5 hours, still have noise in my render

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5 hours, still have noise in my render

Postby ghostlovescore » Tue Oct 25, 2016 11:26 am

I am working in Blender. I've been trying out Luxrender. I left it today to render for 5 hours, LuxCore Path OpenCL. I got 5000 samples per pixel and it still seems that it would need more to get rid of the noise. Compare it to Cycles and it could render very clean picture in 5 hours, but 4 times as large.

This is my render

90.png
Luxrender


And these are my settings

luxsettings.png


I am using Windows 7, Luxrender 1.6

Is there something that I could do so it could render cleaner picture? Is Luxrender even good choice for these kind of interiors with so many lights? I feel that Cycles manages it much better.
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Re: 5 hours, still have noise in my render

Postby B.Y.O.B. » Tue Oct 25, 2016 11:32 am

ghostlovescore wrote:Is Luxrender even good choice for these kind of interiors with so many lights? I feel that Cycles manages it much better.

Note that if you put an emissive material on a mesh, each triangle becomes a separate meshlight in Lux.
This can slow down rendering of such scenes quickly, I also often ran into this problem.

Sometimes it can help to play around with the light strategy (I would suggest you switch to LuxCore API mode to do that, since the Classic API controls will probably not work).
But maybe Dade or another core dev can give us better tips how to deal with scenes with many meshlights.
In Classic Lux there's the importance property/light strategy which can help to deal with this kind of scenes, but AFAIK that does not exist in LuxCore.

I also noticed that Cycles can handle many meshlights far better, their system of handling emissive materials is probably different.

edit: btw. my first tuning knob when optimizing speed in LuxCore is the path depth, it works wonders to set it to something low in the beginning (e.g. start with 2 or 3) and raise it according to the materials in the scene (glass, metal etc.).
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Re: 5 hours, still have noise in my render

Postby ghostlovescore » Tue Oct 25, 2016 11:45 am

Thanks for a quick response. Yes, that makes sense, I use Light Emission materials for these mesh lights.
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Re: 5 hours, still have noise in my render

Postby ghostlovescore » Wed Oct 26, 2016 12:26 am

And I have one more strange problem - I have three instanced mesh lights, their power is 50W. And I have the same mesh light, but not instanced, just copied. It has also 50W of power. But for some reason instanced mesh lights are a lot dimmer than non instanced mesh light that has the same geometry.
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Re: 5 hours, still have noise in my render

Postby Dade » Wed Oct 26, 2016 6:43 am

ghostlovescore wrote:And I have one more strange problem - I have three instanced mesh lights, their power is 50W. And I have the same mesh light, but not instanced, just copied. It has also 50W of power. But for some reason instanced mesh lights are a lot dimmer than non instanced mesh light that has the same geometry.


What tone mapper are you using ? Switch to "linear" before making any consideration about light strength.

BTW, LuxRender/LuxCore uses MIS between direct light sampling and surface hits to highly reduce the noise. This can be indeed a problem if you have thousands of light sources (each single emitting triangle is a light source). I assume Cycles only use surface hits to sample material emission. This can generate a lot more noise and even fireflies but it is not depended of the number of emitting triangles, it costs plain nothing compared to having to sample each single emitting triangle.

I guess it could be useful to have an option to disable MIS on emitting materials.
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Re: 5 hours, still have noise in my render

Postby B.Y.O.B. » Wed Oct 26, 2016 6:51 am

Dade wrote:I guess it could be useful to have an option to disable MIS on emitting materials.

I agree.
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Re: 5 hours, still have noise in my render

Postby ghostlovescore » Wed Oct 26, 2016 7:30 am

Dade wrote:What tone mapper are you using ? Switch to "linear" before making any consideration about light strength.


I had it on linear. I had three light meshes. When none of them are instances, the light is alright. They all glow the same. But if I make two of them as instances - same mesh, same material - those two glow dimmer than non-instanced one.
Take a look at these renders. Tonemapping settings are the same for every render. Linear, ISO800, Shutter 1/15, F4.

Non instanced
Image

Two on the left are instances
Image
They are now almost not emitting at all.

Dade wrote:I guess it could be useful to have an option to disable MIS on emitting materials.

Sounds great
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Re: 5 hours, still have noise in my render

Postby B.Y.O.B. » Wed Oct 26, 2016 7:37 am

ghostlovescore wrote:They are now almost not emitting at all.

To me it looks like they are completely off (or not exported at all).
Did you check for errors in the log?
Can you upload a simple testscene that shows the problem, maybe it's a bug in the exporter?

edit: I did a quick test with instanced area lights and instanced mesh lights, both work here.
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Re: 5 hours, still have noise in my render

Postby ghostlovescore » Wed Oct 26, 2016 7:48 am

It seems to be the problem just in my scene. New scene with 3 cubes render normal - all have the same brightness.
I have uploaded those three objects from my scene. And I don't get any error while rendering. I still get the same problem when I import them into a new scene.
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Re: 5 hours, still have noise in my render

Postby jensverwiebe » Wed Oct 26, 2016 8:24 am

The righmost "lights" are not configured the same as the rest, the have 3 materials attched. Are you aware ?
Could it be you loose/lost per face assignement from materials on importing ?

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