OpenGL学习入门： 光照示例

This program demonstrates when to issue lighting and transformation commands to render a model with a light which is moved by a modeling transformation (rotate or translate). The light position is reset after the modeling transformation is called. The eye position does not change. A sphere is drawn using a grey material characteristic. A single light source illuminates the object. Interaction: pressing the left or middle mouse button alters the modeling transformation (x rotation) by 30 degrees. The scene is then redrawn with the light in a new position.

/* Copyright (c) Mark J. Kilgard, 1994. *//* This program is freely distributable without licensing fees    and is provided without guarantee or warrantee expressed or    implied. This program is -not- in the public domain. *//** * (c) Copyright 1993, Silicon Graphics, Inc. * ALL RIGHTS RESERVED  * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS" * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE, * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT, * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION, * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE. *  * US Government Users Restricted Rights  * Use, duplication, or disclosure by the Government is subject to * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph * (c)(1)(ii) of the Rights in Technical Data and Computer Software * clause at DFARS 252.227-7013 and/or in similar or successor * clauses in the FAR or the DOD or NASA FAR Supplement. * Unpublished-- rights reserved under the copyright laws of the * United States.  Contractor/manufacturer is Silicon Graphics, * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311. * * OpenGL(TM) is a trademark of Silicon Graphics, Inc. *//** *  movelight.c *  This program demonstrates when to issue lighting and  *  transformation commands to render a model with a light  *  which is moved by a modeling transformation (rotate or  *  translate).  The light position is reset after the modeling  *  transformation is called.  The eye position does not change. * *  A sphere is drawn using a grey material characteristic.  *  A single light source illuminates the object. * *  Interaction:  pressing the left or middle mouse button *  alters the modeling transformation (x rotation) by 30 degrees.   *  The scene is then redrawn with the light in a new position. */#include <stdlib.h>#include <stdarg.h>#include <stdio.h>#include <GL/glut.h>#define TORUS 0#define TEAPOT 1#define DOD 2#define TET 3#define ISO 4#define QUIT 5static int spin = 0;static int obj = TORUS;static int begin;voidoutput(GLfloat x, GLfloat y, char *format,...){  va_list args;  char buffer[200], *p;  va_start(args, format);  vsprintf(buffer, format, args);  va_end(args);  glPushMatrix();  glTranslatef(x, y, 0);  for (p = buffer; *p; p++)    glutStrokeCharacter(GLUT_STROKE_ROMAN, *p);  glPopMatrix();}voidmenu_select(int item){  if (item == QUIT)    exit(0);  obj = item;  glutPostRedisplay();}/* ARGSUSED2 */voidmovelight(int button, int state, int x, int y){  if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {    begin = x;  }}/* ARGSUSED1 */voidmotion(int x, int y){  spin = (spin + (x - begin)) % 360;  begin = x;  glutPostRedisplay();}voidmyinit(void){  glEnable(GL_LIGHTING);  glEnable(GL_LIGHT0);  glDepthFunc(GL_LESS);  glEnable(GL_DEPTH_TEST);}/*  Here is where the light position is reset after the modeling *  transformation (glRotated) is called.  This places the  *  light at a new position in world coordinates.  The cube *  represents the position of the light. */voiddisplay(void){  GLfloat position[] =  {0.0, 0.0, 1.5, 1.0};  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  glMatrixMode(GL_MODELVIEW);  glPushMatrix();  glTranslatef(0.0, 0.0, -5.0);  glPushMatrix();  glRotated((GLdouble) spin, 0.0, 1.0, 0.0);  glRotated(0.0, 1.0, 0.0, 0.0);  glLightfv(GL_LIGHT0, GL_POSITION, position);  glTranslated(0.0, 0.0, 1.5);  glDisable(GL_LIGHTING);  glColor3f(0.0, 1.0, 1.0);  glutWireCube(0.1);  glEnable(GL_LIGHTING);  glPopMatrix();  switch (obj) {  case TORUS:    glutSolidTorus(0.275, 0.85, 20, 20);    break;  case TEAPOT:    glutSolidTeapot(1.0);    break;  case DOD:    glPushMatrix();    glScalef(.5, .5, .5);    glutSolidDodecahedron();    glPopMatrix();    break;  case TET:    glutSolidTetrahedron();    break;  case ISO:    glutSolidIcosahedron();    break;  }  glPopMatrix();  glPushAttrib(GL_ENABLE_BIT);  glDisable(GL_DEPTH_TEST);  glDisable(GL_LIGHTING);  glMatrixMode(GL_PROJECTION);  glPushMatrix();  glLoadIdentity();  gluOrtho2D(0, 3000, 0, 3000);  glMatrixMode(GL_MODELVIEW);  glPushMatrix();  glLoadIdentity();  output(80, 2800, "Welcome to movelight.");  output(80, 2650, "Right mouse button for menu.");  output(80, 400, "Hold down the left mouse button");  output(80, 250, "and move the mouse horizontally");  output(80, 100, "to change the light position.");  glPopMatrix();  glMatrixMode(GL_PROJECTION);  glPopMatrix();  glPopAttrib();  glutSwapBuffers();}voidmyReshape(int w, int h){  glViewport(0, 0, w, h);  glMatrixMode(GL_PROJECTION);  glLoadIdentity();  gluPerspective(40.0, (GLfloat) w / (GLfloat) h, 1.0, 20.0);  glMatrixMode(GL_MODELVIEW);}voidtmotion(int x, int y){  printf("Tablet motion x = %d, y = %d\n", x, y);}voidtbutton(int b, int s, int x, int y){  printf("b = %d, s = %d, x = %d, y = %d\n", b, s, x, y);}voidsmotion(int x, int y, int z){  fprintf(stderr, "Spaceball motion %d %d %d\n", x, y, z);}voidrmotion(int x, int y, int z){  fprintf(stderr, "Spaceball rotate %d %d %d\n", x, y, z);}voidsbutton(int button, int state){  fprintf(stderr, "Spaceball button %d is %s\n",    button, state == GLUT_UP ? "up" : "down");}voiddials(int dial, int value){  fprintf(stderr, "Dial %d is %d\n", dial, value);  spin = value % 360;  glutPostRedisplay();}voidbuttons(int button, int state){  fprintf(stderr, "Button %d is %s\n", button,    state == GLUT_UP ? "up" : "down");}/*  Main Loop *  Open window with initial window size, title bar,  *  RGBA display mode, and handle input events. */intmain(int argc, char **argv){  glutInit(&argc, argv);  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);  glutInitWindowSize(500, 500);  glutCreateWindow(argv[0]);  myinit();  glutMouseFunc(movelight);  glutMotionFunc(motion);  glutReshapeFunc(myReshape);  glutDisplayFunc(display);  glutTabletMotionFunc(tmotion);  glutTabletButtonFunc(tbutton);  glutSpaceballMotionFunc(smotion);  glutSpaceballRotateFunc(rmotion);  glutSpaceballButtonFunc(sbutton);  glutDialsFunc(dials);  glutButtonBoxFunc(buttons);  glutCreateMenu(menu_select);  glutAddMenuEntry("Torus", TORUS);  glutAddMenuEntry("Teapot", TEAPOT);  glutAddMenuEntry("Dodecahedron", DOD);  glutAddMenuEntry("Tetrahedron", TET);  glutAddMenuEntry("Icosahedron", ISO);  glutAddMenuEntry("Quit", QUIT);  glutAttachMenu(GLUT_RIGHT_BUTTON);  glutMainLoop();  return 0;             /* ANSI C requires main to return int. */}