perspective question

  

void ChangeSize(int w, int h)
	{



	GLfloat FAspect,
			nRange= 150.0f;


	// Prevent a divide by zero

	if(h == 0)
		h = 1;

	// Set Viewport to window dimensions

    glViewport(0, 0, w, h);

	FAspect = (GLfloat)w / (GLfloat)h;
	
	// Reset projection matrix stack

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	gluPerspective(60.0f,FAspect,-500.0f,500.0f);
/*
	// Establish clipping volume (left, right, bottom, top, near, far)
    if (w <= h) 
		glOrtho (-nRange, nRange, -nRange*h/w, nRange*h/w, -nRange, nRange);
    else 
		glOrtho (-nRange*w/h, nRange*w/h, -nRange, nRange, -nRange, nRange);
*/
	// Reset Model view matrix stack

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	}