GLdc/GL/glu.c

#include <math.h>
#include "private.h"

/* Set the Perspective */
void APIENTRY gluPerspective(GLfloat angle, GLfloat aspect,
                    GLfloat znear, GLfloat zfar) {
    GLfloat xmin, xmax, ymin, ymax;

    ymax = znear * tanf(angle * F_PI / 360.0f);
    ymin = -ymax;
    xmin = ymin * aspect;
    xmax = ymax * aspect;

    glFrustum(xmin, xmax, ymin, ymax, znear, zfar);
}

void APIENTRY gluOrtho2D(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top) {
    glOrtho(left, right, bottom, top, -1.0f, 1.0f);
}