Slow and grainy

[cedric_vaucher]

Hello!

Can anyone give me a hint how to speed up the render time of this interior scene? It is also very grainy...

[boyan]

Hey, Cedric,

If I were in your shoes I would disable the GI and would add more lights, you can make them invisible to the camera, and I would enable the denoiser. You can adjust over exposure image to darker later in VFB or post.

Cheers

[aleksandar.kasabov]

Hello cedric_vaucher,

You can also check this article where you can find more information about the different render settings and how to use them in order to increase the quality and reduce the render times. I hope it is of help

[cedric_vaucher]

Thanks guys,
Without GI? Why not, like in the old days. I added some big area lights. It's less grainy but still relatively slow.
And where is the "Noise Threshold parameter " mentioned in the article?

[aleksandar.kasabov]

The "Noise Threshold" parameter is located in the V-Ray tab of the render settings under the Progressive Sampler rollout. Please check this screenshot.

You can also check this page for more information about the image sampler.

[sirio76]

Hello!

Can anyone give me a hint how to speed up the render time of this interior scene? It is also very grainy...

Are you using light material or self illumination?

[cedric_vaucher]

The "Noise Threshold" parameter is located in the V-Ray tab of the render settings under the Progressive Sampler rollout. Please check this screenshot.
You can also check this page for more information about the image sampler.

I was rendering with Sample Type set to bucket, without no "Noise Threshold". Is "Threshold" in Bucket mode the same?

Are you using light material or self illumination?

I've been trying a light material only solution at first (white light emitting cylinder).
Now I am trying with a light material with a Colour Multiplier of 20, so it stays white. I added a rectangle light that is as about 120x5 cm, set to invisible and and double sided. In the project tab, it is set to ignore the visible cylinder.
I will try without the Light Material.
Isn't there a kind of "mesh-light"?

[sirio76]

Unfortunately there is not light mesh yet and light material is not that optimized.
My advice is to use a simple rectangular area light for the neon, then use a cylinder with self illumination (use a vray object properties tag so that it do not cast shadows).
For the rectangular area light you can use about 1000lumens for linear meter, and a color temperature of 5500 K.
Then tune the camera exposure and be sure that is not too dark, if needed you can also add some soft box.

[cedric_vaucher]

How do you achieve self illumination – I assume with a Light Material ?

[sirio76]

You can use both a light material or activate the self illumination inside the standard material, since you need this only for the visible tube you can disable the GI option.
Try this setup, it should be plenty fast, don't forget to use the Intel denoiser (or the Nvidia if you have an Nvidia GPU).

[cedric_vaucher]

Thank you Sirio. My neon lights ended up like yours, self illuminating shader (not Light Material) and two crossed area lights.
What strikes me more is your render setting – my render time went from 20 to 2 minutes !!

This is just a test for a low key architectural visualisation. The model and the textures obviously need some work. I would add some depth of field, and so on.

I started by adding some area lights to speed up the GI. But with your render setting this isn't necessary anymore. I'll will have a closer look later.

[sirio76]

What strikes me more is your render setting – my render time went from 20 to 2 minutes !!
.

Nothing fancy, I’m just using default render settings, plus a bit of denoiser

[cedric_vaucher]

Nothing fancy, I’m just using default render settings, plus a bit of denoiser

So I compared the render settings:


Render Settings/V-Ray/

Common/Denoiser
Before: Default V-Ray Denoiser
After: Intel Open Image Denoise

V-Ray/Progressive Sampler/Noise Treshold
Before: 0.01 (default)
After: 0

Settings/Default Displacement and Subdivision/Max Subdivis
Before: 512
After: 256 (default)

Are these differences reducing this render time?
Or is it the simpler light setup?

[sirio76]

No, for test render I simply set the threshold to 0 and stop the render when is clean enough, realistically you never need to wait until you reach 0, in many scenes something between 0.01 and 0.04 will be enough and render a lot faster. The Intel and Nvidia denoiser are much more effective in removing noise (and fireflies) while preserving details.
You have no displacement in the scene, regardless I prefer to pre-tasselate the surface and use a lower max subdivision, like 20.
You get faster render because 1- area lights are far more optimized than light materials and tends to produce a lot less noise, and 2- the Intel denoiser works much better than the default one, I also change the effect update frequency that will give you faster feedback.

[cedric_vaucher]

the Intel denoiser works much better than the default one, I also change the effect update frequency that will give you faster feedback.

What denoiser should I choose with a Mac M1?