Am 16.08.2021 um 18:58 schrieb Chris R:

> This was my first crack at updating the scene to use fresnel reflections.  I'm
> not entirely happy with it, so I am rerunning with some different min/max
> reflection values for the pool table.  I noticed the highlights on the table
> from the ceiling lights seem more pronounced now, but I'm not sure if I like
> them that way.

Did you remember to add interiors with refractive indices to the materials?
Without that, the default IOR will be 1.0, which in fresnel mode gives 
no reflections at all.

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Cousin Ricky <ric### [at] yahoocom> wrote:
> On 2021-08-16 12:58 PM (-4), Chris R wrote:
> >
> > This was my first crack at updating the scene to use fresnel reflections.  I'm
> > not entirely happy with it, so I am rerunning with some different min/max
> > reflection values for the pool table.  I noticed the highlights on the table
> > from the ceiling lights seem more pronounced now, but I'm not sure if I like
> > them that way.
>
> What value are you using for reflection?  It should be reflection { 1
> fresnel } conserve_energy for the picture window, and close to 1 for the
> balls and table, unless you want reduced gloss.
>
> What value are you using for phong/specular?  At full gloss with an IOR
> of 1.5, Fresnel reflection varies from 0.04 to 1.00, depending upon
> angle of reflection.  I find that a value of specular albedo 0.05
> normally works well; you can use this on the balls.  However, with much
> of the table at a shallow reflection angle--85 degrees, I'm
> guessing--reflection is around 0.6.  Try specular albedo 0.6 or phong
> albedo 0.6 on the table, since the highlights are mostly on the top; but
> if you still get strong highlights on the side of the table, you may
> have to use an aoi texture with two different phong or specular values.
> For the picture window, of course, you would use the minimum 0.04.
>
> Always use the albedo keyword with phong and specular, so you can easily
> align your highlight level with the reflection level, and not have to
> worry about tweaking the highlights every time you change phong_size or
> roughness.
>
> The layered texture trick I posted above simulates the 3.8 improvements
> in Fresnel reflection on opaque objects.  If you use this trick, use it
> only for the balls and the table; do not use it for the picture window.
>
> If you want only half gloss on the balls or table, reduce the highlight
> by half, for example:
>
>   #version 3.7;
>   finish
>   { reflection { 0.5 fresnel } conserve_energy
>     specular albedo 0.025 // texture for balls and side of table
>     specular albedo 0.3 // texture for top of table
>   }
>
> Things get much easier with POV-Ray 3.8, no layered textures necessary:
>
>   #version 3.8;
>   finish
>   { fresnel 1
>     reflection { 1 } conserve energy
>     specular albedo 1 // works for balls, table, and window!
>   }
>
> Or, for half gloss:
>
>   #version 3.8;
>   finish
>   { fresnel 0.5
>     reflection { 0.5 } conserve energy
>     specular albedo 0.5 // works for balls and table
>   }

Here is the material I am using for the pool balls now:
    material {
        texture { _t }
        texture { pigment { color rgbf 1 }
            finish {
                specular albedo 0.025
                roughness 0.002
                reflection {
                    0.5
                    fresnel on
                }
                conserve_energy
            }
        }

        interior { _i }
    }
(texture { _t } is a solid color pigment)

I have attached a view of the balls with the overhead light viewed from a low
angle using this material.  I also tried specular 0.05, roughness 0.001 in
different combinations.  I can upload those if interested.



-- Chris R

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