Cube Rotation - OpenGL

Question

i heed help with openGL and rotations. This is My code:

#include <math.h>
#include <GL/glut.h>


float transZ=50;      
float rotateA=0;         

float rotateAspeed=0.0;

void cube (float dimX, float dimY, float dimZ)
{
   glMatrixMode(GL_MODELVIEW);
   glPushMatrix();


      glTranslatef(0,dimY/2,0);

      glScalef(dimX/2, dimY/2, dimZ/2);


  glBegin(GL_QUADS);        
    glColor3f(0.0, 1.0, 0.0);    // Color Green - TOP

    glVertex3f(1.0, 1.0, 1.0); // TOP-RIGHT-NEAR
    glVertex3f(-1.0, 1.0, 1.0); // TOP-LEFT-NEAR
    glVertex3f(-1.0, 1.0, -1.0); //TOP-LEFT-FAR
    glVertex3f(1.0, 1.0, -1.0); // TOP-RIGHT-FAR

    glColor3f(1.0, 0.0, 0.0); // Color RED - Bottom

    glVertex3f(1.0, -1.0, 1.0); //BOTTOM-RIGHT-NEAR
    glVertex3f(-1.0, -1.0, 1.0); //BOTTOM-LEFT-NEAR
    glVertex3f(-1.0, -1.0, -1.0); //BOTTOM-LEFT-FAR
    glVertex3f(1.0, -1.0, -1.0); //BOTTOM-RIGHT-FAR

    glColor3f(1.0, 1.0, 0.0); // Color Yellow - Back

    glVertex3f(1.0, 1.0, -1.0); //TOP-RIGHT-FAR
    glVertex3f(-1.0, 1.0, -1.0); //TOP-LEFT-FAR
    glVertex3f(-1.0, -1.0, -1.0); //BOTTOM-LEFT-FAR
    glVertex3f(1.0, -1.0, -1.0); //BOTTOM-RIGHT-FAR

    glColor3f(0.0, 0.0, 1.0); //Color Blue - RIGHT

    glVertex3f(1.0, 1.0, 1.0); //TOP-FRONT-NEAR
    glVertex3f(1.0, 1.0, -1.0); //TOP-BACK-FAR
    glVertex3f(1.0, -1.0, -1.0); //BOTTOM-BACK-FAR
    glVertex3f(1.0, -1.0, 1.0); //BOTTOM-FRONT-NEAR

    glColor3f(1.0, 0.5, 0.0); //Color Orange - Left

    glVertex3f(-1.0, 1.0, 1.0); //TOP-FRONT-NEAR
    glVertex3f(-1.0, 1.0, -1.0); //TOP-BACK-FAR
    glVertex3f(-1.0, -1.0, -1.0);//BOTTOM-BACK-FAR
    glVertex3f(-1.0, -1.0, 1.0); //BOTTOM-FRONT-NEAR




  glEnd();


   glPopMatrix();
}


void display(void)
{


   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );


   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();


   gluLookAt(transZ*cos(rotateA),10,transZ*sin(rotateA), 0,10,0, 0,1,0);


   cube(30,30,30);


   glFlush();            

   glutSwapBuffers();
}

void init (void)
{
   glClearColor(1.0, 1.0, 1.0, 1.0);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();

   glFrustum(-1, 1, -1, 1, 1, 1000);


   glEnable(GL_DEPTH_TEST); 
}


void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 27:                
         exit(0);
         break;
      case 'S':
         transZ+=1.0f;
         glutPostRedisplay();  
         break;
      case 'W':
         transZ-=1.0f;
         if (transZ<0) transZ=0;
         glutPostRedisplay();  
         break;
      case 's':
         transZ+=0.5f;
         glutPostRedisplay();  
         break;
      case 'w':
         transZ-=0.5f;
         if (transZ<0) transZ=0;
         glutPostRedisplay(); 
         break;
      case 'A':
         rotateAspeed+=0.001f;
         glutPostRedisplay();  
         break;
      case 'a':
         rotateAspeed+=0.001f;
         glutPostRedisplay();  
         break;
      case 'D':
         rotateAspeed-=0.001f;
         glutPostRedisplay();  
         break;
      case 'd':
         rotateAspeed-=0.001f;
         glutPostRedisplay();  
         break;

   }
}

void idle(void)
{
  rotateA=rotateA + rotateAspeed;
  glutPostRedisplay();    
}



int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (500, 500);
   glutInitWindowPosition (100, 100);
   glutCreateWindow ("Cube");
   init ();

   glutDisplayFunc(display);
   glutIdleFunc(idle); 

   glutKeyboardFunc(keyboard); 
   glutMainLoop();
   return 0;
}

When i press A or D the cube is rotated horizontally but i need to make, when i press, for example J the cube to start rotating vertically. Any help on how to do that?

Answer 1

You need to look at glRotate and how transformations are done in openGL. Then parameterize the rotation by three angles, called Euler angles, or use quaternions, or some other suitable rotation representation. From this the transformations will rotate the cube properly, it might look like this:

glPushMatrix()
glRotatef(alpha, 1, 0, 0); //rotate alpha around the x axis
glRotatef(beta, 0, 1, 0); //rotate beta around the y axis
glRotatef(gamma, 0, 0, 1); //rotate gamma around the z axis

//dram my cube
glPopMatrix();