TEA.C

/* 
 * (c) Copyright 1993, Silicon Graphics, Inc. 
 *               1993-1995 Microsoft Corporation 
 * 
 * ALL RIGHTS RESERVED 
 * 
 * Please refer to OpenGL/readme.txt for additional information 
 * 
 */ 
 
/* 
 *  tea.c 
 *  This program demonstrates two-sided lighting and compares 
 *  it with one-sided lighting.  Three teapots are drawn, with 
 *  a clipping plane to expose the interior of the objects. 
 */ 
#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); 
 
/*  Initialize light source. 
 */ 
void myinit(void) 
{ 
    GLfloat light_ambient[] = { 0.0, 0.0, 0.0, 1.0 }; 
    GLfloat light_diffuse[] = { 1.0, 1.0, 1.0, 1.0 }; 
    GLfloat light_specular[] = { 1.0, 1.0, 1.0, 1.0 }; 
/*  light_position is NOT default value */ 
    GLfloat light_position[] = { 1.0, 1.0, 1.0, 0.0 }; 
 
    glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient); 
    glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse); 
    glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular); 
    glLightfv(GL_LIGHT0, GL_POSITION, light_position); 
     
    glFrontFace (GL_CW); 
    glEnable(GL_LIGHTING); 
    glEnable(GL_LIGHT0); 
    glEnable(GL_AUTO_NORMAL); 
    glEnable(GL_NORMALIZE); 
    glDepthFunc(GL_LESS); 
    glEnable(GL_DEPTH_TEST); 
} 
 
void CALLBACK display(void) 
{ 
    GLdouble eqn[4] = {1.0, 0.0, -1.0, 1.0}; 
    GLfloat two_side_on[] = { GL_TRUE }; 
    GLfloat two_side_off[] = { GL_FALSE }; 
    GLfloat mat_diffuse[] = { 0.8, 0.8, 0.8, 1.0 }; 
    GLfloat back_diffuse[] = { 0.8, 0.2, 0.8, 1.0 }; 
 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
 
    glPushMatrix (); 
    glClipPlane (GL_CLIP_PLANE0, eqn);  /*  slice objects   */ 
    glEnable (GL_CLIP_PLANE0);  
 
    glPushMatrix (); 
    glTranslatef (0.0, 2.0, 0.0); 
    auxSolidTeapot(1.0);    /*  one-sided lighting  */ 
    glPopMatrix (); 
 
    /*  two-sided lighting, but same material   */ 
    glLightModelf (GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE); 
    glMaterialfv (GL_FRONT_AND_BACK, GL_DIFFUSE, mat_diffuse); 
    glPushMatrix (); 
    glTranslatef (0.0, 0.0, 0.0); 
    auxSolidTeapot(1.0); 
    glPopMatrix (); 
 
    /*  two-sided lighting, two different materials */ 
    glMaterialfv (GL_FRONT, GL_DIFFUSE, mat_diffuse); 
    glMaterialfv (GL_BACK, GL_DIFFUSE, back_diffuse); 
    glPushMatrix (); 
    glTranslatef (0.0, -2.0, 0.0); 
    auxSolidTeapot(1.0); 
    glPopMatrix (); 
 
    glLightModelf (GL_LIGHT_MODEL_TWO_SIDE, GL_FALSE); 
    glDisable (GL_CLIP_PLANE0); 
    glPopMatrix (); 
    glFlush(); 
} 
 
void CALLBACK myReshape(GLsizei w, GLsizei h) 
{ 
    if (!h) return; 
    glViewport(0, 0, w, h); 
    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 
    if (w <= h)  
    glOrtho (-4.0, 4.0, -4.0*(GLfloat)h/(GLfloat)w,  
        4.0*(GLfloat)h/(GLfloat)w, -10.0, 10.0); 
    else  
    glOrtho (-4.0*(GLfloat)w/(GLfloat)h,  
        4.0*(GLfloat)w/(GLfloat)h, -4.0, 4.0, -10.0, 10.0); 
    glMatrixMode(GL_MODELVIEW); 
} 
 
/*  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); 
    auxInitPosition (0, 0, 500, 500); 
    auxInitWindow ("Two Sided Lighting"); 
    myinit(); 
    auxReshapeFunc (myReshape); 
    auxMainLoop(display); 
    return(0); 
}