Re: Explicit color for pm3d

[Ethan A M. <sf...@us...>]

Douglas Mason <dou...@gm...> wrote>
> 
> Let's say you have a surface. It should be trivial to calculate the gradient
> at any point in the surface by simply calculating the difference to each
> neighboring point.

Not exactly trivial, but yes it could be done.

> Based on the technique of normal maps, you can create a function that simply
> adds or subtracts light (i.e., each RGB channel in unison) based on the
> angle of the gradient. Or simply provide said normal map which has its own
> uses.

I take it you are thinking of Gouraud shading, but that's not how it works.
The normal at each vertex is used to calculate a different shading at each
pixel within the face bounded by those vertices.  But gnuplot cannot draw
pixel-by-pixel; it draws the entiry face in one go.  So differential shading
across the face is not possible.

> This would permit a perfectly usable bump map in gnuplot

A bump map is something else again.  But again this results in a per-pixel
color distinction.  So - nice idea, but not in gnuplot.

	Ethan