{=============================================================================}
{= Copyright (c) Mark J. Kilgard, 1994.                                      =}
{=============================================================================}

{=============================================================================}
{= (c) Copyright 1993, 1994, Silicon Graphics, Inc.                          =}
{= ALL RIGHTS RESERVED                                                       =}
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{= written prior permission.                                                 =}
{=                                                                           =}
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{=                                                                           =}
{= US Government Users Restricted Rights                                     =}
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{=                                                                           =}
{= OpenGL(TM) is a trademark of Silicon Graphics, Inc.                       =}
{=============================================================================}
unit Stencil;

interface

implementation

uses
    MGLTypes,
    MGLGl,
    MGLGlut,
    MGLGlu,
    DemoList,
    CmdLine;

const
    YELLOWMAT   = 1;
    BLUEMAT     = 2;

procedure   MyInit;
const
    yellow_diffuse  : array[0..3] of GLfloat = ( 0.7, 0.7, 0.0, 1.0 );
    yellow_specular : array[0..3] of GLfloat = ( 1.0, 1.0, 1.0, 1.0 );

    blue_diffuse    : array[0..3] of GLfloat = ( 0.1, 0.1, 0.7, 1.0 );
    blue_specular   : array[0..3] of GLfloat = ( 0.1, 1.0, 1.0, 1.0 );

    position_one    : array[0..3] of GLfloat = ( 1.0, 1.0, 1.0, 0.0 );
begin
    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($0);
    glEnable(GL_STENCIL_TEST);
end;

// Draw a sphere in a diamond-shaped section in the
// middle of a window with 2 tori.
procedure   Display; cdecl;
begin
    glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);

    // draw blue sphere where the stencil is 1
    glStencilFunc (GL_EQUAL, $1, $1);
    glCallList (BLUEMAT);
    glutSolidSphere (0.5, 15, 15);

    // draw the tori where the stencil is not 1
    glStencilFunc (GL_NOTEQUAL, $1, $1);
    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);
    glutSolidTorus (0.275, 0.85, 15, 15);
    glPushMatrix();
        glRotatef (90.0, 1.0, 0.0, 0.0);
        glutSolidTorus (0.275, 0.85, 15, 15);
    glPopMatrix();
    glPopMatrix();
end;

// Whenever the window is reshaped, redefine the
// coordinate system and redraw the stencil area.
procedure   MyReshape(w, h: int); cdecl;
begin
    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, $1, $1);
    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, w/h, 3.0, 7.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef(0.0, 0.0, -5.0);
end;

// Main Loop
// Open window with initial window size, title bar,
// RGBA display mode, and handle input events.
procedure   Demo;
begin
    InitGLUT;
    glutInitDisplayMode (GLUT_SINGLE or GLUT_RGB or GLUT_DEPTH or GLUT_STENCIL);
    glutInitWindowSize (400, 400);
    glutCreateWindow ('Stencil');
    MyInit ();
    glutReshapeFunc (MyReshape);
    glutDisplayFunc(Display);
    glutMainLoop();
end;

initialization
    RegisterDemo(
                 'Book',   
                 'Stencil',
                 '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.',
                 Demo
                );
end.
