Game Engine Architecture

360 8. Human Interface Devices (HID)

++m_iButton; // advance to next button

// Is the sequence complete?

if (m_iButton == m_buttonCount)

{

BroadcastEvent(m_eventId);

m_iButton = 0; // reset

}

}

else

{

// Sorry, not fast enough.

m_iButton = 0; // reset

}

}

}

}

};

Thumb Stick Rotation

As an example of a more-complex gesture, let’s see how we might detect when

the player is rotating the left thumb stick in a clockwise circle. We can detect

this quite easily by dividing the two-dimensional range of possible stick po-

sitions into quadrants, as shown in Figure 8.10. In a clockwise rotation, the

stick passes through the upper-left quadrant, then the upper-right, then the

lower-right, and fi nally the lower-left. We can treat each of these cases like a

butt on press and detect a full rotation with a slightly modifi ed version of the

sequence detection code shown above. We’ll leave this one as an exercise for

the reader. Try it!

x

y

UL UR

LL LR

Figure 8.10. Detecting circular rotations of the stick by dividing the 2D range of stick inputs

into quadrants.