/*
 * (c) Copyright 1993, Silicon Graphics, Inc.
 *               1993-1995 Microsoft Corporation
 *
 * ALL RIGHTS RESERVED
 *
 * Please refer to OpenGL/readme.txt for additional information
 *
 */

/*  stencil.c
 *  This program draws two rotated tori in a window.  
 *  A diamond in the center of the window masks out part 
 *  of the scene.  Within this mask, a different model 
 *  (a sphere) is drawn in a different color.
 */
#include "glos.h"

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

void myinit(void);
void CALLBACK display(void);
void CALLBACK myReshape(GLsizei w, GLsizei h);

#define YELLOWMAT   1
#define BLUEMAT 2

void myinit (void) 
{
    GLfloat yellow_diffuse[] = { 0.7, 0.7, 0.0, 1.0 };
    GLfloat yellow_specular[] = { 1.0, 1.0, 1.0, 1.0 };

    GLfloat blue_diffuse[] = { 0.1, 0.1, 0.7, 1.0 };
    GLfloat blue_specular[] = { 0.1, 1.0, 1.0, 1.0 };

    GLfloat position_one[] = { 1.0, 1.0, 1.0, 0.0 };

    glNewList(YELLOWMAT, GL_COMPILE);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, yellow_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, yellow_specular);
    glMaterialf(GL_FRONT, GL_SHININESS, 64.0);
    glEndList();

    glNewList(BLUEMAT, GL_COMPILE);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, blue_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, blue_specular);
    glMaterialf(GL_FRONT, GL_SHININESS, 45.0);
    glEndList();

    glLightfv(GL_LIGHT0, GL_POSITION, position_one);

    glEnable(GL_LIGHT0);
    glEnable(GL_LIGHTING);
    glDepthFunc(GL_LESS);
    glEnable(GL_DEPTH_TEST);

    glClearStencil(0x0);
    glEnable(GL_STENCIL_TEST);

}

/*  Draw a sphere in a diamond-shaped section in the
 *  middle of a window with 2 tori.
 */
void CALLBACK display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

/* draw blue sphere where the stencil is 1 */
    glStencilFunc (GL_EQUAL, 0x1, 0x1);
    glCallList (BLUEMAT);
    auxSolidSphere (0.5);

/* draw the tori where the stencil is not 1 */
    glStencilFunc (GL_NOTEQUAL, 0x1, 0x1);
    glStencilOp (GL_KEEP, GL_KEEP, GL_KEEP);
    glPushMatrix();
    glRotatef (45.0, 0.0, 0.0, 1.0);
    glRotatef (45.0, 0.0, 1.0, 0.0);
    glCallList (YELLOWMAT);
    auxSolidTorus (0.275, 0.85);
    glPushMatrix();
        glRotatef (90.0, 1.0, 0.0, 0.0);
        auxSolidTorus (0.275, 0.85);
    glPopMatrix();
    glPopMatrix();
    glFlush();
}

/*  Whenever the window is reshaped, redefine the 
 *  coordinate system and redraw the stencil area.
 */
void CALLBACK myReshape(GLsizei w, GLsizei h)
{
    h = (h == 0) ? 1 : h;
    glViewport(0, 0, w, h);

    glClear(GL_STENCIL_BUFFER_BIT);
/* create a diamond shaped stencil area */
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-3.0, 3.0, -3.0, 3.0, -1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glStencilFunc (GL_ALWAYS, 0x1, 0x1);
    glStencilOp (GL_REPLACE, GL_REPLACE, GL_REPLACE);
    glBegin(GL_QUADS);
    glVertex3f (-1.0, 0.0, 0.0);
    glVertex3f (0.0, 1.0, 0.0);
    glVertex3f (1.0, 0.0, 0.0);
    glVertex3f (0.0, -1.0, 0.0);
    glEnd();

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0, (GLfloat) w/(GLfloat) h, 3.0, 7.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef(0.0, 0.0, -5.0);
}

/*  Main Loop
 *  Open window with initial window size, title bar, 
 *  RGBA display mode, and handle input events.
 */
int main(int argc, char** argv)
{
    auxInitDisplayMode (AUX_SINGLE | AUX_RGB 
    | AUX_DEPTH16 | AUX_STENCIL);
    auxInitPosition (0, 0, 400, 400);
    auxInitWindow ("Stencil Test");
    myinit ();
    auxReshapeFunc (myReshape);
    auxMainLoop(display);
    return(0);
}
