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Cauchy B Coeff might produce wrong results?
Posted: Sun Nov 15, 2015 1:45 am
by Silverwing
Hi there,
I just rendered my glass scene again over night (17h) with a little dispersion.
However the Result is not giving me what I have expected.
Render algorithm was MLT-BiDir but it looks the same in Pathtracing-BiDir.
The Renderer was
Indigo fo Cinema 4D 3.8.26.2
Cauchy B Coeff was 0.005
Here is the original render. Same Material but without the Cauchy B Coeff
It looks more natural (is not brighter then the background).
Also notice the silhouette of the glass thickens inside the glass is much more pronounced with the Cauchy B material.
Cheers,
Raphael
Re: Cauchy B Coeff might broduce wrong results?
Posted: Sun Nov 15, 2015 4:34 am
by zeitmeister
This is strange and definately shouldn't look that way. Did you check your scene scale?
Cheers, zeiti
Re: Cauchy B Coeff might broduce wrong results?
Posted: Sun Nov 15, 2015 5:48 am
by contegufo
Hi
The scene was lit by an environment map?
Re: Cauchy B Coeff might broduce wrong results?
Posted: Sun Nov 15, 2015 7:49 am
by Silverwing
zeitmeister wrote:This is strange and definately shouldn't look that way. Did you check your scene scale?
Cheers, zeiti
The Scene scale should match real world. I´m not sure if it fits exactly because I do not know exactly what scale is exported by cindigo. But at least in C4D everything is in scale.
zeitmeister wrote:This is strange and definately shouldn't look that way. Did you check your scene scale?
Cheers, zeiti
Yes the scene is lit entirely by a HDRI 360° map.
I should mention that this is the result of a linear output. (Untonemapped EXR)
It looks perfect with Cauchy B set to 0.
Cheers,
Raphael
Re: Cauchy B Coeff might broduce wrong results?
Posted: Sun Nov 15, 2015 11:55 pm
by thesquirell
Dear Raphael,
Cindigo will export in scale which is chosen in Render Setting, Enviroment, Scene scale. I think it just takes the numbers from the scene and it just takes them as they are, without conversion. But I am not sure about that. To avoid all the confusion about the scale etc. I make sure my project settings say the same scene scale as Scene scale in cindigo's render setting, which is the same as unit display in C4D's preferences. Play safe!
Would love to hear how this develops. Never had any problem with CBC before.
Re: Cauchy B Coeff might broduce wrong results?
Posted: Mon Nov 16, 2015 12:48 am
by zeitmeister
What Happens if you use the cindigo version before? And does it come correctly of you use a coefficient of 0.001?
Cheers, zeiti
Re: Cauchy B Coeff might broduce wrong results?
Posted: Mon Nov 16, 2015 2:10 am
by Oscar J
Oh my. Though Indigo at least had its basics right.
Re: Cauchy B Coeff might broduce wrong results?
Posted: Mon Nov 16, 2015 2:21 am
by OnoSendai
Hi, send over the scene, I'll take a look (eventually).
Re: Cauchy B Coeff might produce wrong results?
Posted: Mon Nov 16, 2015 4:56 am
by Silverwing
thesquirell wrote:Dear Raphael,
Cindigo will export in scale which is chosen in Render Setting, Enviroment, Scene scale. I think it just takes the numbers from the scene and it just takes them as they are, without conversion. But I am not sure about that. To avoid all the confusion about the scale etc. I make sure my project settings say the same scene scale as Scene scale in cindigo's render setting, which is the same as unit display in C4D's preferences. Play safe!
Would love to hear how this develops. Never had any problem with CBC before.
Yes that´s what I have been doing too. I checked the scene scale with the apperture. Whrong translations end up with the wrong DOF. So if the DOF is way to strong or not there with a Apperture 3.5 you know there is something off the scale.
I have set the Scale to mm within C4D and within the Exporter.
I changed it to cm and to m just to see if it makes a difference. But unfortunately it does not. Cauchy B always has that magenta tint.
zeitmeister wrote:What Happens if you use the cindigo version before? And does it come correctly of you use a coefficient of 0.001?
Cheers, zeiti
No I have not checked yet. Maybe I should.
I have instead exported it to the latest Indigo standalone v3.8.29
I added some pictures:
- Picture with Cauchy B at 0
- Picture with Cauchy B at 0.00001
I will upload the scene later.
Cheers,
Raphael
Re: Cauchy B Coeff might produce wrong results?
Posted: Wed Nov 18, 2015 12:40 am
by Silverwing
As Promised here´s the scene.
I hope this *.pigs file works!
If not just write me a line!
GLASS-SCENE
Cheers,
Raphael
Re: Cauchy B Coeff might produce wrong results?
Posted: Wed Nov 18, 2015 1:39 am
by OnoSendai
Thank Sliverwing.
Looks like it's a problem with the combination of dispersion (single wavelength rendering), and non-post-process aperture diffraction.
Easy workaround - use post-process aperture diffraction only (or turn it off).
Re: Cauchy B Coeff might produce wrong results?
Posted: Thu Nov 19, 2015 12:28 am
by Silverwing
OnoSendai wrote:Thank Sliverwing.
Looks like it's a problem with the combination of dispersion (single wavelength rendering), and non-post-process aperture diffraction.
Easy workaround - use post-process aperture diffraction only (or turn it off).
Oh such an easy fix. Thanks a lot for having a look at the scene!
Much appreciated!
Cheers,
Raphael
Re: Cauchy B Coeff might produce wrong results?
Posted: Fri Nov 20, 2015 1:07 am
by Silverwing
Sorry for being so picky.
Yes the Aperture Fix got rid of the coloring. But I still get this stange "Artifact" in the rendering with Chauchy B Coeff. The Silhouette of the glass gets much more pronounced (Marked Green). I think there is something off!
P.s. I used the old colored rendering for comparison. The test with the Aperture fix only gets rid of the color!
Cheers,
Raphael
Re: Cauchy B Coeff might produce wrong results?
Posted: Fri Nov 20, 2015 1:37 am
by OnoSendai
That's no problem for being picky, good spotting
There's a known issue/limitation with the dispersion code that I should probably fix. It's to do with the computation of the fresnel reflection term and the actual (waveelength-dependent) IOR for the wavelength as opposed to the base wavelength.
Re: Cauchy B Coeff might produce wrong results?
Posted: Fri Nov 20, 2015 6:29 am
by galinette
What if you increase cauchy B to a value such as 0.005?