How to draw a screen aligned QUAD?

OpenGL OpenGL: Basic Coding
1

if i initialize the Viewport like this:

glViewport(0, 0, screenWidth, screenHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0f, (float)(screenWidth)/screenHeight, 1.0f, 100.0f);
glMatrixMode(GL_MODELVIEW);
2

Hi,
You will need to use the orthographic projection for this. Something along these lines should work.


void OnResize(int nw, int nh) {
   glViewport(0,0,nw,nh);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(0,1,0,1,0,1);
   glMatrixMode(GL_MODELVIEW);
}

Then use this code to draw the quad


void DrawFullScreen() {
   glBegin(GL_QUADS);
      glVertex2f(0,0);
      glVertex2f(1,0);
      glVertex2f(1,1);
      glVertex2f(0,1);
   glEnd();
}

See if this helps.

3

Here’s another one


void OnResize(int nw, int nh) {
   glViewport(0,0,nw,nh);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glMatrixMode(GL_MODELVIEW);
}



void DrawFullScreen() {
   glBegin(GL_QUADS);
      glVertex2f(-1,-1);
      glVertex2f(1,-1);
      glVertex2f(1,1);
      glVertex2f(-1,1);
   glEnd();
}