(cc grass5)
On Sat, Jul 20, 2002 at 10:18:34PM +0200, Johannes Bühler wrote:
thats probably the best idea. but not very elegant. so that is way i was
looking for a more smartly way to solve this problem.
thanks.
In general there should be a function in OpenGL to draw filled
polygons which needs to be implemented in NVIZ.
Does anyone know details how to fill vector polygons with OpenGL?
Markus
On Sat, 20 Jul 2002 19:46:45 +0100 (BST)
Paul Kelly <paul-grass@stjohnspoint.co.uk> wrote:
> I think you could convert the vector layer containing the labelled
> polygons to a raster, using v.to.rast, and display that. You might have to
> use r.colors or something to make sure the lakes come out blue or whatever
> colour you need. The rest of the raster layer would be null so it would be
> transparent in NVIZ I think (haven't tried this)
>
> On Sat, 20 Jul 2002, Johannes Bühler wrote:
>
> > hi,
> > does anyone know if it is possible to show filled polygons (lakes) in nviz.
> >
> > thanks
> > Johannes Buehler
> >
> > --
> > -- Johannes Buehler
> > __O Feldtstr. 45
> > =`\<, 14789 Greifswald
> > (=)/(=) johannesbuehler@oderbruecke.de
> > -----------
Markus Neteler wrote:
(cc grass5)
On Sat, Jul 20, 2002 at 10:18:34PM +0200, Johannes Bühler wrote:
> thats probably the best idea. but not very elegant. so that is way i was
> looking for a more smartly way to solve this problem.
> thanks.
In general there should be a function in OpenGL to draw filled
polygons which needs to be implemented in NVIZ.
Does anyone know details how to fill vector polygons with OpenGL?
Markus
>
> On Sat, 20 Jul 2002 19:46:45 +0100 (BST)
> Paul Kelly <paul-grass@stjohnspoint.co.uk> wrote:
>
> > I think you could convert the vector layer containing the labelled
> > polygons to a raster, using v.to.rast, and display that. You might have to
> > use r.colors or something to make sure the lakes come out blue or whatever
> > colour you need. The rest of the raster layer would be null so it would be
> > transparent in NVIZ I think (haven't tried this)
> >
> > On Sat, 20 Jul 2002, Johannes Bühler wrote:
> >
> > > hi,
> > > does anyone know if it is possible to show filled polygons (lakes) in nviz.
> > >
> > > thanks
> > > Johannes Buehler
> > >
> > > --
> > > -- Johannes Buehler
> > > __O Feldtstr. 45
> > > =`\<, 14789 Greifswald
> > > (=)/(=) johannesbuehler@oderbruecke.de
> > > -----------
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Markus,
The current vector drawing is handled by the ogsf library calls
gsd_bgnline and gsd_endline. The gsd_bgnline initializes the OpenGL call
to glBegin(GL_LINE_STRIP). This simply draws a connected group of line
segments. Note that this is the same routine that draws the wire frame
surface.
To draw a filled polygon you could use something like
glBegin(GL_POLYGON). This would require paying attention to the vertices
passed to the function to make sure it closes the way you want.
Note that the shaded surface is drawn with a more complex call to
glBegin(GL_TRIANGLE_STRIP).
I will take a look to see how easy (or not) implementing closed polygons
might be.
Hope this helps.
--
Bob Covill
Tekmap Consulting
P.O. Box 2016
Fall River, N.S.
B2T 1K6
Canada
E-Mail: bcovill@tekmap.ns.ca
Phone: 902-860-1496
Fax: 902-860-1498
Markus Neteler wrote:
> thats probably the best idea. but not very elegant. so that is way i was
> looking for a more smartly way to solve this problem.
> thanks.
In general there should be a function in OpenGL to draw filled
polygons which needs to be implemented in NVIZ.
Does anyone know details how to fill vector polygons with OpenGL?
Filling a polygon is easy: glBegin(GL_POLYGON). However, in OpenGL, a
"polygon" is planar and convex. To fill a non-convex region, you need
to use the GLU tesselator API.
Also, if you wish to "drape" a vector area map over a surface, you
need to cut the region into a mesh of smaller regions along the
surface's grid lines.
--
Glynn Clements <glynn.clements@virgin.net>