Dark edge around glossy material

Project:YafaRay
Component:YafaRay Core
Category:bug report
Priority:normal
Assigned:David Bluecame
Status:active
Description

The yafaray glossy material shows a dark edge around it that gives a feeling that it's "drawn" and slightly like a "cartoon", reducing its realism.

For example, comparing this scene in yafaray with luxrender, in yafaray. Notice the dark edge around the ball, specially in the right hand side.

Yafaray glossy - dark edgeYafaray glossy - dark edge

 

 

 

 

 

 

 

 

 

 

 

 

 

When rendering with LuxRender, it shows no dark edge, which makes it more realistic in my opinion.

luxrender glossy correctluxrender glossy correct

 

 

 

 

 

 

 

 

 

 

 

 

I'm not sure if the problem is in the code of the material or in the algorithm itself. For example, I've been digging in Internet and it seems that Luxrender had, in the past, problems with the rendering of glossy materials:

http://www.luxrender.net/forum/viewtopic.php?f=16&t=3125

They even had the hypothesis that the problem could come from the Ashikhmin and Shirley method. I don't know how they fixed that problem, or if it was really or not the algorithm.

 

Also VRay seems to suffer from this problem, for example in the next link, one of the parameters seem to be a "cheat" for the dark edges in glossy:

http://www.spot3d.com/vray/help/200R1/material_params.htm

"Fix dark glossy edges - enabling this option will fix dark edges that some times appear on objects with glossy materials"

 

In any case, I believe that fixing this issue would improve the realism of scenes with glossy materials.

Best regards. David.

Comments

#1

David, Thanks for your fantastic work on yafaray!

We really need you!

 

I agree with the issue you posted!

I haven't seen the issue on your post and I posted the same problem reporting the same issue.

http://www.yafaray.org/community/forum/viewtopic.php?f=13&t=4906

I must only add to your text that it's not just a matter of edges. It influences a plane material too.

The issue relies on the angle of the surface of the material in relarion to the camera.

If the angle between the camera and the surface is reduced the surface becames more grey and darker.

It's wrong because if this angle is smaller, the reflectance should increase. We should have a ior for glossy materials.

Therefore, the color of the edge of the sphere should be darker or brighter according to the environment.

If it's a cube the side faces should reflect more and shouldn't be just greyer.


Arquitecto can be contacted here:
Arquitectos

#2

i think yafaray ior and specular value are related (from luxrender manual)

"The IOR and specular color are related via the formula IOR = (sqrt(Ks)+1)/(1-sqrt(Ks)) (Ks is the proper term for specular color). This translates a specular color of .25 to an index of refraction of ~3. A specular color of .05 results in an IOR of approximately 1.6."

  apart frm darkedge of glossy one more issue is the diffuse value of glossy shader is reduced from the value you set,so that energy conservation (diffuse+spec = 1) is maintained.i.e. if you want white glossy(0.8,0.8,0.8), you have to set (1.0,1.0,1.0).

my old test "http://www.yafaray.org/community/forum/viewtopic.php?f=22&t=4341"

#3

Version:»
Assigned to:Anonymous» David Bluecame
Status:active» needs review

Hello,

 

I've implemented an extended Texture Mapping system. Already included in Experimental v0.1.99-beta3.

 

For links and example images see:

http://www.yafaray.org/community/forum/viewtopic.php?f=22&t=5091

 

For now it's so experimental that I have not yet created a pull request against official YafaRay.

 

I will mark this as Needs Review because perhaps we can make a more realistic glossy using Coated Glossy with the new Mirror Reflectivity Strength and the Mirror Color, Strength and IOR fresnel texture mappings. If we can make good glossy materials this way I will mark it as fixed.

 

I hope you like it!

#4

The specific issue in the original post was addressed with a fix that was included in the 0.1.5 release, so I am not sure what problem you are referring to that "needs review."

Could you possibly update this thread with new screenshots and perhaps a test blend?

#5

Hello,

I've used the last git version of Master v0.1.5 and the glossy material still does not look right in my opinion, maybe even worse? (dark edge around it). It's clearly more unrealistic than the Luxrender example.

I've attached an example blend.

 

yafaray-glossy-photonmapping-v0.1.5 git 2015-05-02yafaray-glossy-photonmapping-v0.1.5 git 2015-05-02

 

 

 

 

 

 

 

 

 

 

 

 

 

yafaray-glossy-bidirectional-v0.1.5 git 2015-05-02yafaray-glossy-bidirectional-v0.1.5 git 2015-05-02

 

 

#6

Not sure why, the blend example file did not appear in my previous reply. I hope it appears here now.

AttachmentSize
yafaray-glossy.blend 586.25 KB

#7

Status:needs review» postponed

Postponed to future YafaRay-E v3.0.0, where I will make changes to the materials system.

#8

Status:postponed» active