Hybrid Back/Forward path tracing (aka BiDir without MIS)

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CodeHD
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by CodeHD »

I just started looking at this promising new feature :)

I couldn't yet find it in the current daily builds for Blender. Shouldn't it be in the luxcoreconfigs under the path depth settings or did I miss something?
(I got it working with the standalone via config file)
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by B.Y.O.B. »

CodeHD wrote: Thu Jun 27, 2019 2:57 pm I couldn't yet find it in the current daily builds for Blender.
Did you download/checkout the 2_79_maintenance branch? You need that one.
https://github.com/LuxCoreRender/BlendL ... aintenance
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by CodeHD »

ah right, that'll be it. Thanks!
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by CodeHD »

Ok from how I understood this thread the following behaviour is at least intended with the current hybrid implementation, just want to double-check if its true?

Setup: A laser shining onto a mirror, in homogeneous volume (+ a spot light for illustrating where the mirror is). The path after the mirror is well rendered, but not before the mirror (i.e. standard path behaviour there):
hybrid_purelaser.png
When I put a glass plate in the laser beam, the beam appears behind it.
hybrid_glasslaser.png
Also, for some reason, if I use an ortho-camera, the spot light as no effect.

I also so far (in this scene) don't see the bug discussed in this thread: :)
viewtopic.php?f=4&t=1146
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by provisory »

As several people have already mentioned, and also visible in the test images, volumetric lights looks much brighter with hybrid PT than with BiDir.

Isn't this the same kind of thing, that was before with glossy reflections that these are handled with path tracer and light tracer too?
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by Dade »

CodeHD wrote: Thu Jun 27, 2019 4:26 pm Ok from how I understood this thread the following behaviour is at least intended with the current hybrid implementation, just want to double-check if its true?
Yes, it is a path tracing limit explained here: viewtopic.php?f=5&t=1187&start=80#p14162
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by CodeHD »

Dade wrote: Thu Jun 27, 2019 7:31 pm Yes, it is a path tracing limit explained here: viewtopic.php?f=5&t=1187&start=80#p14162
Ah right, sorry for the repost of that question then... I only had re-read the thread up to some other comment, which I thought referred to it. :oops:

I can probably live with that glass-plate workaraound for some applications anyways
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by CodeHD »

Yup, defninitely fewer errors than before with BiDir, doing well again also on a larger lens system :D
hybrid_lenssystem.png
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by B.Y.O.B. »

Neat, is that with the arbitrary clipping plane?
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Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by CodeHD »

No that is explicitely modeled like that (hence the colors in the lens cross sections indicating different glass types). I never tried doing this with clipping planes, not yet at least.
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