[BUG?] fresnel scale in phong

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u3dreal
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[BUG?] fresnel scale in phong

Post by u3dreal » Mon Nov 27, 2006 8:40 am

Hi all , Hi nick,

here is what i found when finetuning M2I materials

I downloaded maxwell free version to have some to start with.

here is the maxwell result.

Image

and here the indigo result. with same color for diffuse and specular. and some thweaking for weight ( now available in M2I ) plus reverse gamma correction

Image

The result is pretty satisfying i think. :D

But there is one thing i noticed. The highlight at glazing angles is brighter
than the other one and difference is bigger than in the maxwell pic.
If i turn specular color to [0,0,0] then i still get some reflection
at glazing angles.and the hightlight :roll:
Is this correct ?

Image

When setting fresnelscale to 1.0 the reflections get even brighter..

So it seems the fresnel scale only adds more reflection to the specular lobe. is this correct ?? :roll:

Doesn't the fresnel scale weight the diffuse/specular depending on viewingangle ?? Just like ior does in other renderrers like maxwell ??
I'm pretty confused :roll:

Or is this a bug after all ?

cheers

u3dreal ;)
Image
3DSMax/Blender -> Indigo website:http://r3ndr.com
My Indigo Gallery !

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u3dreal
Posts: 346
Joined: Sun Jul 02, 2006 10:36 am

Post by u3dreal » Tue Nov 28, 2006 1:09 am

Ok here with the new equation .. :D

without RGC on specular color.. fresnel scale 1.0

Image

The result is very good i think only the reflection is a bit too much especially at 90°...maybe i need to apply RGC to specular color as well..

and here with RGC on specular .. fresnel scale 1.0

Image

Ok now it's really good .. only the reflection at 90° seems to be too bright..it seems indigo assumes [1.0,1.0,1.0] for reflection color at 90°

Ok so my wish would be indigo gets the color for reflection at 90°
form the <specular> element then everything should be just fine..

cheers

u3dreal ;)
Image
3DSMax/Blender -> Indigo website:http://r3ndr.com
My Indigo Gallery !

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CTZn
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Location: Paris, France

Post by CTZn » Fri Dec 01, 2006 5:27 pm

Hello u3dreal,

Well, I think it is safe to assume that it is good to have specular and fresnel effects separated, they are not linearly related in every case I believe.
So it seems the fresnel scale only adds more reflection to the specular lobe. is this correct ??
Yes, if the viewing angle is not 0° :)

My reason for posting was: what are you calling RGC ? I can't find this within the whole forums :?

thx

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zsouthboy
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Post by zsouthboy » Fri Dec 01, 2006 6:06 pm

Reverse gamma correction.

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u3dreal
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Post by u3dreal » Sat Dec 02, 2006 4:52 am

YES !!!

cheers

u3dreal ;)

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CTZn
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Location: Paris, France

Post by CTZn » Sat Dec 02, 2006 9:00 am

Ok, thank you !

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