kue/disc.cpp


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#include <GL/gl.h>
#include <GL/glu.h>

#include <math.h>

#include "disc.h"

// The pre-allocated number of our display list
const int DISC_DISPLAY_LIST = 3;
// The disc radius currently cached in our display list
double disc_list_radius = 0.0;

void disc::draw(double x, double y, double r)
{
    glPushMatrix();

    // Move to the specified location
    glTranslatef(x, y, 0.0001);

    // Have we cached this radius
    if ((r == disc_list_radius) && (glIsList(DISC_DISPLAY_LIST) == GL_TRUE))
    {
        // Yes, just call the display list
        glCallList(DISC_DISPLAY_LIST);
    }
    else
    {
        // Nope, make a new quadric object
	GLUquadricObj *quad = gluNewQuadric();

        // Make a new display list
	glNewList(DISC_DISPLAY_LIST, GL_COMPILE_AND_EXECUTE);
        // Draw the disc
	gluDisk(quad, 0.0, r, 10, 1);
        // End the display list
	glEndList();

        // Update the cached value
        disc_list_radius = r;

        // Delete the quadric object
	gluDeleteQuadric(quad);
    }
 
    glPopMatrix();
}