"Bald Eagle" <cre### [at] netscapenet> wrote:
> William F Pokorny <ano### [at] anonymousorg> wrote:
>
> > Assuming you want access to the real internally generated >first rays,
>
> Nope.
> Just something like:
>
> #declare SFn_vdot = function (ax, ay, az, bx, by, bz) {ax*bx + ay*by + az*bz}
>
> #declare f_Reflectionx = function (Dx, Dy, Dz, Nx, Ny, Nz) {Dx - 2 * SFn_vdot
> (Dx, Dy, Dz, Nx, Ny, Nz)* Nx}
> #declare f_Reflectiony = function (Dx, Dy, Dz, Nx, Ny, Nz) {Dy - 2 * SFn_vdot
> (Dx, Dy, Dz, Nx, Ny, Nz)* Ny}
> #declare f_Reflectionz = function (Dx, Dy, Dz, Nx, Ny, Nz) {Dz - 2 * SFn_vdot
> (Dx, Dy, Dz, Nx, Ny, Nz)* Nz}
>...

You are already thinking in the right ways...
To see how you can use that further, have a look here:

Subject: Source code for "With and without a light_source"
From: Tor Olav Kristensen
Date: 2003-06-23 18:20:41
https://news.povray.org/povray.text.scene-files/message/%3CXns93A54E262AE2torolavkhotmailcom%40204.213.191.226%3E

There's no vector cross expressions there. But that will require only 3 small
exressions.

--
Tor Olav
http://subcube.com
https://github.com/t-o-k

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