INT32GP Graphics Programming: Tutorial #17
More Hierarchical Modelling

• A camera is aimed at a wireframe hierarchical object (dancer) with green body and magenta head.
• Move the dancer in and out along the z-axis using the Page Up and Page Down special keys.
• Move the head backwards and forwards, independent of the body, by pressing the h key.
• Toggle between perspective and orthographic projection via the p key. The default is perspective projection.
• Increase fovy (field of view) of the camera via the f key.
• Decrease fovy via the F key.
• When the window is resized, the proportions of objects in the window are preserved and the x and y origins are repositioned so that objects occupy the same region of the new window.

1. Change the code in renderView() so that there are two calls to renderDancer().

   void renderView(){
      glTranslated(t[dancer][x],t[dancer][y],t[dancer][z]);
      renderDancer();
      renderDancer();
   }

2. Observe that this code does not result in two dancers next to each other.
3. What happens when you rotate the head?
4. Change the code in renderView() to push and pop the GL_MODELVIEW matrix.

      glTranslated(t[dancer][x],t[dancer][y],t[dancer][z]);
      glPushMatrix();
      renderDancer();
      glPopMatrix();
      renderDancer();

5. Describe the change. What happens when you press the Page Up and Page Down keys?
6. Move glPushMatrix() so that only the first dancer responds the the Page Up and Page Down keys.
7. Use a translation to place the dancers next to each other.
8. Use translation(s) to move only the second dancer along the x-axis in response to the x key. When dancer 2 reaches the xRight clipping plane reverse direction. Similarly, when dancer 2 reaches the xLeft clipping plane automatically reverse direction.
9. Use orthographic projection to check that this is working.
10. Use translation and scaling to place a third dancer, half the size of the other two, next to the first.

1. Edit void initialiseGL(), adding the following.

      glLightModelfv(GL_LIGHT_MODEL_AMBIENT,ambient);
      glEnable(GL_LIGHTING);
      glEnable(GL_COLOR_MATERIAL);

2. Set up ambient light globally.

   /*
   ** manage lights
   */
   GLfloat ambient[]={0.5,0.5,0.5,1.0};

3. Toggle between a filled and wire rendering tool - hints follow.

   GLUquadricObj * renderTool;
   int wire=TRUE;
   
   if(wire)
         gluQuadricDrawStyle(renderTool,GLU_LINE);
   else
         gluQuadricDrawStyle(renderTool,GLU_FILL);

• Both heads rotate.
• Dancer 2 moves back and forth along the x-axis.
• Dancer 1 moves forward and back along the z-axis, reversing direction when it reaches the zNear or the zFar clipping plane.