Wireframe rendering (that's fast in software)?

Wireframe rendering (that's fast in software)?

Post by Patrick Madd » Wed, 28 May 1997 04:00:00



My machine doesn't have hardware acceleration, so I'd like to be
able to switch between shaded and wireframe/non-depth-buffered
renders.  Right now, the shaded render is too slow for interactive
work (and I don't think it's the vertex transform time--I have an
X11 app that does wireframe, and it's much faster than OpenGL).

I've switched the polygon state to non-filled, but I suspect it's
still checking the depth buffer.  Render times are roughly equal for
filled and non-filled.  I'm working with Mesa+Linux, but would like a
solution that's portable to windoze and other unix boxes.

Thanks for any help,

Patrick

 
 
 

Wireframe rendering (that's fast in software)?

Post by Michael I. Gol » Wed, 28 May 1997 04:00:00


| I've switched the polygon state to non-filled, but I suspect it's
| still checking the depth buffer.  Render times are roughly equal for
| filled and non-filled.  I'm working with Mesa+Linux, but would like a
| solution that's portable to windoze and other unix boxes.

Changing PolygonMode doesn't affect whether or not depth testing is
performed.  If you wish to disable depth testing, you must:

        glDisable(GL_DEPTH_TEST);

Also for wireframe rendering you may wish to disable smooth shading:

        glShadeModel(GL_FLAT);

and disable lighting:

        glDisable(GL_LIGHTING);

In general you should turn off any operations which are not necessary
for your current rendering mode.

This being said, I should also point out that some systems actually
render shaded polygons faster than wireframe, presumably because all
optimization efforts were focused on shading.

--
Michael I. Gold     Silicon Graphics Inc.     http://www.veryComputer.com/
And my mama cried,  "Nanook a no no! Don't be a * eskimo! Save your
money, don't go to the show!"  Well I turned around and I said, "Ho! Ho!"