Alain <aze### [at] qwertyorg> wrote:


> >> Alain<aze### [at] qwertyorg> wrote:
> >>
> >>> phong and specular highlighting can coexist in any single finish.
> >>> Usefull for highlight that have a sharp, bright, center area surrounded
> >>> by a relatively dim broad and fuzzy area.
> >>>
> >>> The toon part should use low brilliance, possibly as low as zero. That
> >>> make the illumination angle independant, resulting in flat textures
> >>> typical to most toons.
> >>>
> >>> For most models of diffuse, you shouls take a look at the brilliance. It
> >>> controlls the relation between the incident light angle relative to the
> >>> normal of the surface.
> >>>
> >>> In POV-Ray, fresnel is a reflection component. It needs an ior to work
> >>> (in interior), but not any transparency. If the fresnel from blender
> >>> affect the coloration of the highlights or reflection, then you should
> >>> use the metallic keyword.
> >>>
> >>> Also, take a look at the exponent and falloff for the reflection.
> >>>
> >>> Version 3.7 beta dependent:
> >>> aoi pattern: depends on the direction from whitch the surface is
> >>> observed. Takes vewing from reflection and refraction into acount.
> >>>
> >>>
> >>> Alain
> >>
> >> Thanks, all this will be very helpfull.
> >>
> >> Blender diffuse fresnel shader is not the ior dependant raytraced
> >> reflections,
> >> those can be set up separately too. instead, it's using an indice to
> >> vary the
> >> diffuse shading, normal dependant with it's reference ray based on the
> >> lamp, not
> >> on the view. Blinn on the other side is a "non raytraced specularity that
> >> correctly computes its intensity and extension via Snell's Law." using
> >> user
> >> input ior.
> >>
> >> 1-To emulate that in Pov, would an extreme exponent with raytraced
> >> reflection
> >> improve rendertimes to be comparable with a non raytraced specular?
> > I don't think so.
> > Blinn seems to emulate or fake fresnel based variable reflection.
> >>
> >> 2-What's the difference between aoi and slope_map?
> >>
> >
> > Those two are similar in implementation but differs as follow:
> >
> > slope depends on the orientation of a surface relative to an arbitrary,
> > user defined, direction. If you move the camera, the resulting pattern
> > will never change. If you view the same object directly and it's
> > reflection, there is no change to the pattern.
> > Typicaly, the values can range from 0 to 1. There is an optional
> > altitude component that allow the texture to change acording to the
> > "altitude" as well as it's local slope.
> > In your case, it could be the lamp-object vector.
> > If you need it to take more than one light_source, you'll need to layer
> > several pattern using partialy transparent pigments, one per light_source.
> >
> > aoi depends on the orientation of a surface relative to the direction at
> > whitch it is observed. If you move the camera, the resulting pattern
> > will always change acording to the new location. Typical values range
> > from 0 to 0.5. The 0.5 to 1 range belong to the part that's facing away
> > from the point of view and normaly not visible unless the normal gets
> > disturbed.
> > aoi is not available in version 3.6 and earlier. There is a version of
> > that pattern implemented in megapov, but it don't function the same way.
> > ____________________________________________________________________
> >  >>>> Toon |brilliance probably below 1
> > Change that to: brilliance under 0.25, probably closer to 0
> >
> > Make some tests using a box and a plain sphere using a bland white pigment.
> >
> >
> >
> > Alain
> Also, for the toon part:
> You may also look for a finish with a low diffuse value and a high
> ambient value.

Yes I had noticed about the low diffuse value. about the high ambient, I have
doubts since toon shaders still need to be able to get good dark shadows.

Thanks a lot for your help.

For the Blinn, after some tests I chose to use just the specular keyword, So I
had to leave the blender IOR feature out.
For phong an Cooktorrence, the same phong and phong_size.
For wardiso I used the specular keyword with an increased specularity when spec
area is set tighter.




About Oren Nayar:
The values below 1 for brilliance give terminator problems (blocky limit between
light and shadow) even if I forget about that, varying the brilliance doesn't
seem enough to look as good as the oren nayar. which seems to process by
lightening the edge when increasing its contrast sigma whereas brilliance rather
seems to darken by extending the shadows towards parts more influenced by light.
I still left things that way to be able to move on.

Other than that I Only have Fresnel and Minnaert left to do, but they're a pain
to conciliate with the texture system I had set up, which already had to make
use of the "russian mafia doll "finish map"" to map specular to a texture along
with alpha to a different texture along with diffuse image map and bump map.
I gave up all the other blender channels, to keep a little sanity, which I'm
preparing to waste in my fresnel / minnaert attempt :-)

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