3D Shooters for Quake - Pro Android Games - page 213

Tip Yaw (also known as heading) is the angular movement of the eye in the X axis. Pitch is the
angular movement of the eye in the Y axis.
Note that yaw and pitch are controlled by the mouse_x and mouse_y variables. These are
delta increments in the XY axis sent through JNI by the QuakeView Java class. The center
of the screen represents the origin (0,0). Down or left increments are negative, up or right
increments are positive. The function V_StopPitchDrift stops the drift of the pitch angle
back to the origin whenever the movement stops (by lifting the finger). This is typical
behavior of Quake in the desktop (if you aim with the mouse, as soon as you move it outside
the game view, your aim will drift back to the origin).
Handling Forward and Side Movement
Forward and side movements are handled in a way similar to pitch and yaw. Quake uses
built-in data structures: cmd->sidemove to control side movements and cmd->forwardmove for
forward movement (see Listing 6-13). These variables need to be increased or decreased
by some increment. In this case, the increments are controlled by the variables mouse_side
and mouse_fwd . These two variables will be updated by JNI whenever you drag a finger on
the screen. The companion JNI implementations are described in the previous section,
“Handling Touch.”
Note that both forward and side movements are multiplied by two Quake default values,
m_side and m_forward . These are used to control the range of movement; also keep in mind
that mouse_side and mouse_fwd are delta values in the XY direction where the origin (0,0) is
defined at the point where the finger goes down. The delta values are then calculated by
subtracting the XY coordinates of the pointer and then sent through JNI for consumption.
Listing 6-13. Handling Forward and Side Movement
// these will be updated by JNI
int mouse_side;
int mouse_fwd;
void IN_FwdSideMove (usercmd_t *cmd)
{
cmd->sidemove += m_side.value * mouse_side;
cmd->forwardmove -= m_forward.value * mouse_fwd;
}
void IN_Move (usercmd_t *cmd)
{
IN_FwdSideMove (cmd);
IN_LookMove (cmd)
}