|y1||the iterations (per step) that the physics system will perform|
Everything in GameMaker: Studio is based around steps
and, normally, each event will only happen once per step. However,
to get the necessary precision with the physics functions they are
made to do several calculations each step which are called
"iterations" the number of which are controlled by this function.
The default number for the physics system is 10, but this can be
changed to higher or lower depending how many times you want the
physics to calculate each step, but it is recommended that you set
this no lower than 5 and no higher than 30. You should also be
aware that this function is dependant on the physics_world_update_speed
The code above sets the physics world in the current room to perform calculations 20 times a step.