%.

For the 4th card you would only get a speed increase from 33% to 25% but paid exactly the same amount for the card.

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Keep in mind that Otoy may sooner or later release the Cloud Edition.
Depending on the price model this might also be interesting to render animations for non commercial projects.

Until this happens we might need to look for more traditional solutions:

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- Reduced resolution.

For still images I went from 8k (7680x4320) to 4k (3840x2160)
The main point of rendering at 8k was to get an understanding how long render times would be. Rendering at 8k is only worth the time if you use very high detailed 3d models and textures.


For animations you might want to consider still rendering at 720p. (1280x720).

Currently rendering at 4K may only be an option for high profile promo projects to showcase new 4k monitors.
Full HD (1920x1080) may remain a standard for most commercial projects for some time.

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- Reduce frame number
Does it really need to be 30 frames per second?
In Europe 25fps is standard and not many people think visible quality is lost.

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- Split scene into different sub scenes

My impression is that for more stylised renders that are not trying to simulate a realistic light solution it might actually be faster to render out characters and background separately.

Example:
Render the background in PMC with a complex light setup to achieve a realistic light situation.
Render character with a lot of fiber hair with an HDR Environment that simulates a simular light situation than the background.

The main idea here is that a "realistic" light situation in most cases will cast very harsh shadows on faces. In real life photographers use flash lights, reflectors and diffusors.
You can simulate this in 3d with the help of props for realistic looking indirect light solutions in PMC.
But the faster solution is to simply use HDR Environments.

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- Use low quality assets for the background

If the background is going to be blurred anyway there is no point of using high detail geometry and textures for background objects.

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For animations

- Do not render backgrounds each frame


Rendering the background takes time.
If the character is moving around in front of a still background there is no point of rendering the background out each frame.
Only render the background out once.

In many cases you can "fake" an animated background by slowly moving one very high resolution background image in postproduction.
Use reflection maps to still have some kind of cool looking reflection on scene objects.

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To summarize this:

Save time by cheating in places that most people will not notice.

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[Spectralis]

Fantastic post linvanchene! Nearly 32 hrs rendering one image must be a record. The quality must've been excellent.

The one thing that's reduced render times for me has been to render out moving figures without the background and then compositing them all together. But I'd love to find a way to retain the scene lighting and shadows when rendering just the figures. I'm not too familiar with Carrara but I think this is possible to do with it but not with DS unfortunately.

I also often reduce textures for animations and render at 500 spix in HD @ 24fps which looks pretty good once composited using FX. As you say, bigger, better graphics cards are the best solution until it's possible to upload to the OTOY cloud. But while uploading a scene might be feasible, I imagine that downloading the huge animation renders would take forever without a very fast connection.

[larsmidnatt]

ah i remember the days of rendering with lux for like 5 days lol.

For octane I've had a couple of 12 hour renders, and one that was 16 hours. I was only using a 660ti at the time. Now I've got 2x the rendering speed so those same renders wouldn't have taken nearly as long. they were only 2000x3000 pixels or so. needed 4-6k samples and I would assume PMC mode. sorry can't remember what teh scene compositions were, but I know one of them wasn't super well lit, but that was a quality I wanted to keep so I just had to wait the samples out.

each time they were single character renders. with regular old mesh hair. It wasn't the geometry that was the issue, it was always shadows and occasionally a strange material that needed some time.

[Spectralis]

I've noticed that using Nerd3D's fog increases render times enormously as do certain other props and textures. And sometimes certain textures and props such as clothing or hair increase render times for reasons I can't figure out while others don't have the same effect. For example, this product,

http://www.daz3d.com/hitman

caused DAZ and OR on my system to slow down to a crawl but when I replaced this clothing with something else that used more resources everything went back to normal. Not sure why though?

[t_3]

caused DAZ and OR on my system to slow down to a crawl but when I replaced this clothing with something else that used more resources everything went back to normal. Not sure why though?

what you can do to track that down:

- switch the used materials one by one to color or hidden (in the mat tab)
... this way you can test what material needs most performance (by watching the ms/sec number increasing).

- if it seems to be none of the mats, of course the geometry is causing the slow-down;
... might have subd level set to high values?
... it could be simply that the geometry has issues that causes octane to slow down.

in case you find it could be a particular material, it would be interesting to investigate it; you can export it as .orbx (= with the maps included) and provide a download somewhere (dropbox, gdrive, etc.)

[Spectralis]

That's really useful info t_3. I'll try your suggestions. The more experience I have of the plugin and the more advice I get the easier it is to fine tune scenes and renders to get the highest quality renders using the least resources. Some of the threads about textures and lighting have given me a lot of help so thought I'd start one about rendering.

[sikotik13]

Of mild note: If one is not particularly attached to the materials being used in Daz Studio (as in, will use custom Octane Materials for everything on a particular object, like a shirt or pair of shoes), one can always apply a simple shader to said object. 1.) This speeds up auto-convert, as it is now auto-converting a plain white material, 2.) because there is no longer a material linked within Daz Studio to this surface, there is less VRAM/RAM in use, 3.) It eliminates the possibility of shader nodes being wonky causing slowdown (If I remember correctly, this was an issue with the Hitman outfit some time ago). It also occasionally helps with skins that may have issues, and I know I've run across a few of them that are... special. Also, if you want to keep the base diffuse and/or bump, switching to a simple shader (like Daz Default, or even better, omniFreaker's simpleSurface), can still reduce the actual memory footprint of the scene, even if using control+click to retain the maps, which tends to help with keeping Daz Studio as responsive as possible.

Just something I picked up back in 1.2 with the image count restrictions. I noticed a lot of the extra stuff in uberSurface and AoA's SSS seemed to eat memory, when none of it was really being used in OcDS. Swapping over to simpleSurface, retaining maps often gave me a noticable improvement in Daz Studio responsiveness, and for certain skins/materials (again, I fail to recall any specifically, sadly, but there were at least a few by several artists, especially Poser-based ones) even a bit of speed increase in render times for the same scene. It became my default thing to check if it seemed something simple was taking too long to render.