Physics Joints - Learn SpriteBuilder for iOS Game Development - page 307

also work, it's best to avoid changing the anchor point whenever you can do so
by altering the node's position.
Now select the springboard_spring , and switch to the Item Physics tab. Check Enable
physics , and uncheck Affected by gravity and Allows rotation .
Unchecking Affected by gravity prevents gravity from influencing the spring. You deselect
this check box because you may want to use the spring as an upside down or sideways
spring, and gravity would only serve to decrease the force of an upward spring while in-
creasing it for a downward-oriented spring. Disabling rotation will prevent the spring
from rotating to the sides, especially when it hits an object. It's difficult enough to keep
the spring aligned to the same outward-facing direction without resorting to programming.
And let's not forget to define the springboard's collision shape. Keep in mind that the
spring's collision shape should encompass the shape of its child sprite, the board. Still, 10
points for the shape are plenty. (See Figure 9-18 .) Two points are spent to allow the sides
to give the player a slightly outward-oriented spin if the player misses the center of the
springboard.
Figure 9-18 . The shroom-shaped spring includes the board's collision shape. The zoom level is 8x, hence the
blurred image
As seen in Figure 9-18 , you should try to make the bottom of the spring as rectangular as
possible. That's the “bolt” part that should fit into the shaft defined by the spring-
board_metal as closely as possible.
Speaking of which: select the springboard_metal , go to the Item Physics tab to Enable
physics . Then change the body's type to Static . You can begin editing the shaft's collision
shape right away.