INT32GP Graphics Programming: Tutorial #16
GLU Quadrics and Hierarchical Modelling

• Toggle between perspective and orthographic projection via the p key.
• Increase fovy (field of view) of the camera via the f key.
• Decrease fovy via the F key.
• When the window is resized, make sure the proportions of objects in the window are preserved and reposition the x and y origins so that objects occupy the same region of the new window.

1. Globally declare a quadrics object.

   /* manage model */
   GLUquadricObj * wireTool;

2. Create and delete wireTool in display().

   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   wireTool=gluNewQuadric();
   gluQuadricDrawStyle(wireTool,GLU_LINE);
   renderView();
   glFlush();
   gluDeleteQuadric(wireTool);

3. Render the body. It would be better programming style to use variable names for the gluCylinder function parameters.

   void renderDancer(){
      glColor3fv(colour[green]);
      gluCylinder(wireTool,1.0,0.25,1.7,9,2);
   }
   void renderView(){
      renderDancer();
   }

4. Observe how the smaller top radius is facing towards the camera down the positive z-axis. The larger base radius is centred around the origin.
5. Try toggling perspective projection on and off and changing the field of view.
6. Render the head in magenta (radius 0.45). It will be rendered around the origin.

   glColor3fv(colour[magenta]);
   gluSphere(wireTool,0.45,15,15);

7. Use a translation to move the head to the top of the body.
• Since we will be translating a number of objects, set up a data structure to handle transforms. For the time being it only handles the head which must move along the z-axis.

  /* manage model transforms */
  enum {head};
  GLdouble t[][3]={
     {0,0,1.925}
  };

• Place the following line in the appropriate position in renderDancer().

     glTranslated(t[head][x],t[head][y],t[head][z]);

8. Stand the dancer upright. Which axis do we have to rotate around?
• Later, we will rotate the head and translate the dancer. So make the following alterations to your global transform data structures.

  enum {dancer,head};
  GLdouble t[][3]={
     {0,0,0},{0,0,1.925}
  };
  GLdouble ra[]={
     -90,0
  };
  GLdouble r[][3]={
     {1,0,0},{0,0,1}
  };
  

• If you place the following code in the appropriate position, the dancer will be upright in front of the camera.

  glRotated(ra[dancer],r[dancer][x],r[dancer][y],r[dancer][z]);

9. Use the special function arrow and page up and down keys to translate the dancer along the x, y, and z-axes.
• Place the following code in the appropriate position. I would place it in renderView() before the code to renderDancer().
glTranslated(t[dancer][x],t[dancer][y],t[dancer][z]);
• Register a glutSpecialFunc function with GLUT.
• The following code will move the dancer backwards and forwards along the z-axis. Add code to move along the other two axes.

  void specialKeys(int key,int xMouse,int yMouse){
     int i;
     switch(key){
        case GLUT_KEY_PAGE_UP  : t[dancer][z]+= 0.1; break;
        case GLUT_KEY_PAGE_DOWN: t[dancer][z]+=-0.1; break;
     }
     glutPostRedisplay();
  }

10. Rotate the dancer around the y-axis in response to the y key.
11. Rotate the head independent of the body. You may need to push and pop a matrix for this to work.