"SharkD" <nomail@nomail> wrote in message
> ... snip ...
> I'd like the grid lines to exist /within/ the sphere, as well as on the 
> surface.
> Currently, if I cut a corner away from the sphere, the cut-away portion is
> completely opaque (dark green in this case, black if I use Trevor G 
> Quayle's
> code).
>

Actually I think the grid lines do exist within the sphere and I suspect 
that this is why you get a green or black surface in your cut-away. If the 
cut surfaces align with a horizontal line (eg. latitude 0 degrees) and two 
of the longitudinal lines (e.g. 0 and 90 degrees) then you'll get the colour 
of the grid lines (assuming you apply the one texture to the whole object).

One way of resolving that would be to shift the horizontal lines up by half 
the current separation and rotate the sphere around the vertical axis by 
half a segment. Another would be to specify an appropriate texture of your 
choice to the object doing the cutting. e.g. a displaced and rotated 
gridline texture combined with an onion texture to give you the concentric 
spheres.

> It's a personal request. I'd like to replace the SVG image with a nicely
> rendered one, as the SVG image was removed from an article for being "too 
> ugly"
> (kind of a stupid reason to remove a diagram from an encyclopedia, but
> anyway...).
>

If it's an ugliness problem then presumably you don't want to just reproduce 
something that's very similar to what you've got. Also, I agree with Nicolas 
that a rendered image with grid-lines wouldn't scale as well as a vector 
graphics image will, resulting in less clarity and potentially some of the 
lines disappearing as it gets scaled down or uneven thickening as it gets 
scaled up. You may want to consider keeping the lines from the existing SVG 
file overlayed on top of prettier bitmapped spheres.

You could probably do smoothly graded spheres in POV-Ray using orthographic 
projection and only ambient lighting, but I thought it was also possible to 
do such colour grading in an SVG editor.

Hope there's something in all that that's helpful.

Regards,
Chris B.

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