Transitioning from VRay to LuxCoreRender

Discussion related to the Engine functionality, implementations and API.
happyboy
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Re: Transitioning from VRay to LuxCoreRender

Post by happyboy » Mon Jul 01, 2019 12:05 pm

Thanks, B.Y.O.B and Dade.
Dade wrote:
Sun Jun 30, 2019 9:00 am
Note: PhotonGI doesn't support radiance groups at the moment.
ah... Is supporting radiance groups in PhotonGI officially planed? How difficult is it? No good way to do it? Or it can be done, but there may be some penalty/restrictions? Or nothing really difficult, but needs time to implement/test?

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Dade
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Re: Transitioning from VRay to LuxCoreRender

Post by Dade » Mon Jul 01, 2019 12:49 pm

happyboy wrote:
Mon Jul 01, 2019 12:05 pm
Thanks, B.Y.O.B and Dade.
Dade wrote:
Sun Jun 30, 2019 9:00 am
Note: PhotonGI doesn't support radiance groups at the moment.
ah... Is supporting radiance groups in PhotonGI officially planed? How difficult is it? No good way to do it? Or it can be done, but there may be some penalty/restrictions? Or nothing really difficult, but needs time to implement/test?
It more a matter of memory usage: you need a separate cache for each light group (it is a bit expansive). I also wonder if it is worth doing because rendering time with the cache are really low. Light groups were development many years ago when rendering time was measured more in days than minutes.
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Luxart
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Re: Transitioning from VRay to LuxCoreRender

Post by Luxart » Tue Jul 02, 2019 5:45 am

Shall we remove Light groups and Tile Path, Both are rarely used and of little use.

happyboy
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Re: Transitioning from VRay to LuxCoreRender

Post by happyboy » Tue Jul 02, 2019 6:14 am

Dade wrote:
Mon Jul 01, 2019 12:49 pm
It more a matter of memory usage: you need a separate cache for each light group (it is a bit expansive). I also wonder if it is worth doing because rendering time with the cache are really low. Light groups were development many years ago when rendering time was measured more in days than minutes.
I see. Our use case is a bit special: we're actually evaluating luxcore as a render backend for our in-house software, whose users are usually NOT professional designers. They want to get good renders fast (that's why I'm currently not considering Appleseed because it appears to be quite slow when compared with luxcore with DLSC+PhontonGI). Also, adjusting radiance group SCALES in a compositor program (we can develop one as a part of our software) is much more intuitive for them, so I think combining PhotonGI's speed with radiance group's flexibility is very helpful for us.

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B.Y.O.B.
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Re: Transitioning from VRay to LuxCoreRender

Post by B.Y.O.B. » Wed Jul 03, 2019 9:02 am

I have split some posts into a new thread: viewtopic.php?f=10&t=1197#p14282
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happyboy
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Re: Transitioning from VRay to LuxCoreRender

Post by happyboy » Thu Jul 04, 2019 5:15 am

B.Y.O.B. wrote:
Wed Jul 03, 2019 9:02 am
I have split some posts into a new thread: viewtopic.php?f=10&t=1197#p14282
Thanks! Now a slight off-topic question (not directly related to VRay): since PhontoGI doesn't support radiance groups, can I do two renders without loading the scene twice? Like this:
- load scene
- render first radiance group (by removing all other lights)
- render second radiance group (by removing other lights and re-add lights in second radiance group)

This way, at least I can avoid reloading the scene twice, which is faster than two complete renders.

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Re: Transitioning from VRay to LuxCoreRender

Post by happyboy » Thu Jul 04, 2019 2:01 pm

One more question: According to the "Advances features" pages, "Using light groups, one can interactively adjust the color temperature of any light source during rendering without losing the rendered samples." Is this still supported when NOT using photonGI? I've skimmed over the codes related to "scene editing" but can't find any code updating rendered samples. Maybe they're done in a clever way that I didn't notice.

But I was trying to do similar things via post-processing. I thought lighting is linear, so if there is only one light, e.g. a rectangular area light, whose gain=50. Then if I change it to gain=100 and no tonemapping, every pixel's luminance should be doubled. Simple experiments proved me wrong, but it looks like for every pixel I examined, doubling the gain approximately makes the luminance *1.37 (I tried to increase gain from 12.5->25->50->100, each doubling yield apprixmately luminance*1.37 for every pixel I examined).

Anyway, is there a simple way to update the whole image by multiplying every light's gain by the same number? I haven't used corona but I've heard its "LightMix" feature is doing something similar (adjust lighting via in a postprocessing program)

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Re: Transitioning from VRay to LuxCoreRender

Post by B.Y.O.B. » Thu Jul 04, 2019 2:07 pm

since PhontoGI doesn't support radiance groups, can I do two renders without loading the scene twice? Like this:
- load scene
- render first radiance group (by removing all other lights)
- render second radiance group (by removing other lights and re-add lights in second radiance group)

This way, at least I can avoid reloading the scene twice, which is faster than two complete renders.
Yes, I think this is possible, the PhotonGI cache should automatically rebuild on EndSceneEdit().
happyboy wrote:
Thu Jul 04, 2019 2:01 pm
According to the "Advances features" pages, "Using light groups, one can interactively adjust the color temperature of any light source during rendering without losing the rendered samples." Is this still supported when NOT using photonGI?
Yes. See the "temperature" property of the light group: https://wiki.luxcorerender.org/LuxCore_ ... ance_Group
You can update imagepipeline properties by passing them to session.Parse(), like I do here:
https://github.com/LuxCoreRender/BlendL ... __.py#L298
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happyboy
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Re: Transitioning from VRay to LuxCoreRender

Post by happyboy » Fri Jul 12, 2019 2:20 am

B.Y.O.B. wrote:
Thu Jul 04, 2019 2:07 pm
Yes, I think this is possible, the PhotonGI cache should automatically rebuild on EndSceneEdit().
You're right :)
BTW: At first I was planning to use C++ SDK but later I found using pyluxcore is far easier and I'm getting latest builds automatically (on the other hand, I need to rebuild C++ SDK myself each time it has a new commit). So now I'm using pyluxcore exclusively to explore.
B.Y.O.B. wrote:
Thu Jul 04, 2019 2:07 pm
happyboy wrote:
Thu Jul 04, 2019 2:01 pm
According to the "Advances features" pages, "Using light groups, one can interactively adjust the color temperature of any light source during rendering without losing the rendered samples." Is this still supported when NOT using photonGI?
Yes. See the "temperature" property of the light group: https://wiki.luxcorerender.org/LuxCore_ ... ance_Group
You can update imagepipeline properties by passing them to session.Parse(), like I do here:
https://github.com/LuxCoreRender/BlendL ... __.py#L298
Ah.... it's imagepipeline properties instead of light properties... now I understand :)

Now a new question: what units are used in LuxCore? VRay has specific API calls to specify how long is 1 meter etc, but while Blender has unit settings, I don't see anything related in the exported cfg/scn file. At first I think it doesn't matter as long as our units are CONSISTENT but later I found "sun" which looks liky assume some specific physical units?

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Re: Transitioning from VRay to LuxCoreRender

Post by B.Y.O.B. » Fri Jul 12, 2019 7:18 am

As far as LuxCore is concerned, every length is in meters.
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