Layering Characters / Set - Render Times

[CGMas]

Hi everyone,

I've got a question for you ^^ !

Currently I'm trying to render and optimize an interior scene.
For the lighting I'm using a dome light and one rectangle light by window to reduce the indirect illumination and add some direct lighting.
I know lighting interior with domelight is not as fast as sunlight but I didn't manage to reproduce the same things with the sun.
The GI is set to default Brute Force Light Cache.

In my scene I've got 2 main characters at the center of the frame and 4 secondaries behind.
They've got yeti hair and fur.

My tests render are done in 512x270
The thing is if I render a frame with the characters and the set, it takes 23 min to render.
Maybe it's too long, I'm not sure but that's not the point.

If I render the set without the characters (all purely hidden, the fur too), it takes 9 min to render.
If I render the scene with the characters but without their material and fur, just in basic lambert material, it's faster ! It takes 7 min to render !?
If I render the scene with the characters in camera visibility off and the fur hidden, it takes 14 min to render !

All those tests are done in low resolution as I'll have to render the scene in 2K...

Is it a normal behavior ?
Is there something I'm missing ?
Is it normal that a scene with less assets, less materials takes longer than a scene with more assets (but in grey basic material) ?
Is it normal that when I'm turning off camera visibility it takes more time to render ?

Thank you for your time and your answers !
^^

Max

[yolov]

It's a bit hard to tell without the scene, but here's my thoughts:
it is more or less expected for the render to be longer when the characters are not directly visibly to the camera compared to the basic lamber render, because they are just not directly visible, but they still have their shaders assigned and still contribute to GI and they are reflected in any reflective materials around the scene. The statistics at the end of the render in Maya's output window could give you a clue to why that's happening - there's stats on rays traced per ray type + num triangles, etc.
What exactly are you after with those setups?

[CGMas]

I forgot to tell that for the 14 min render with characters in camera visibility off they also got the lambert material.

Here the 14 min render stats (Characters with lambert and camera visibility off):

[2017/Feb/15|17:14:12] V-Ray: Number of raycasts: 527074284 (3812.75 per pixel)
[2017/Feb/15|17:14:12] V-Ray: Camera rays: 22271237 (161.11 per pixel)
[2017/Feb/15|17:14:12] V-Ray: Shadow rays: 359836551 (2602.98 per pixel)
[2017/Feb/15|17:14:12] V-Ray: GI rays: 124430687 (900.11 per pixel)
[2017/Feb/15|17:14:12] V-Ray: Reflection rays: 21215950 (153.47 per pixel)
[2017/Feb/15|17:14:12] V-Ray: Refraction rays: 0 (0.00 per pixel)
[2017/Feb/15|17:14:12] V-Ray: Unshaded rays: 13360760 (96.65 per pixel)
[2017/Feb/15|17:14:12] V-Ray: Light cache utilization: 51.59%
[2017/Feb/15|17:14:12] V-Ray: Premultiplied light cache utilization: 82.84%
[2017/Feb/15|17:14:12] V-Ray: Number of light evaluations: 342011438 (2474.04 per pixel)
[2017/Feb/15|17:14:13] V-Ray: Number of intersectable primitives: 1726185
[2017/Feb/15|17:14:13] V-Ray: SD triangles: 1726184
[2017/Feb/15|17:14:13] V-Ray: MB triangles: 0
[2017/Feb/15|17:14:13] V-Ray: Static primitives: 0
[2017/Feb/15|17:14:13] V-Ray: Moving primitives: 0
[2017/Feb/15|17:14:13] V-Ray: Infinite primitives: 1
[2017/Feb/15|17:14:13] V-Ray: Static hair segments: 0
[2017/Feb/15|17:14:13] V-Ray: Moving hair segments: 0
[2017/Feb/15|17:14:13] V-Ray: Total frame time 0h 14m 13.1s (853.1 s)

The 7 min render (7 min in VFB, but 8 in output window; characters visible with lambert material):

[2017/Feb/15|15:56:49] V-Ray: Number of raycasts: 369286635 (2671.34 per pixel)
[2017/Feb/15|15:56:49] V-Ray: Camera rays: 20663030 (149.47 per pixel)
[2017/Feb/15|15:56:49] V-Ray: Shadow rays: 275237756 (1991.01 per pixel)
[2017/Feb/15|15:56:49] V-Ray: GI rays: 102787512 (743.54 per pixel)
[2017/Feb/15|15:56:49] V-Ray: Reflection rays: 13745780 (99.43 per pixel)
[2017/Feb/15|15:56:49] V-Ray: Refraction rays: 0 (0.00 per pixel)
[2017/Feb/15|15:56:49] V-Ray: Unshaded rays: 13940728 (100.84 per pixel)
[2017/Feb/15|15:56:49] V-Ray: Light cache utilization: 53.79%
[2017/Feb/15|15:56:49] V-Ray: Premultiplied light cache utilization: 87.38%
[2017/Feb/15|15:56:49] V-Ray: Number of light evaluations: 279524646 (2022.02 per pixel)
[2017/Feb/15|15:56:50] V-Ray: Number of intersectable primitives: 1716361
[2017/Feb/15|15:56:50] V-Ray: SD triangles: 1716360
[2017/Feb/15|15:56:50] V-Ray: MB triangles: 0
[2017/Feb/15|15:56:50] V-Ray: Static primitives: 0
[2017/Feb/15|15:56:50] V-Ray: Moving primitives: 0
[2017/Feb/15|15:56:50] V-Ray: Infinite primitives: 1
[2017/Feb/15|15:56:50] V-Ray: Static hair segments: 0
[2017/Feb/15|15:56:50] V-Ray: Moving hair segments: 0
[2017/Feb/15|15:56:50] V-Ray: Total frame time 0h 8m 13.7s (493.7 s)

The 9 min render (set only):

[2017/Feb/15|15:22:38] V-Ray: Number of raycasts: 424162876 (3068.31 per pixel)
[2017/Feb/15|15:22:38] V-Ray: Camera rays: 20610518 (149.09 per pixel)
[2017/Feb/15|15:22:38] V-Ray: Shadow rays: 319555788 (2311.60 per pixel)
[2017/Feb/15|15:22:38] V-Ray: GI rays: 102450666 (741.11 per pixel)
[2017/Feb/15|15:22:38] V-Ray: Reflection rays: 19945676 (144.28 per pixel)
[2017/Feb/15|15:22:38] V-Ray: Refraction rays: 0 (0.00 per pixel)
[2017/Feb/15|15:22:38] V-Ray: Unshaded rays: 11131816 (80.53 per pixel)
[2017/Feb/15|15:22:38] V-Ray: Light cache utilization: 74.85%
[2017/Feb/15|15:22:38] V-Ray: Premultiplied light cache utilization: 92.90%
[2017/Feb/15|15:22:38] V-Ray: Number of light evaluations: 279565296 (2022.32 per pixel)
[2017/Feb/15|15:22:38] V-Ray: Number of intersectable primitives: 1170938
[2017/Feb/15|15:22:38] V-Ray: SD triangles: 1170937
[2017/Feb/15|15:22:38] V-Ray: MB triangles: 0
[2017/Feb/15|15:22:38] V-Ray: Static primitives: 0
[2017/Feb/15|15:22:38] V-Ray: Moving primitives: 0
[2017/Feb/15|15:22:38] V-Ray: Infinite primitives: 1
[2017/Feb/15|15:22:38] V-Ray: Static hair segments: 0
[2017/Feb/15|15:22:38] V-Ray: Moving hair segments: 0
[2017/Feb/15|15:22:39] V-Ray: Total frame time 0h 9m 17.6s (557.6 s)

And the 23/26 min (VFB/OutputWindow)(characters visible with hair, fur and materials):
[2017/Feb/15|14:04:07] V-Ray: Number of raycasts: 1004082405 (7263.33 per pixel)
[2017/Feb/15|14:04:07] V-Ray: Camera rays: 21996240 (159.12 per pixel)
[2017/Feb/15|14:04:07] V-Ray: Shadow rays: 808760670 (5850.41 per pixel)
[2017/Feb/15|14:04:07] V-Ray: GI rays: 623891470 (4513.10 per pixel)
[2017/Feb/15|14:04:07] V-Ray: Reflection rays: 18537991 (134.10 per pixel)
[2017/Feb/15|14:04:07] V-Ray: Refraction rays: 93951 (0.68 per pixel)
[2017/Feb/15|14:04:07] V-Ray: Unshaded rays: 39058562 (282.54 per pixel)
[2017/Feb/15|14:04:07] V-Ray: Light cache utilization: 10.41%
[2017/Feb/15|14:04:07] V-Ray: Premultiplied light cache utilization: 36.67%
[2017/Feb/15|14:04:07] V-Ray: Number of light evaluations: 807740185 (5843.03 per pixel)
[2017/Feb/15|14:04:08] V-Ray: Number of intersectable primitives: 1716361
[2017/Feb/15|14:04:08] V-Ray: SD triangles: 1716360
[2017/Feb/15|14:04:08] V-Ray: MB triangles: 0
[2017/Feb/15|14:04:08] V-Ray: Static primitives: 0
[2017/Feb/15|14:04:08] V-Ray: Moving primitives: 0
[2017/Feb/15|14:04:08] V-Ray: Infinite primitives: 1
[2017/Feb/15|14:04:08] V-Ray: Static hair segments: 16554201
[2017/Feb/15|14:04:08] V-Ray: Moving hair segments: 0
[2017/Feb/15|14:04:15] V-Ray: Total frame time 0h 28m 5.6s (1685.6 s)

I think the render of my set takes longer cause vray is rendering more materials (from the set) with reflections...

What I'm after with those setups is to find a way to properly render set and characters separately.
The problem is that I can render my scene with set and characters all together but when I separate my scene in layers, my render time increase way too much and often use the full RAM and even don't render after 12 hours....

[yolov]

Looking at the stats it kind of explains the render times - lower render times come with less raycasts.
In any case, if you know for certain a scenario where your scene uses too much RAM, we could take a look and try to figure out what happens.

[CGMas]

I've sent an email to support with images and render settings.
The scene is too complex to be sent...

Now a lot of my renders hungs at 20 or 30% with the RAM full but no processor activity at all ...

[yolov]

If too complex means too large, we can provide you ftp access or you can upload to any cloud drive and share a link.
Do you have a lot of subdivided or displaced (or both) objects in your scene?
Can you try switching off displacement globally and see if that helps? If it doesn't - you can try the same with subdivision. The option can be found in render settings > overrides > geometry.
What's your setting for dynamic memory limit? It's in render settings > settings > system.
You can try increasing that or set it to 0.
You can also try disabling embree (again from settings > system).
It's a bit hard to judge without the scene, but tomorrow I'll look at the images you've sent.

[CGMas]

The complexity of the scene is that it requires a lot of external files (alembic, fur, maps...).
So it would be a lot of work to get all the needed files from our network into a zippable folder and check that everything is good etc...

I think nearly every object is subdivided at 2 (vray max subdiv).
The default displacement subdision is set to 4.
We add a vray displacement node on every object to control the subdiv (like 1 for a wall, 2 or 4 for a more complex geometry etc...) but without increasing the value over 4.
The edge length is set at 4 for everything.
Is it a bad way to do ?

I've seen in vrscenes that a subdivided mesh go through a GeomStaticSmoothMesh.
And the meshes with displacement control have more parameters in the vray plugin (view_dep, edge_length etc...).
Is there really a difference ? Even if I leave the values at default ?

As we have about 32Gb RAM in every computers of our render farm, I have set the dynamic memory limit to 20000.
But I've done some test with only 15000 or 10000 without success.

I'll try to set it to 0.

I know it's hard to judge without the scene, I'll try to pack everything...

[Svetlozar Draganov]

I've sent an email to support with images and render settings.
The scene is too complex to be sent...

Now a lot of my renders hungs at 20 or 30% with the RAM full but no processor activity at all ...

Would you please let us know the ticket number since we are not able to find your email.
Thank you very much in advance.

[CGMas]

The ticket number is #601140.
I sent it from my professional email address whereas my forum account is related to my personal email address ^^ sorry