How to decrease velocity constantly?

Question

I am developing a golf game using the GameSalad framework for iPhone. I have one attribute named speed of type integer with value 5000. I also have one boolean attribute named speedControl which is initially false.

When the ball is pressed and its sppedControl is true, I accelerate it with game.speed i.e. 5000.

Now I want to decrease the speed of the ball every 0.5 seconds, so i added a timer behavior and set it to every 0.5 seconds. Every tick of the timer, I set the CHANGE ATTRIBUTE game.speed to game.speed-300. but it's not working.

Sorry, I have no reputation, therefore I can't send you screenshots.

Please help me. I am very new to GameSalad and this is my first project.

Answer 1

Why do you want to decrease the velocity every 0.5 seconds, rather than modelling the forces acting on the ball accurately (in a perfect world)? This is not too complicated and will be far more realistic.

Rather than setting a speed, consider taking into account initial velocity in both X and Y, a starting angle of elevation, and a direction. The articles here and here provide ways of taking that information calculating the ball's position at any specific time, t, which is the time since the person hit the ball. They also allow you to calculate the angle required to hit the ball at to hit the target which could be useful to apply a random offset to for bots depending on their difficulty setting.

Answer 2

The golf game I wrote worked as follows:

In between shots (i.e. when the ball is not moving), the game is using a standard UI event model to allow you to place and execute your shot.

During a shot (i.e. while the ball is in motion), UI event listeners are turned off, and a standard real-time game loop is turned on, to resolve all physics -- motion, friction on that motion, and collisions. As soon as the ball comes to a halt, that physics loop is turned off, and UI event listeners are once again switched on, so the player can line up their next shot.

As Martin Foot has said, you want motion modifiers to your ball (damping from rolling along the green, and also collision checks and resolutions) to be applied every tick of your game/physics loop, typically between 1 in 20 and 1 in 60 times per second. If you have other movable obstacles, then you will include processing of these, here.