Rotation 회전

It describes how to rotate objects.

OpenGL에서 오브젝트 회전 하기.

#include <gl/glut.h>
 
GLfloat angle = 0.0f;
 
void MyDisplay();
void MyTimer(int value);
 
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutCreateWindow("OpenGL Rotation");
 
    glutDisplayFunc(MyDisplay);
    glutTimerFunc(20, MyTimer, 1);
 
    glutMainLoop();
 
    return 0;
}
 
void MyDisplay()
{
    glClear(GL_COLOR_BUFFER_BIT);
    
    // 1st teapot, right, CCW
    glPushMatrix();
    glRotatef(45.0f, 1.0f, 0.0f, 0.0f);    // 45 degrees rotation around X-Axis to see the direction of the rotation.
    glTranslatef(0.5f, 0.0f, 0.0f);        // Changing the order of calling this Translate()..
    glRotatef(angle, 0.0f, 1.0f, 0.0f);    // and this Rotate() will affect how it spins. (rotation and revolution)
    glutWireTeapot(0.3);
    glPopMatrix();
    
    // 2nd teapot, left, CW
    glPushMatrix();
    // glPushMatrix pushes the current matrix stack down by one, duplicating the current matrix. That is, after a
    // glPushMatrix call, the matrix on top of the stack is identical to the one below it.
    glRotatef(45.0f, 1.0f, 0.0f, 0.0f);
    glTranslatef(-0.5f, 0.0f, 0.0f);
    glRotatef(-angle, 0.0f, 1.0f, 0.0f);
    glutWireTeapot(0.3);
    glPopMatrix();
    //glPopMatrix pops the current matrix stack, replacing the current matrix with the one below it on the stack.
 
    glutSwapBuffers();
}
 
void MyTimer(int value)
{
    angle += 1.0f;
    if (angle >= 360.0f) {
        angle = 0.0f;
    }
 
    glutPostRedisplay();
    glutTimerFunc(20, MyTimer, 1);
}

Run the program and see the directions of each rotation.