LuxCore: issues, problems, regressions

Discussion related to the implementation of new features & algorithms to the Core Engine.

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Re: LuxCore: issues, problems, regressions

Postby Dade » Sat Dec 16, 2017 8:32 am

stark wrote:I have troubles migrating from Lux API 1.0 to LuxCore. In particular Glossy shader differs significantly in Lux API 1.0 and LuxCore. I attached an example of this. While in Lux API 1.0 we have Glossy reflecting more light closer to tangent (like Fresnel reflection suggest) but in Lux Core tangent reflection very weak and I can't make it strong by any shader options. Is it right behavior of Glossy shader in LuxCore? Looks like not.


Can you post also the test scene ?
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Re: LuxCore: issues, problems, regressions

Postby stark » Sat Dec 16, 2017 9:07 am

Dade wrote:Can you post also the test scene ?

Yes, of course. Here the .blend file. Configured for LuxCore right now.
To render it in Lux 1.0 you need to: 1. switch to Lux 1.0 API and 2. set camera ISO from 48 to 150 (no, 120 actually, 2.5 times more not 3).

Somehow in Lux API 1.0 there is Color Space parameter Gamma in camera settings set to 2.2. But actually it works more like exposure. LuxCore have no such parameter and obviously equivalent to rendering in Lux API 1.0 with gamma = 1.0. But I'm feel not confident enough to meddle with color space settings so I leave these settings alone. There is only Scene parameter Gamma in Lux Core but it not works that way. So I adjust ISO instead to get comparable result.
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glossy-shader-compare.blend
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Last edited by stark on Sat Dec 16, 2017 10:26 am, edited 2 times in total.
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Re: LuxCore: issues, problems, regressions

Postby burnin » Sat Dec 16, 2017 9:23 am

Would you kindly post a scene? Much depends on the settings used. / disregard, had missed couple of posts :D

Here i got same shading, the only difference is in tone mapping - LuxCore has slightly brighter exposure (yet i used the same Linear / Camera values)
Lux_API-comparison.jpg

GlossyShaderCompare.7z
(928.2 KiB) Downloaded 11 times

HDR used:HDR Hangar (GrabCAD)
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Re: LuxCore: issues, problems, regressions

Postby stark » Sat Dec 16, 2017 10:17 am

burnin, probably I need to specify that I compare LuxCore API and his Path with Lux 1.0 and his legacy Path (and not Lux API 1.0 together with LuxCore Path OpenCL). I'm unable to render Glossy in Lux API 1.0 with any LuxCore algorithm because of
Code: Select all
[2017-12-16 21:26:51 Warning: 12] LuxCoreRenderer supports only Matte, Mirror, Glass, Glass2, Metal, MatteTranslucent, Null, Mix, Glossy2, Metal2, RoughGlass, Velvet and Cloth material (i.e. not N3lux14GlossyCombinedE). Replacing an unsupported material with matte.

and I have no other Glossy shader available in shaders list.

I'm not registered at GrabCad, so sorry but I'm unable to rerun your test. So i tested your scene with available HDR.
That vertical 1 px shift also not because of my poor graphics editing skills but inherent to renders. But this is minor oddity, more to explain bright contour in the difference image.
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lux-glossy-compare-2.jpeg
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Re: LuxCore: issues, problems, regressions

Postby burnin » Sat Dec 16, 2017 12:08 pm

Oh, forgot to specify... I'm using LuxCore SDK binary build on win7.
Resulting test with Classic API: Path VS LuxCore Path :|
002-ClassicDifference_Path-VS-LCPath.jpg
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Re: LuxCore: issues, problems, regressions

Postby stark » Sat Dec 16, 2017 12:39 pm

Thank you, burnin. I'll try to take recent binaries from SDK or some other more recent build to circumvent "glossy not available in Lux 1.0 with LuxCore algorithms" issue. I'm under Linux so I have no access to daily builds.
But I'm clearly see the same tendencies I'm talking about on your render: the more off-center of the ball - the more difference in specular light intensity is seen.
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Re: LuxCore: issues, problems, regressions

Postby B.Y.O.B. » Sat Dec 16, 2017 2:04 pm

Here's a fresh linux build (statically linked, 64 bit, No-OpenCL): https://www.dropbox.com/s/p5x1tkn2krvyg ... e.zip?dl=1
Hope it works for you.
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Re: LuxCore: issues, problems, regressions

Postby Dade » Sat Dec 16, 2017 2:56 pm

I have the feeling Stark is using the old LuxBlend API v1.x mode and goes trough the classic GUI and the LuxCoreRenderer "emulator". While Burnin is simply using the LuxBlend API v2.x mode and directly LuxCore API.

Stark, the old stuff is not maintained anymore and it will be dropped very soon. Can you try to use directly the LuxBlend API v2.x mode as Burnin does ?
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Re: LuxCore: issues, problems, regressions

Postby stark » Sat Dec 16, 2017 3:31 pm

Hi B.Y.O.B.! Hi Dade! It seems like despite all my efforts I was greatly misunderstood.

My main complain is about native LuxCore API with its native LuxCore Path/Path OpenCL. I eagerly dropped Lux API 1.0 (Lux Classic) about 2 years ago in favor of brand new LuxCore - it is more handy and able to render on GPU. Thank you for fresh build. It is your deserved weekend after all. It is mostly unusable for me cause I need OpenCL badly. But I can test LuxCore Path with it.

Now what I have:
1. 2.5x difference in ISO between LuxCore Path and Lux API 1.0 Legacy Path is gone and here is only slight difference in brightness as burnin mentioned.
2. I still cannot render via Lux API 1.0 with LuxCore algorithms (but I'm don't care, I'm not need this) - it was just mentioned in conversation with burnin because that stopped me from repeating his test.
3. I still have great difference in glossy shader between Lux API 1.0 + Legacy Path and LuxCore API + LuxCore Path/Path OpenCL as illustrated in that image:
Image.
View full image: http://www.luxrender.net/forum/download/file.php?id=26169&mode=view.
Also I uploaded file by Dade's request: http://www.luxrender.net/forum/download/file.php?id=26170 .

What I'm expecting? It seems weird to me that in new LuxCore specular intensity of the Glossy Shader drops as angle becomes more shallow, while intuitively, with Fresnel in mind, it should be other way around. In Lux API 1.0 with Legacy Bidir/Path Glossy Shader behaves intuitively.

So I'm merely asking:"Does you able to reproduce it?". If it is, than "Is it normal?" If it again is, than "Why so"? As I pointed earlier it is counterintuitive with Fresnel in mind.

Now I'm trying to repeat with LuxCore API + LuxCore Path OpenCL thing that looked great in Lux API 1.0 + Legacy Path and result is... less than good. I'm already about 30 hours on it and have a lot of frustration because of it :cry: Research finally pointed me to 'faulty' Glossy Shader in LuxCore. So I went there with my question about is that thing, that I observe, is right thing or some bug.

My English isn't great I know, but I hope it is not outright gibberish.

Thank you.
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Re: LuxCore: issues, problems, regressions

Postby Dade » Sat Dec 16, 2017 4:05 pm

This is the problem:

stark wrote:3. I still have great difference in glossy shader between Lux API 1.0 + Legacy Path and LuxCore API + LuxCore Path/Path OpenCL as illustrated in that image:


and this is the test case:

stark wrote:Also I uploaded file by Dade's request: http://www.luxrender.net/forum/download/file.php?id=26170 .


Ok, going to check what is going on.

P.S. I was a bit mislead by the mention of this problem:

stark wrote:2. I still cannot render via Lux API 1.0 with LuxCore algorithms (but I'm don't care, I'm not need this) - it was just mentioned in conversation with burnin because that stopped me from repeating his test.
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