Re: bug in depthorder?

[Petr M. <mi...@ph...>]

> > The enclosed script using the "pm3d depthorder" gives wrong ordering of
> > faces on gnuplot-cvs, and sometimes wrong and sometimes good ordering on
> > gnuplot 4.2. Also try to rotate the plot by mouse. How can this happen?
> 
> Petr,
> 
> depthorder is a very much an approximation to true hidden surface features.  I
> think there was some discussion a couple years ago about this.  If I'm
> remembering correctly, I wrote a patch for determining the depth which I
> thought was a bit more robust.  But after discussions with Ethan, I thought it
> would be more worthwhile putting effort into actual hidden surface, if one had
> time.  (A generalization of the hidden lines code where a hidden surface is
> broken into smaller parts.)
> 
> The problem in your example is that the surfaces are too big relative to the
> resolution such that in 3D space their depths overlap.  Furthermore, this
> example is probably undersampling anyway because the peaks aren't visible.

I was wondering which point(s) of the rectangle is/are used for the depth 
ordering. Is it min(all 4 corners) or center-of-rectangle or all of them? It 
seems to me that this is producing this bug: the two problematic rectangles 
touch in one edge (2 corners), but their other 2 corners have different 
depth.

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PM