[PD] Gem - EPS parser

[Tom Schouten]

On Wed, 25 Aug 2004, IOhannes m zmoelnig wrote:

> timon botez wrote:
> > Scuse my ignorance. Im using the tex-object to build models and as far
> > as I understand, the text object draws polygons right? How about Gem
> > objects to OBJ's? The rest I can handle in Alias wavefront...
> >
> probably i have sent this mail to tim already; but i have lost it and
> just for the archives:
>
> the problem is a bit subtle.
> openGL is (to a wide extent) vector-based.
> Gem is openGL-based.
>
> however, Gem does not handle the vectors (vertices, polygons,...) itself
> (in very special cases it does so). instead, this is done by the
> openGL-server (which is done by the GPU on modern gfx-cards)
> e.g, Gem only tells the openGL-server to rotate an "object"; it does not
> do the calculations itself.
>
> openGL is optimized for a one-way connection (meaning: it is fast to
> send something to the openGL-server; but slow to get information back
> from the server); furthermore i don't even know, whether it is possible,
> to get the vector-information before it is passed to the rasterizer (the
> last stage of rendering: make pixels out of abstract polygons)
>
> of course it would be possible to do all the vector-transformations
> within Gem: this would be slow (as it had to be done on the CPU instead
> of the optimized GPU); AND this would mean a *lot* of re-programming of
> things that are already there.
>
> the forthcoming vertex-stuff (a starter is already in the CVS) will
> handle verteces directly in Gem most of the time
> an object-exporter will most probably make sense here.
>
>

just a small remark.

it think it is possible to directly map opengl to postscript, by just
mapping the initial data (coordinates, model, ...) and the operations
(rotate, translate) to postscript code.

i think there's no 'native' support in postscript for 3d objects (just
2d). anyway, wether anyone would want to invest time in this is another
question. postscript is very flexible, but really a pain to use directly.
and doing a full mapping is quite a lot of work i think, but definitely
possible.

actually, i would be surprized if there isn't any code for this floating
around on the internet, maybe using some intermediate format.. so many
crazy people out there :)