PDA

View Full Version : Mostly Basic Suggestions For OGL



Zorro
07-28-2000, 12:52 PM
I use OpenGL quite a bit on SGI's (IRIX) and
on PCs (NT). I'd call myself an intermediate
OpenGL user. My applications are in the
field of Aerospace Engineering Visualization.
One of my gripes with OGL is that it starts
at too high a level, i.e. you cannot display
anything in a window without mucking with
identity matrices, specifying a projection,
etc. A user should be able to plot, paint,
etc., in the pixel coordinates of his window
without having to mess around with 3D cord.
systems & clip planes. I would also like to
see (and have uses for) normals assigned to
points (points which are NOT vertices of
polygons). Normals assigned to vertices of
lines (not polys) would be useful. Finally,
I'd like to see Phong shading available as
a display option. Thanks.

Serge K
07-28-2000, 04:56 PM
> A user should be able to plot, paint, etc., in the pixel coordinates of his window without having to mess around with 3D cord. systems & clip planes.

I guess, you want something like GL_REND_screen_coordinates (http://oss.sgi.com/projects/ogl-sample/registry/REND/screen_coordinates.txt) , right?

> I would also like to see (and have uses for) normals assigned to points (points which are NOT vertices of polygons). Normals assigned to vertices of lines (not polys) would be useful

??? 8-/
And who prevents you to do it right now???

Zorro
07-30-2000, 06:31 AM
I am new to this forum. I didn't understand
your reply. For example, what is 'GL_REND_screen_coordinates'? I went to the
link. It seems to describe something similar
to one of my suggestions. Is this something
someone is working on? Is it in OGL 1.2?
(I'm using 1.1). Were you suggesting that
I write my own version of that function?
I could probably do that, but I still think
it should be something that is native to OGL
1.5 or 2.0, whatever the next version is
going to be.

Bob
07-30-2000, 07:26 AM
What SergeK was speaking about is called an extension. It's (as the name says) an extension to the standard functionality in OpenGL, i.e. nothing that is required, but rather something the vendors (who are making the drivers) might want to add. Not all vendors support this extension, and might not be available on your platform.

GL_REND_screen_coordinates is an extension that let you bypass the modelview- and projectionmatrix multiplication.

And no, this is nothing you can do on your own, beacause it's a driverissue. However, as with all extensions, you can always "approximate" the extension, in this case by setting a proper orthogonal projectionmatrix.

Extensions is a tad difficult to use since you cant just use them as a regular function. You must load them from memory on your own (if you are on a Win32-platform - dunno about X).

Serge K
07-30-2000, 10:58 PM
Zorro:
I am new to this forum. I didn't understand your reply.
Hmm, my reply contain nothing specific to this forum, period.

But I guess, I was misleaded by your message:
> I use OpenGL quite a bit on SGI's (IRIX) and on PCs (NT). I'd call myself an intermediate OpenGL user.