Rotating object around itself in OpenGL

Question

i'm having trouble rotating a room around itself. its center is at (5,5,0) so i thought if i translated the room and the objects in the room with glTranslatef(5,5,5) then glRotatef(rotateroom,0,0,1) and then draw the items and use glTranslate(-5,-5,0) it would rotate the room and everything in it around 5,5,0 but it seems to still be rotating around (0,0,0) and i'm not really sure what I'm doing wrong. Thanks for the help in advance.

void drawside(){
    int i,j;
    /*for (j = 0; j <= 8; j++) {
       glBegin(GL_LINE_STRIP);
       for (i = 0; i <= 30; i++)
          glEvalCoord2f((GLfloat)i/30.0, (GLfloat)j/8.0);
       glEnd();
       glBegin(GL_LINE_STRIP);
       for (i = 0; i <= 30; i++)
          glEvalCoord2f((GLfloat)j/8.0, (GLfloat)i/30.0);
       glEnd();
    }*/
    glEvalMesh2(GL_FILL, 0, 20, 0, 20);
}
void drawRoom(){
    //floor
    glBegin(GL_POLYGON);
    glColor3f(1,1,1);
    glNormal3f(0,0,0);
    glVertex3f(0,0,0);
    glNormal3f(0,10,0);
    glVertex3f(0,10,0);
    glNormal3f(10,10,0);
    glVertex3f(10,10,0);
    glNormal3f(10,0,0);
    glVertex3f(10,0,0);
    glEnd(
    );
    //wall
    glBegin(GL_POLYGON);
    glColor3f(0,0,1);
    glNormal3f(0,10,0);
    glVertex3f(0,10,0);
    glNormal3f(0,10,10);
    glVertex3f(0,10,10);
    glNormal3f(10,10,10);
    glVertex3f(10,10,10);
    glNormal3f(10,10,0);
    glVertex3f(10,10,0);
    glEnd();
    //wall2
    glBegin(GL_POLYGON);
    glColor3f(0,1,0);
    glNormal3f(10,10,0);
    glVertex3f(10,10,0);
    glNormal3f(10,10,0);
    glVertex3f(10,10,10);
    glNormal3f(10,0,10);
    glVertex3f(10,0,10);
    glNormal3f(10,0,0);
    glVertex3f(10,0,0);
    glEnd();
}
void drawObjects(){
    glColor3f(1,0,1);
    glTranslatef(2,2,0);
    if(conefill == 1)
        glShadeModel(GL_FLAT);
    else
        glShadeModel(GL_SMOOTH);
    glutSolidCone(cone,5,10,2);
    glTranslatef(5,5,0);
    glColor3f(1,0,0);
    if(spherefill == 1)
        glShadeModel(GL_FLAT);
    else 
        glShadeModel(GL_SMOOTH);
    glutSolidSphere(sphere,20,20);

}

void display(){
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(viewx,viewy, viewz,viewx +lx, 5, viewz + ly,0.0f, 0.0f,  1.0f);
    //gluLookAt(viewx,viewy,viewz,headup,headright,5,0,0,1);
    glClear(GL_COLOR_BUFFER_BIT);
    GLfloat light_position[] = {-1.0,5.0,5.0,0.0};
    //GLfloat light_direction[] = {-5,-5,-5};
    //GLfloat amb[] = {0,0,0,1};
    glLightfv(GL_LIGHT0, GL_POSITION, light_position);
    //glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION,light_direction);
    //glLightfv(GL_LIGHT0, GL_AMBIENT,amb);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPushMatrix();
    glTranslatef(5,5,0);
    glRotatef(rotateroom,0,0,1);
    glPushMatrix(); 
    drawRoom();
    glPopMatrix();
    glColor3f(0.0, 0.0, 1.0);
    glPushMatrix();
    glTranslatef(6,3,1);
    glPushMatrix ();
    drawside();
    glPopMatrix();
    glPushMatrix();
    //glTranslatef(5,0,0);
    glRotatef(90,1,0,0);
    //glTranslatef(-5,0,0);
    glTranslatef(0,.5,.5);
    drawside();
    glPopMatrix();
    glPushMatrix();
    //glTranslatef(5,0,0);
    glRotatef(180,1,0,0);
    //glTranslatef(-5,0,0);
    glTranslatef(0,1,0);
    drawside();
    glPopMatrix();
    glPushMatrix();
    glRotatef(90,0,0,1);
    glTranslatef(-.5,.5,0);
    drawside();
    glPopMatrix();
    glPushMatrix();
    glRotatef(270,0,0,1);
    glTranslatef(.5,.5,0);
    drawside();
    glPopMatrix();
    glPopMatrix();
    drawObjects();
    glTranslatef(-5,-5,0);
    glPopMatrix();
    glutSwapBuffers();
    glFlush();
}

Please edit down your code so it only shows the relevant parts, i.e. the room drawing code. — Xymostech

Luca Luca · Accepted Answer · 2012-11-25T19:13:11

You only need to invert the order of the istruction:

glRotatef(rotateroom,0,0,1);
glTranslatef(5,5,0);

Whenever you trasform a point you must invert the sequence of trasformation you want to apply. This dipend on the way the transformation matrix are multiplicated.

Rotating object around itself in OpenGL

1 Answers