save current window drawing before clear?

[Loderunner]

So I have a collection of different trignometric shapes being drawn and updated constantly. I just incorporated a panning-zoom out system from http://www.nigels.com/glt/gltzpr/

The problem is that to pan properly I need to call
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
If the clear isn't called the drawing is just copied onto itself.
If clear IS called then the drawing keeps clearing and only drawing the newest part (think of a 2d map that only displays the newest segment and location instead of the previous history)

Is there a way to save the entire current image and then run the clear so that the image can be panned?
Thanks,

[ZbuffeR]

hmm you want to both clear and keep the current framebuffer ? make up your mind

[Loderunner]

Well, this is what happens when i dont clear:
http://img708.imageshack.us/img708/2...reenshot1w.png

I want to be able to move the image while clearing the old image. Was wondering if there was a way to save the current data somewhere and move it, clearing the old data.

[ZbuffeR]

glCopyTexSubImage2d the current framebuffer to a texture, then render the texture at a different place.

[Loderunner]

Hmm, I dont think that this would really help me.
Here are selected pieces of code:

//Initialize GLUT
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowSize(600, 600);
 
	//Create the window
	glutCreateWindow("2D map");
	glutDisplayFunc(display);
	//
	/*------init panning-------------*/	
	zprInit();
    	zprSelectionFunc(drawScene);     /* Selection mode draw function */
    	zprPickFunc(pickScene);        
	/*------end panning--------------*/
glutTimerFunc(100, update, 0); //Add a timer

void display(void)
{
	/* Initialise OpenGL Lighting and material structure */
	GLERROR;
	glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
	glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
	glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
	glLightfv(GL_LIGHT0, GL_POSITION, light_position);
 
	glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
	glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
	glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
	glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);
 
	glEnable(GL_LIGHTING);
	glEnable(GL_LIGHT0);
	glDepthFunc(GL_LESS);
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_NORMALIZE);
	glEnable(GL_COLOR_MATERIAL);
	GLERROR;
   	//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glClear(GL_DEPTH_BUFFER_BIT);
	drawScene();
	glutSwapBuffers();
 
	GLERROR;
}

void drawScene(void) {
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	//glClear(GL_DEPTH_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW); //Switch to the drawing perspective
	//glLoadIdentity(); //Reset the drawing perspective
 
	glPushMatrix();
	glTranslatef(0.0f, 0.0f, -5.0f); //Move forward 5 units into visible region
 
 
 
	if((prevcoord[0]!=coordinates[0])&&(prevcoord[1]!=coordinates[1])){ //this if statement accounts for transmission lag
		glPushMatrix(); //Save the current state of transformations
		glPushName(1);
			glColor3ub(255,255,255); //white
			glBegin(GL_LINE_STRIP);	
				glVertex3f(prevcoord[0],prevcoord[1],prevcoord[2]);//initial line co-ordinate, needs to be updated to init GPSlocation
				glVertex3f(coordinates[0],coordinates[1],coordinates[2]);				
			glEnd();
		glPopName();
		glPopMatrix();
 
 
	//draws the red triangle with the current location of the igv
	glPushMatrix();	 //save previous translate and color
	glPushName(2);
		//glClear(GL_DEPTH_BUFFER_BIT);	
		glTranslatef(coordinates[0],coordinates[1],coordinates[2]);
		glRotatef((360/(2*PI))*atan2(coordinates[1],coordinates[0]),coordinates[0],coordinates[1],coordinates[2]); //does rotation calc
		//glRotatef((360/(2*PI))*atan2(coordinates[1],coordinates[0]),1,1,1); //does rotation calc
		glColor3ub(255,0,0); //set to red	
		glBegin(GL_TRIANGLES);
			glVertex2f(0,.05);				
			glVertex2f(0,-.05);
			glVertex2f(.05,0);
		glEnd();
	glPopName();
	glPopMatrix(); //restore previous translate and color
	}
 
	//this section erases the old triangle and overwrites it with a green dot
	if((prevcoord[0]!=coordinates[0])&&(prevcoord[1]!=coordinates[1])){	//this if statement accounts for transmission lag
		glPushMatrix();	 //save previous translate and color
		glPushName(3);
			glTranslatef(prevcoord[0],prevcoord[1],prevcoord[2]);
			glRotatef((360/(2*PI))*atan2(prevcoord[1],prevcoord[0]),prevcoord[0],prevcoord[1],prevcoord[2]);
			//glRotatef((360/(2*PI))*atan2(prevcoord[1],prevcoord[0]),1,1,1);
			glColor3ub(0,0,0); //set black	
			glBegin(GL_TRIANGLES);
				glVertex2f(0,.05);				
				glVertex2f(0,-.05);
				glVertex2f(.05,0);
			glEnd();
			glColor3ub(0,255,0); //set sphere to green
			glutSolidSphere(.02,15,15); //radius, slices,stacks
		glPopName();
		glPopMatrix(); //restore previous translate and color
	}
	glPopMatrix();
	glutSwapBuffers();
}

Any suggestions?

[Loderunner]

notice this specific line:

   	//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glClear(GL_DEPTH_BUFFER_BIT);

if glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
is uncommented then it pans properly but only draws one line segment, one triangle and one green dot and erases the previous history

[Loderunner]

any suggestions anyone? =)