Darker Interior renders faster than Lighter Interior scene. How can I optimize interior renders?

[Daniel_Ray]

I was using this old scene for a project to test interior renders. In Octane I would render brighter then darken in post. Octane had problems resolving noise in the darks(not the only problem with Octane) which ultimately led me to switching to Vray.

Now in Vray the opposite happens. I am rendering faster with darker interiors rather than lighter. I'm guessing this has to do with the adaptive lights which is cool. What could I do to speed up the brighter interior scene with multiple lights and no sunlight?

My light source is just a modo material that has the luminous intensity at 39 for the brighter scene. I'm also using brute force for the main GI engine and Light Cache at 1500 subdivs. I reduced the render time by deleting all the render elements to 7 minutes.

I have a feeling I messed something up. Any help appreciated. Thanks.

[boyan]

Hey, Daniel.

Well, I will tell you what I will do in this case. To speed up render decrease the Min. Shading rate to 5. If you don't have the glass windows disable the GI, most of the light in your scene is coming from the polygons. Replace the polygon light with area light or make them mesh light as well. Try changing BF/LC with IM/LC. Decrease the Max.Subdiv to 50 or lower and use denoiser option as well.

Cheers,

[vladimir.nedev]

My light source is just a modo material that has the luminous intensity at 39 for the brighter scene.

Replace it with actual area lights.
A luminous material contributes only as GI, and if it has a relatively small area, the result will be very noisy.
By replacing it with an area light, you will allow V-Ray to sample it more efficiently and it will also be optimized with the adaptive lights.

Reset all other render settings to defaults and only change Image Sampler to Adaptive and the Max Subdivs and Threshold if you need to.

Greetings,
Vladimir Nedev

[Daniel_Ray]

Hey, Daniel.

Well, I will tell you what I will do in this case. To speed up render decrease the Min. Shading rate to 5. If you don't have the glass windows disable the GI, most of the light in your scene is coming from the polygons. Replace the polygon light with area light or make them mesh light as well. Try changing BF/LC with IM/LC. Decrease the Max.Subdiv to 50 or lower and use denoiser option as well.

Cheers,

Hey, I tried using Irradiance Map but the result did not look anything like the Brute Force Render.

I tried using denoiser again after you suggested. Results look very good , although I seem to be losing a lot of detail in the glass reflections unless I lower the radius and have very low strength. Does that mean I need to lower my noise threshold in the image sampler? It's at .01. I think denoiser is the right direction to go, I'm just not sure how it works just yet.

Thanks for the help.

[boyan]

Hey,

Does that mean I need to lower my noise threshold in the image sampler?

If you want the clean result, yes it is. If you have reflection noisy don't reduce the Min.Shading rate. You can try to reduce the threshold but bare in mind this can increase the render time.

I tried using denoiser again after you suggested. Results look very good , although I seem to be losing a lot of detail in the glass reflections

Well, as some user do - they added back the details in post-production as using one of the denoised render elements and blend it with denoised result basically, they've been added a some noisy. This allows more control and it is a cheap and fast method.

Also, if you reduce threshold, denoiser will be more accurate.

Cheers,

[Daniel_Ray]

Replace it with actual area lights.
A luminous material contributes only as GI, and if it has a relatively small area, the result will be very noisy.
By replacing it with an area light, you will allow V-Ray to sample it more efficiently and it will also be optimized with the adaptive lights.

Reset all other render settings to defaults and only change Image Sampler to Adaptive and the Max Subdivs and Threshold if you need to.

Greetings,
Vladimir Nedev

Okay I will look into vray area lights tommorow as well as the new stuff Boyan suggested.

Thanks to you both.

[Daniel_Ray]

Replace it with actual area lights.
A luminous material contributes only as GI, and if it has a relatively small area, the result will be very noisy.
By replacing it with an area light, you will allow V-Ray to sample it more efficiently and it will also be optimized with the adaptive lights.

Reset all other render settings to defaults and only change Image Sampler to Adaptive and the Max Subdivs and Threshold if you need to.

Greetings,
Vladimir Nedev

Vray Light Material was faster. But I don't know why but when I tried using area light with a light mesh it got slower. There is vray fog in the scene and I had to readjust the fog because of the light mesh. I have to re-test because I may have changed the frame size and such.

[Daniel_Ray]

Vray Light Material renders a region at 3m 31s while Modo material renders at 5m58 seconds. I think the issue with the area light was me making it too bright and slowing down the render(I had my radiance high on the area light).

Do you guys think there would be even more improvement if I use vray light mesh instead of light material?

Thanks again.

[vladimir.nedev]

Vray Light Material renders a region at 3m 31s while Modo material renders at 5m58 seconds. I think the issue with the area light was me making it too bright and slowing down the render(I had my radiance high on the area light).
Do you guys think there would be even more improvement if I use vray light mesh instead of light material?
Thanks again.

That's strange, there shouldn't be a big difference between V-Ray Light Material and MODO material with luminance.

It's fastest if you use a rectangular light, not a mesh light.
Although, with this many lights, I am not sure.
At some point, if a large enough part of the surfaces in the scene are self-illuminated, the light material might actually be faster than individual lights, because the GI rays will hit a light surface a lot of the time.

But you do need to match the intensity, or comparing the render times is pointless.

Greetings,
Vladimir Nedev

[Daniel_Ray]

That's strange, there shouldn't be a big difference between V-Ray Light Material and MODO material with luminance.

It's fastest if you use a rectangular light, not a mesh light.
Although, with this many lights, I am not sure.
At some point, if a large enough part of the surfaces in the scene are self-illuminated, the light material might actually be faster than individual lights, because the GI rays will hit a light surface a lot of the time.

But you do need to match the intensity, or comparing the render times is pointless.

Greetings,
Vladimir Nedev

Seems like the vray environment fog is slowing down the render using a light mesh.

edit:

I am also getting an warning overbright or invalid color. My materials are still modo materials if that makes any difference at all.