《高效学习OpenGL》 之 控制光源的位置和方向

1.如何使光源保持静止

在使用完视图和模型变换之前设置光源的位置，init()的后面， display()之前

2.独立的移动光源

在模型变换之后设置光源位置

#include 
#include 

static int spin = 0;

void init(void) 
{
   glClearColor (0.0, 0.0, 0.0, 0.0);
   glShadeModel (GL_SMOOTH);
   glEnable(GL_LIGHTING);
   glEnable(GL_LIGHT0);
   glEnable(GL_DEPTH_TEST);
}

void display(void)
{
   GLfloat position[] = { 0.0, 0.0, 1.5, 1.0 };

   glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glPushMatrix ();//用于隔离视图变换和模型变换
   gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

   glPushMatrix ();//用于隔离视图变换和模型变换
   glRotated ((GLdouble) spin, 1.0, 0.0, 0.0);//旋转光源
   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 ();//局部坐标系归位
   glutSolidTorus (0.25, 0.85, 8, 15);
   glPopMatrix ();
   glFlush ();
}

void reshape (int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity();
   gluPerspective(40.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

void mouse(int button, int state, int x, int y)
{
   switch (button) {
      case GLUT_LEFT_BUTTON:
         if (state == GLUT_DOWN) {
            spin = (spin + 30) % 360;
            glutPostRedisplay();
         }
         break;
      default:
         break;
   }
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 27:
         exit(0);
         break;
   }
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (500, 500); 
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   init ();
   glutDisplayFunc(display); 
   glutReshapeFunc(reshape);
   glutMouseFunc(mouse);
   glutKeyboardFunc(keyboard);
   glutMainLoop();
   return 0;
}

3.光源和观测点一起移动

void display(void)
{
   GLfloat position[] = { 0.0, 0.0, 1.5, 1.0 };

   glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glPushMatrix ();
   gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

   //glPushMatrix ();
   glRotated ((GLdouble) spin, 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 ();
   glTranslated (0.0, 0.0, 1.5);//增加的代码

   glutSolidTorus (0.275, 0.85, 8, 15);
   glPopMatrix ();
   glFlush ();
}