Game Development Reference
In-Depth Information
//lookradians the same as carRadians for middle
lookAheadPoints[1].x=player.nextX+Math.cos(carRadians)*player.radius;
lookAheadPoints[1].y = player.nextY + Math.sin(carRadians) * player.radius;
lookRadians = ((player.nextRotation+45) / 360) * (2.0 * Math.PI);
lookAheadPoints[2].x = (player.nextX + Math.cos(lookRadians) * player.radius);
lookAheadPoints[2].y = (player.nextY + Math.sin(lookRadians) * player.radius);
}
}
This is the detailed description of the main points of the
update
function:
1.
The
player.move
Boolean is set to
true
. When we do collision detection, we will set this
to
false
if any one of the three
LookAheadPoint
references returns true for a
WALL
hit.
2.
Next, we set the turn speed for the player. This relates directly to the actual
velocity
of the car. The maximum turn speed is .6 and minimum is .3, and we can set these
speeds in a simple linear relation to the velocity. We simply divide the current velocity
by 10 and add it to the
player.minTurnSpeed
. Then we check to make sure it isn't over
our
player.maxTurnSpeed
.
3.
Exactly as in the previous section in this chapter on moving the car about the world (see
“Adding basic car physics to our game”),we calculate the new
dx
and
dy
values using the
player.nextRotation
value and the current velocity of the player. We update the
player.worldNextX
and
player.worldNextY
with the
dx
and
dy
values. The
camera.nextX
and
camera.nexty
values are based on this new world position for the player.
4.
Next, we set the
nextX
of the camera in a similar fashion to how we described
orienting it in the discussion in iteration 2. If the
camera.nextX
or
camera.nextY
is off
the top, bottom, right, or left of the screen, we orient the associated axis back to 0 and
move the player instead.
5.
The final thing we do is set the three look ahead points to the front, middle, left, and
right of the car if it is going forward (velocity greater than 0) and to the rear of the car if
the velocity is less than 0.
We find these mathematically by calculating the radians for a 45-degree angle from the center of the
car in each of the positive and negative directions and multiply this number by the radius we
calculated earlier (16). The middle
LookAheadPoint
simply uses the radians for the current rotation.
See Figure 10-10 for an example.
Figure 10-10.
Calculated LookAheadPoint instances
