Mixed projections

OpenGL OpenGL: Basic Coding
1

Hi,

is it possible to first draw objects in perspective mode, and then switch this view with gluOrtho2D and draw other objects, like controlbars etc…

in my RenderScene procedure, after drawing 3D, i would switch like this:

glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
gluOrtho2D(0, viewWidth, viewHeight, 0);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glPushAttrib(GL_ENABLE_BIT);
glDisable(GL_LIGHTING);
glDisable(GL_DEPTH_TEST);
glEnable(GL_TEXTURE_2D);
glEnable(GL_SCISSOR_TEST);

// i write my drawing code here

glDisable(GL_TEXTURE_2D);
glPopAttrib();
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

why doesn’t this work?

anybody?

2

wang the stuff to switch between them in some display lists (I’m using Persp & Ortho). Do this when your window is resized

{
glDeleteLists(Persp,1);
glDeleteLists(Ortho,1);
Persp = glGenLists(1);
Ortho = glGenLists(1);
if( h==0 ) h = 1;
glNewList(Persp,GL_COMPILE);
glViewport(0, (GLsizei) 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(55.0, w/h , 0.01, 500 );
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glEndList();

glNewList(Ortho,GL_COMPILE);
  glViewport(0, (GLsizei) 0, (GLsizei) w, (GLsizei) h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0, w, h, 0, -1, 1);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
glEndList();

}

Once thats done, your display func should be something of the form…

{
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT )
glLoadIdentity()
glCallList(Persp);

//draw 3d stuff

glCallList(Ortho);

//draw 2d gubbins

}

3

thanx a lot!