Noob questions about luxcore

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crazerep
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Re: Noob questions about luxcore

Post by crazerep » Wed Oct 23, 2019 11:38 am

Yeah its fine thanks, i added a spotlight instead of point light. looks good to me :D
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light scatter.blend
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Martini
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Re: Noob questions about luxcore

Post by Martini » Wed Oct 23, 2019 1:02 pm

Looks great to me too. Well done!
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crazerep
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Re: Noob questions about luxcore

Post by crazerep » Thu Oct 24, 2019 3:48 am

thanks to you (:

Although Now i need to know if i can exclude lights from interacting with objects.

Ill share you the file. Now im thinking why even should i have a box with volume parameters on when world volume gives what i want :!

This is a scene where i want the red scattered light to be prominent- while i have other lights helping to light a model infront of it.

So if i increase the scattering scale- this would multiply the whole scene with other lights. as there will be more light.

What i think would work is if theres a way to render in a layer of one scene with red scattered light only.

and the other scene lighting up the elements.

or is there any other work around like excluding lights on specific elements?

Cheers
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Martini
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Re: Noob questions about luxcore

Post by Martini » Thu Oct 24, 2019 7:09 am

crazerep wrote:
Thu Oct 24, 2019 3:48 am
What i think would work is if theres a way to render in a layer of one scene with red scattered light only.

and the other scene lighting up the elements.

or is there any other work around like excluding lights on specific elements?
You can assign lights to light groups and then adjust their brightness after rendering, but I don't know of a way for LuxCore to do exactly what you're asking. Mainly because it's not "realistic" for a light source not to interact with a volume, and LuxCore generally does things in a physically correct way. Maybe someone else knows?

You could perhaps render 2 different scenes, one where volume objects and volumetric lights are disabled using Blender's collections/view layers, and then use the Blender compositor to combine the results. Again I feel I'm beyond my own knowledge here :) Sorry

Edit: Also it doesn't help that when I load your scene, viewport rendering works, but if I try to do a render Blender freezes for me. I just installed Linux so perhaps I still have some config to iron out... :? It only happens on this version of the scene though, the other one renders fine :cry:
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crazerep
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Re: Noob questions about luxcore

Post by crazerep » Thu Oct 24, 2019 9:26 am

Martini wrote:
Thu Oct 24, 2019 7:09 am

Edit: Also it doesn't help that when I load your scene, viewport rendering works, but if I try to do a render Blender freezes for me. I just installed Linux so perhaps I still have some config to iron out... :? It only happens on this version of the scene though, the other one renders fine :cry:
:o damn, then destroy that file immediately xD

I see what you mean, Thanks alot Martini!

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B.Y.O.B.
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Re: Noob questions about luxcore

Post by B.Y.O.B. » Thu Oct 24, 2019 2:00 pm

Martini wrote:
Thu Oct 24, 2019 7:09 am
Edit: Also it doesn't help that when I load your scene, viewport rendering works, but if I try to do a render Blender freezes for me.
It might be a bug in LuxCore, if you can reproduce it, can you create a bug report about it?
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Martini
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Re: Noob questions about luxcore

Post by Martini » Fri Oct 25, 2019 10:07 am

B.Y.O.B. wrote:
Thu Oct 24, 2019 2:00 pm
Martini wrote:
Thu Oct 24, 2019 7:09 am
Edit: Also it doesn't help that when I load your scene, viewport rendering works, but if I try to do a render Blender freezes for me.
It might be a bug in LuxCore, if you can reproduce it, can you create a bug report about it?
It seems to be related to Direct Light Sampling Cache (DLSC). If I turn that off, the render starts immediately. If I turn it on, I can see output in the console from Lux about SceneVisibility trace thread count: 16, then it freezes and I have to kill the blender process.

Code: Select all

[LuxCore][48.329] Configuring 16 CPU render threads
[LuxRays][48.330] Preprocessing DataSet
[LuxRays][48.330] Total vertex count: 3473
[LuxRays][48.330] Total triangle count: 1932
[LuxRays][48.330] Preprocessing DataSet done
[LuxRays][48.330] Adding DataSet accelerator: EMBREE
[LuxRays][48.330] Total vertex count: 3473
[LuxRays][48.330] Total triangle count: 1932
[LuxRays][48.335] EmbreeAccel build time: 5ms
[LuxCore][48.335] Building DirectLightSamplingCache
[LuxCore][48.335] DirectLightSamplingCache evaluating best radius
[LuxCore][48.451] DirectLightSamplingCache best radius: 108.451
[LuxCore][48.451] SceneVisibility trace thread count: 16
After this time, Blender is entirely unresponsive and I can see one CPU core after another hit 100%, then it will drop to 0 and pick a different core to 100%, then another, and just keep cycling. The time that each core stays at 100% starts to slowly increase. I was only able to observe this for a few minutes before my CPU became busy with another task. I am using Ubuntu Linux if that makes a difference.

Right after starting the render:
Screenshot from 2019-10-25 21-09-00.png
Right after starting render
After going for about a minute you can see the time spent on each core increasing
Screenshot from 2019-10-25 21-09-49.png
You can see the cycle time increasing
You can also see in the background that Blender has not even had a chance to update the render window contents after it opened. It still has the ghost of what was behind it :lol:

I am not sure exactly how DLSC is supposed to work, and whether it has problems when there are only 2 light sources and a Homogeneous World scattering volume. So I hesitate to call it a bug, perhaps it just is normal to have a really long compute time? I never used it. Let me know if you know.

Edit: added screenshots
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Dade
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Re: Noob questions about luxcore

Post by Dade » Fri Oct 25, 2019 10:32 am

What is the size of your scene ? In what unit are working ?

Code: Select all

[LuxCore][48.451] DirectLightSamplingCache best radius: 108.451
108.451 is a sky high value, have you changed some default value ?
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Martini
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Re: Noob questions about luxcore

Post by Martini » Fri Oct 25, 2019 12:19 pm

Dade wrote:
Fri Oct 25, 2019 10:32 am
What is the size of your scene ? In what unit are working ?

Code: Select all

[LuxCore][48.451] DirectLightSamplingCache best radius: 108.451
108.451 is a sky high value, have you changed some default value ?
I don't know, sorry. I am rendering the scene that crazerep posted above ^^^

There is only a ground plane and 2 objects plus 2 lights ..
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