World Building - jMonkeyEngine 3.0 - page 178

3. Then, create a method called modifyTerrain that takes a Boolean called
pickupCube as the input.
4. To control what is picked up or aimed at, use a pattern that we have established in
the Firing in FPS recipe of Chapter 2 , Cameras and Game Controls . Use a ray
that originates from the camera and moves toward the camera's direction.
5. Now, collide it with the worldnode class of cubeWorld . If it collides with
something and the distance is lower than two (or some other arbitrary number)
and pickupCube is true, we will pick up a cube. Get the worldTransla-
tion vector of the geometry that the ray has collided with. Then, call a method
called changeTerrain in cubeWorld . We'll create the method in a short
while. Now, supply it with the coordinates of the geometry it collides with and the
currently empty takenCube field as follows:
if(coll != null && coll.getDistance() < 2f &&
pickupCube){
Vector3f geomCoords =
coll.getGeometry().getWorldTranslation();
takenCube = cubeWorld.changeTerrain(geomCoords,
takenCube);
}
6. If instead, there is no collision or the collision is too far away, and at the same
time pickupCube is false and takenCube is not null, try to place
takenCube in the world. Since we don't have a collision point, move some way
along the direction of the camera and round it off to the nearest integer. Then, call
cubeWorld.changeTerrain again with the coordinates along with
takenCube , as follows:
Vector3f geomCoords =
cam.getLocation().add(cam.getDirection().mult(2f));
geomCoords.set(Math.round(geomCoords.x),
Math.round(geomCoords.y), Math.round(geomCoords.z));
takenCube = cubeWorld.changeTerrain(geomCoords,
takenCube);
7. In the onAction method, add the logic for the corresponding key press and call
modifyTerrain , supplying either true if we're picking up or false if we're
instead trying to place a CubeCell field.