Warp <war### [at] tagpovrayorg> wrote:
> Trevor G Quayle <Tin### [at] hotmailcom> wrote:
> > 1) System variables to return the resolution of an input image.  This appears to
> > be already available in the source code, just not passed on to the SDL.
>
>   This should definitely be doable, but I'll have to ask the team about
> their opinion. (Cons: Minor feature, increases reserved keyword clutter...)

This I understand, and it is something that maybe a lot of users wouldn't use.
Personally I have had a couple of situations where it could be of use lately.

> > 2) Separate ior for fresnel reflection (in finish block) to allow for better
> > texture mapping.
>
>   It indeed seems a bit strange that given that reflection is a property of
> the texture and not the interior, it would use a value from the interior.
> (I don't know the details of the theory behind fresnel reflection, but
> I could easily imagine a surface having a different ior on a thin reflecting
> layer on its surface than in its main body, thus causing a different type of
> reflection than an uniform object would have...)
>
>   Someone who knows the theory behind fresnel reclection could express his
> opinion on this.
>
> --
>                                                           - Warp

Well there is a relationship between the refraactive ior and fresnel reflection
(it's a bit more complex than presented, literally, as a complex number
component is involved, at least from my limited understanding).  It does indeed
seem a propery that is applicable to the interior workings of a material, so I
can see whay it it is outside the texture block, however, the capability for
texture mapping (with reflection being a texture property) would infer that if
ior is related to fresnel, which is related to texture, then ior should be
texture level.  So the solution would be either:
1) move ior to texture.  This would likely be the simplest to achieve (other
than backward compatibility considerations) And also give the side effect of
being extended to refraction for artistic effect.
2) add an additional ior for fresnel refraction only.  This would add a reserved
keyword and require the splitting of the usage of ior for refraction and
reflection.

Alternatively a third option would be:
3) Leave everything as is and make me use a different technique to achieve my
results.  (it is only a suggestion, so I don't fully expect it to be added at
this stage in the beta development)

All-in-all, perhaps the fresnel model needs to be examined a little closer for
better implementation in POV4.

Thanks for the consideration regardless.

-tgq

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