Re: [Gnuplot-info] maxima + gnupolot: 3D rendering bug?

[Hans-Bernhard B. <HBB...@t-...>]

On 12.12.2010 20:10, Ethan Merritt wrote:

> Is it possible that instead of modifying the pm3d code, one could modify
> the hidden-surface removal code in hidden3d?   The hidden3d code is
> already finding all the relevant lines of intersection and occlusion.

Actually, no.  hidden3d deals with hidden _line_ removal, only.  It has 
no code whatsoever for either sorting or splitting triangles.

> At the end of the hidden3d calculation there is a collection of edges,
> each of which is either all or part of an edge from the original set
> of polygons or an intersection of two polygons.  At that point the code
> walks through the list and draws all the edges.

Again, not really.  hidden3d draws individual surviving segments 
immediately when they're discovered (in_front() calls draw_edge() 
itself).  There is no complete list of visible edge fragments in memory 
at any time.

> Does it track enough information to also call term->filled_polygon()
> for each facet?

It doesn't even try to track facets.  It tracks edge fragments, not 
polygon fragments.

> If not, could the data structures be expanded to hold that tracking
> information?

"Expanding" wouldn't really do describing the job justice. It'd be more 
of a complete rewrite.