[gl2ps] gl2psBegin(End)Viewport usage

[Christophe Geuzaine]

> On 18 Apr 2015, at 21:33, Pantxo Diribarne <pantxo.diribarne at gmail.com> wrote:
> 
> Hi,
> 
> In GNU Octave we are trying to mimic the effect of "glClear (GL_DEPTH_BUFFER_BIT)", which is basically write subsequent primitives over previous ones disregarding their z depth,  using "gl2psEnd(Begin)Viewport" (see [1]). This works great on some machines but fails on others (some win7, see [2]) accompanied with a warning:
> "GL2PS warning: Unknown token in buffer"
> 
> Here is approximately what we do:
>  GLint ret = gl2psBeginPage (... | GL2PS_USE_CURRENT_VIEWPORT ...);
>  // draw
>  ...
>  // A new axes should be drawn over previous objects:
>  GLint vp[4];
>  gl2psEndViewport ();
>  glGetIntegerv(GL_VIEWPORT, vp);
>  gl2psBeginViewport (vp);
>  ...
>  glClear (GL_DEPTH_BUFFER_BIT);
>  // draw
>  ...
>  state = gl2psEndPage ();
> 
> Is it the way viewports are supposed to be used in gl2ps, or is there a better method to achieve what we want?
> 

A priori, yes. I have never personally used them for this purpose, though...

Christophe 

> Thanks in advance,
> 
> Pantxo
> 
> [1] https://savannah.gnu.org/bugs/?44806
> [2] https://savannah.gnu.org/bugs/?44765
> 
> 
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

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