[OpenGL]课后案例09：立方体旋转程序

//A.9  立方体旋转程序
/* Rotating cube with color interpolation */
/* Demonstration of use of homogeneous coordinate 
transformations and simple data structure for representing
cube from Chapter 4 */
/* Colors are assigned to the vertices */
/* cube is centered at orign*/
#include 
#include 
GLfloat vertices[][3] = {{-1.0,-1.0,-1.0},{1.0,-1.0,-1.0},
{1.0,1.0,-1.0}, {-1.0,1.0,-1.0}, {-1.0,-1.0,1.0},  
{1.0,-1.0,1.0}, {1.0,1.0,1.0}, {-1.0,1.0,1.0}};
GLfloat colors[][3] = {{0.0,0.0,0.0},{1.0,0.0,0.0},
{1.0,1.0,0.0}, {0.0,1.0,0.0}, {0.0,0.0,1.0}, 
{1.0,0.0,1.0}, {1.0,1.0,1.0}, {0.0,1.0,1.0}};
void polygon(int a, int b, int c, int d)
{
	/* draw a polygon via list of vertices */
	glBegin(GL_POLYGON);
	glColor3fv(colors[a]);
	glVertex3fv(vertices[a]);
	glColor3fv(colors[b]);
	glVertex3fv(vertices[b]);
	glColor3fv(colors[c]);
	glVertex3fv(vertices[c]);
	glColor3fv(colors[d]);
	glVertex3fv(vertices[d]);
	glEnd();
}
void colorcube(void)
{
	/* map vertices to faces */
	polygon(0,3,2,1);
	polygon(2,3,7,6);
	polygon(0,4,7,3);
	polygon(1,2,6,5);
	polygon(4,5,6,7);
	polygon(0,1,5,4);
}
static GLfloat theta[] = {0.0,0.0,0.0};
static GLint axis = 2; 
void display(void)
{
	/* display callback, clear frame buffer and z buffer,
	rotate cube and draw, swap buffers */
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();
	glRotatef(theta[0], 1.0, 0.0, 0.0);
	glRotatef(theta[1], 0.0, 1.0, 0.0);
	glRotatef(theta[2], 0.0, 0.0, 1.0);
	colorcube();
	glFlush();
	glutSwapBuffers();
}
void spinCube()
{
	/* Idle callback, spin cube 2 degrees about selected axis */
	theta[axis] += 2.0;
	if( theta[axis] > 360.0 ) theta[axis] -= 360.0;
	/* display(); */
	glutPostRedisplay();
}
void mouse(int btn, int state, int x, int y)
{
	/* mouse callback, selects an axis about which to rotate */
	if(btn==GLUT_LEFT_BUTTON && state == GLUT_DOWN) axis = 0;
	if(btn==GLUT_MIDDLE_BUTTON && state == GLUT_DOWN) axis = 1;
	if(btn==GLUT_RIGHT_BUTTON && state == GLUT_DOWN) axis = 2;
}
void myReshape(int w, int h) 
{
	glViewport(0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	if (w <= h)
		glOrtho(-2.0, 2.0, -2.0 * (GLfloat) h / (GLfloat) w,
		2.0 * (GLfloat) h / (GLfloat) w, -10.0, 10.0);
	else
		glOrtho(-2.0 * (GLfloat) w / (GLfloat) h,
		2.0 * (GLfloat) w / (GLfloat) h, -2.0, 2.0, -10.0, 10.0);
	glMatrixMode(GL_MODELVIEW);
}
void main(int argc, char **argv)
{
	glutInit(&argc, argv);
	/* need both double buffering and z buffer */
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowSize(500, 500);
	glutCreateWindow("colorcube");
	glutReshapeFunc(myReshape);
	glutDisplayFunc(display);
	glutIdleFunc(spinCube);
	glutMouseFunc(mouse);
	glEnable(GL_DEPTH_TEST); /* Enable hidden-surface removal */
	glutMainLoop();
}