Mario Veraart (rioj7++at++fel.tno.nl)
Tue, 28 Oct 1997 15:23:43 +0100 (MET)
> - Using OpenGL to write pixels directly each frame
Could be done is not portable to IRISGL platforms
> Jukka Väisänen vaizki++at++iscape.fi
> Iscape Software http://www.iscape.fi/
Mario
-----------------------------------------------
Subject: Re: HUD problems; how to use OpenGL?
From: "Fred Clyne" <fred++at++octave.cambridge.com>
Date: Sat, 3 Aug 1996 18:47:31 -0400
Funny you should ask, I just did this today.
I am working in C but you should be able to translate. Also, this works
for both IrisGL and OpenGL. In the draw callback, after you render the
scene, add your call to the HUD function:
void MyDraw(pfChannel *chan, void *data)
{
pfClearChan(chan);
pfDraw();
DrawHUD();
}
The HUD drawing routine needs to set its perspective matrix with an
ortho command and the viewing matrix with some matrix commands. I
had trouble with the different coordinate systems being used, so be
careful. The scene is in Performer coordinates (z-up, y-away, x-right).
So I created my HUD with z and x coords to be "consistent".
I put my data in gsets and created an ortho frustum that I remember in
the shared data structure along with DCS nodes to move things around on
the HUD. I also didn't wory about saving the perspective matrix since
the HUD is drawn last and the matrix will be set again by the channel.
at init time:
frust = pfNewFrust(arena);
pfFrustNearFar(frust,-1.0f,1.0f);
pfMakeOrthoFrust(frust,left,right,bottom,top);
sharedData->frust = frust;
..
sharedData->numGsets = nn;
sharedData->gsetList[0] = ...
sharedData->dcsList[0] = ...
APP updates the DCS nodes each frame:
pfDCSRot(sharedData->dcsList[0],...
void DrawHUD(void)
{
pfMatrix mat;
int ii;
/* work in my own graphics state */
pfPushState();
pfBasicState();
/* turn of the zbuffer so this always shows on top */
#ifdef IRISGL
zbuffer(FALSE);
#else
#ifdef OPENGL
glDisable(GL_DEPTH_TEST);
#else
...Please Define IRISGL/OPENGL...
#endif
#endif
/* create the ortho projection */
pfApplyFrust(sharedData->frust);
/* set the view matrix - push a GL ident matrix on stack */
pfPushIdentMatrix();
/* rotate back to Perf coords */
pfRotate(PF_X,-90.f);
/* draw the HUD */
for (ii=0; ii<sharedData->numGsets; ++ii)
{
pfPushMatrix();
pfGetDCSMat(sharedData->dcsList[ii],mat)
pfMultMatrix(mat);
pfDrawGSet(sharedData->gsetList[ii]);
pfPopMatrix();
}
/* restore the view matrix */
pfPopMatrix();
/* restore zbuffer testing */
#ifdef IRISGL
zbuffer(TRUE);
#else
#ifdef OPENGL
glEnable(GL_DEPTH_TEST);
#else
...Please Define IRISGL/OPENGL...
#endif
#endif
/* restore the graphics state */
pfPopState();
}
Hope this helps.
--Fred Clyne
Cambridge Research Associates office: 703-790-0505 x 7211 1430 Spring Hill Road, Suite 200 fax: 703-790-0370 McLean, VA 22102 email: fred++at++cambridge.com
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