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Menu Support
[Tutorial 3 - User Interaction 2]

Adding the Menu

The skeleton contains source code that builds and maintains a menuing system. This has proven useful for our examples, where different effects are often needed to be chosen by the user. We will add a menu to help us interact with our code.

• Look at the InitializeMenu() function in main.c. After opening the menu, the code adds a single entry that is used to toggle the state of the frames-per-second display.

      static RwBool 
      InitializeMenu(void)
      {    
          static RwChar fpsLabel[] = RWSTRING("FPS_F");
  

          if( MenuOpen(TRUE, &ForegroundColor, &BackgroundColor) )
          {
              MenuAddEntryBool(fpsLabel, &FPSOn, NULL);
  

              return TRUE;
          }
  

          return FALSE;
      }
  

  The near clipping plane is set to 0.1 units by the application. When cubes are moved forward using the new mouse interaction code, you will find that they are clipped against this clipping plane. To control this clipping we will add a console command to adjust the distance of the near clipping plane from the camera. The skeleton code implements a number of useful functions that add support for toggles (Booleans), and integer and real number values. We will add new entries to allow the near and far clip planes to be adjusted. We will use the MenuAddEntryReal() function for this.

• Modify the InitializeMenu() function to add two new menu entries, one each for the near and far clip planes:

      static RwBool 
      InitializeMenu(void)
      {    
          static RwChar fpsLabel[] = RWSTRING("FPS_F");
          static RwChar nearLabel[] = RWSTRING("Near Clip");
          static RwChar farLabel[] = RWSTRING("Far Clip");
  

          if( MenuOpen(TRUE, &ForegroundColor, &BackgroundColor) )
          {
              MenuAddEntryBool(fpsLabel, &FPSOn, NULL);
              MenuAddEntryReal(nearLabel, &NearClip, NULL, 0.1f, 10.0f, 0.1f);
              MenuAddEntryReal( farLabel, & FarClip, NULL, 10.0f, 100.0f, 1.0f);
  

              return TRUE;
          }
  

          return FALSE;
      }
  

• Create the two static variables NearClip and FarClip of type RwReal.

      static RpAtomic *PickedAtomic = NULL;
      static RwBBox PickBox;
      static RwV2d OldPos;
  

      static RwReal NearClip = 0.1f;
      static RwReal FarClip = 30.0f;
  

      RpWorld *World = NULL;
      RwCamera *Camera = NULL;
  

• Next add code to the Render() function to use the user-supplied near and far clip-plane values:

      static void 
      Render(void)
      {
          RwCameraSetNearClipPlane(Camera, NearClip);
          RwCameraSetFarClipPlane(Camera, FarClip);
          RwCameraClear(Camera, &BackgroundColor, rwCAMERACLEARZ|rwCAMERACLEARIMAGE);
  

          if( RwCameraBeginUpdate(Camera) )
  

• Now compile and run your application. Create a cube, and drag it forward and backwards. Change the clip-plane values to check that the clipping works as expected.
  

Next...

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