Problem rendering text with a 3d enviroment

OpenGL OpenGL: Basic Coding
1

Hi, I have a program with a 3d enviroment and wanted to put some 2d text up for debugging. I’ve tried implimenting the NeHe tutorial, but have came to a problem. If i render the text i see nothing but the text, and i dont know how to fix it. the problem seems to be changing the matrix mode to display the text, but changing back after drawing the text doesn’t work.

void DrawScene() 
{	
	char buffer[200];
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear Screen And Depth Buffer
//	glLoadMatrix(GL_MODELVIEW); // just to be safe
	glLoadIdentity();									// Reset The Current Modelview Matrix
	
	float sy = sin(yaw);
	float cy = cos(yaw);
	float sp = sin(pitch);
	float cp = cos(pitch);

				WWLA[0] = WWA[0] + sy * cp;
				WWLA[1] = WWA[1] - sp;
				WWLA[2] = WWA[2] + cy * cp;

gluLookAt(
    WWA[0],				//Where we're at
    WWA[1],
    WWA[2],
    WWLA[0],	//Where we're looking at (based on where we're at)
    WWLA[1],
    WWLA[2],
    0,					//Which direction is up
    1,
    0
);

	DrawModels();
	glTranslatef(0.0f, 0.0f, 0.0f);
	glCallList(terrainList);	



		glLoadIdentity();							// Reset The Current Modelview Matrix
	glMatrixMode(GL_PROJECTION);				// Go to projection mode
	glPushMatrix();								// Remember where we're at
	glDisable(GL_LIGHTING);
	glDisable(GL_TEXTURE_2D);
	// Pulsing Colors Based On Text Position
//	glColor3f(1.0f*float(cos(cnt1)),1.0f*float(sin(cnt2)),1.0f-0.5f*float(cos(cnt1+cnt2)));
	glColor4f(1.0f,0.0f,0.0f,1.0f);
	// Position The Text On The Screen
	sprintf(buffer, "blah blah blah");
	glRasterPos2f(-0.45f+0.05f*float(cos(cnt1)), 0.32f*float(sin(cnt2)));
	glPrint("Active OpenGL Text With NeHe - %7.2f", cnt1);	// Print GL Text To The Screen
	cnt1+=0.051f;										// Increase The First Counter
	cnt2+=0.005f;										// Increase The First Counter
	glEnable(GL_TEXTURE_2D);
	glEnable(GL_LIGHTING);
	glMatrixMode(GL_MODELVIEW);
	glPopMatrix();

	SwapBuffers(ghdc);// Swap the frame buffers.


//CheckMouse();	//Check for mouse input
	glFlush();

}

with glMatrixMode(GL_MODELVIEW) commented out i get the text but no models, with it not commented out i get no text but models. am i doing something wrong?

2

You’re pushing the projection matrix, and later pop the modelview matrix. You have to call glPopMatrix before you change the matrix mode back to GL_MODELVIEW.

3

callng pop matrix first didn’t work. i just get no text at all.

4

What’s your projection matrix ?

5

um…even though that was a straightforward question i dont understand it. to be honest, im not even that sure about projection matrix. i ‘think’ it dictates camera orientation but im not even sure about that, and even if i take that to be true im still not sure how to tell you what my projection matrix is.

6

Using glOrtho for your projection matrix might help.

glMatrixMode (GL_PROJECTION);
glOrtho (...);
glLoadIdentity();
// 2D texts here
glMatrixMode (GL_MODELVIEW);
// back to modelisation visualisation
7

i tried using ortho, but it doesn’t work. appears to clear to a black screen

glMatrixMode (GL_PROJECTION);
glOrtho(-50.0, 50.0, -50.0, 50.0, -1.0, 1.0);
glLoadIdentity();
// 2D texts here
glRasterPos2f(-0.45f+0.05ffloat(cos(cnt1)), 0.32ffloat(sin(cnt2)));
glPrint(“Active OpenGL Text With NeHe - %7.2f”, cnt1); // Print GL Text To The Screen

glMatrixMode (GL_MODELVIEW);

8

Linky
Have no time to type.