---

Moving Atomics in Depth
[Tutorial 3 - User Interaction 2]

We will modify the mouse handling code to drag atomics in depth when the control key is held down. This will require an extra member for the MouseMoveOperation enumerated type, code to test for the control key being held down, and the code to actually move the selected atomic in depth.

• Add new members to MouseMoveOperation called MMPickAndZTranslateObject and MMZTranslateObject:

      #ifndef UTILS
      #define UTILS
      typedef enum {
          MMNoOperation,
          MMPickAndTranslateObject,
          MMPickAndRotateObject,
          MMPickAndZTranslateObject,
          MMTranslateObject,
          MMRotateObject,
          MMZTranslateObject,
  

          MOUSEMOVEOPERATIONFORCEENUMSIZEINT = RWFORCEENUMSIZEINT
      } MouseMoveOperation;
  

• In the HandleLeftButtonDown() function in win/events.c, test to see if the mouseStatus->control field is set, and if so enter the MMPickAndZTranslateObject state. (You might want to add this after the test for the shift key, but before the default MMPickAndTranslateObject action.)

      static RsEventStatus
      HandleLeftButtonDown(RsMouseStatus *mouseStatus)
      {
          /* Left mouse button down event handling... */
          if (mouseStatus->shift)
          {
              MouseMoveAction = MMPickAndRotateObject;
          }
  

          else if (mouseStatus->control)
          {
              MouseMoveAction = MMPickAndZTranslateObject;
          }
  

          else
          {
              MouseMoveAction = MMPickAndTranslateObject;
          }
  

          return rsEVENTPROCESSED;
      }
  

• Next, simplify the switch statement in the Idle() function. All of the picking code is identical, except for the mode to enter after the pick is performed. You will write the PickAtomic() and ZTranslateAtomic() functions next.

          switch(MouseMoveAction)
          {
          case MMPickAndTranslateObject :
              PickAtomic(MMTranslateObject);
              break;
          case MMTranslateObject :
              TranslateAtomic();
              break;
          case MMPickAndRotateObject :
              PickAtomic(MMRotateObject);
              break;
          case MMRotateObject :
              RotateAtomic();
              break;
          case MMPickAndZTranslateObject :
              PickAtomic(MMZTranslateObject);
              break;
          case MMZTranslateObject :
              ZTranslateAtomic();
              break;
          default:
              PickedAtomic = NULL;
              break;
          }
  

• Finally, add the code for the PickAtomic() and ZTranslateAtomic() functions:

      static void
      PickAtomic(MouseMoveOperation nextOp)
      {
          PickedAtomic = RwCameraPickAtomicOnPixel(Camera, &MousePos);
          if (PickedAtomic)
          {
              AtomicGetBBox(PickedAtomic, &PickBox);
              OldPos = MousePos;
              MouseMoveAction = nextOp;
          }
  

          else
          {
              MouseMoveAction = MMNoOperation;
          }
  

      }
  

      static void
      ZTranslateAtomic(void)
      {
          RwReal dy;
          RwFrame *f;
          RwV3d at;
          f = RwCameraGetFrame(Camera);
          dy = OldPos.y - MousePos.y;
          at = *RwMatrixGetAt(RwFrameGetMatrix(f));
          RwV3dScale(&at, &at, dy*0.01f);
          f = RpAtomicGetFrame(PickedAtomic);
          RwFrameTranslate(f, &at, rwCOMBINEPOSTCONCAT);
          OldPos = MousePos;
      }
  

• Compile and run your code. You should find that you can now move the selected atomic backwards and forwards as the mouse is moved up and down when the control key and left mouse button are held down.
  

Next...

---