Empowerment: Sliding Ninjas - The Game Maker's Companion: Game Development - page 88

3. Turn Show Tiles back off and place one instance of each of the 16 different Ramps group

objects ( obj_ramp_u1 to obj_ramp_d8 ), as shown in the bottom left panel of Figure 4-14.
Also, delete the unneeded platform instances underneath the ramp as shown.

Figure 4-14. Adding ramp collision objects to the room

4. Turn Show Tiles back on and scroll to the second ramp over on the far right of the
room.
5. Carefully right-click on the two squares marked with blue crosses in the top right panel
of Figure 4-14 to delete the collision objects. Again, this will mark the boundaries of
the ramp for you when you turn the tiles off.
6. Turn Show Tiles back off again and place instances of the first eight different Ramps
group objects ( obj_ramp_u1 to obj_ramp_u8 ), as shown in the bottom right panel of
Figure 4-14. Also, delete the unneeded platform instances and add two extra to fill the
gap on the right-hand side of the ramp as shown.
Believe it or not, probably the hardest part of ramps is finished! If you play the game now,
you will see that you can already collide with ramps, as the hierarchy of parents means that all
these different ramp objects are eventually a kind of obj_solid . However, the general-purpose
obj_solid collision events are not always suitable for ramps. The one in obj_zool_land simply
brings Zool to a halt on rising ramps, preventing him from walking up them. The sliding
mechanism in the collision event of obj_zool_air can cause Zool to slide uncontrollably down
falling ramps as well. Fortunately, we can simply add collision events between these state objects
and obj_ramp in order to handle this specific case differently from other solid objects.

Adding Specific Collision Events for Ramp Objects
1. Reopen obj_zool_land and create a Collision event with obj_ramp . Include a Set

Variable action ( control tab) that sets the Variable y Relative to -speed . This moves
Zool up by a distance equal to the speed he is traveling. The faster Zool is moving, the
further he may have moved inside the ramp during the collision, so the further he
needs to move up in order to be above the surface again (see Figure 4-15). This
method should work for angles up to and including 45 degrees.