[R] Re: Problems with rgl package

[Duncan Murdoch]

On Wed, 20 Mar 2002 08:38:59 +0100, you wrote:

>By the way, I would like to say that I really like rgl,... although there is
>no possibility to save the graph in a vector format like postscript or
>wmf/emf. Is it a limitation of OpenGl libraries?

OpenGL is a raster-oriented renderer.  RGL does maintain a
vector-oriented list of things to draw, but OpenGL does all the
hidden-object removal by maintaining a "z-buffer", i.e. an indicator
of the depth of each pixel in the scene.  It would be quite difficult
to reproduce that properly in Postscript or wmf/emf.  You could come
close by drawing things from the back to the front, but errors would
be made, e.g. when drawing intersecting polygons.

Duncan Murdoch
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