Bounce around the screen

godmoney

How can I make an actor bounce around the screen?
As an example - I want the actor to move right, while bouncing

SolarPepperStudios

Turn bounciness to 1 and then in the actor say:
- accelerate in direction 0 relative to scene at a speed of (whatever you want)
Then in your scene make a floor so that the actor will collide with it (therefore making it bounce) and turn gravity on to about 250
Then in your actor tell it to collide with the floor actor

godmoney

Thank you very much for your help.
My problem is the global gravity parameter.
I want a few different actors, all with different bouncing height.

tatiang

You can set your own gravity for each actor using Accelerate direction 270 (relative to scene) at whatever speed you want.

godmoney

I uploaded a video demonstrating my problem. The bouncing looks weird and get stuck in wrong places.

Here's the link:


Here are the details:

1. The scene has left boundary actor and right boundary
2. The Ball actor has the following rules:
2.1 When it hits the left or right boundaries it changes direction
2.2. It collides (and bounces) with the floor, left boundary and right boundary
2.3. It has Change Velocity rule of Speed 100 and the direction
2.4 It has Accelerate with Direction 270 and Acceleration of 350

tatiang

What rule/behaviors are you using for the "changes direction" part?

godmoney

I have an integer attribute called direction. 1 is right and 0 is left.
When the ball collides with the left boundary it changes the direction to 1 and collision with the right boundary changes the direction to 0.
Then, if Direction = 1 I change velocity to Direction 0 and Speed 100.
Otherwise I change Direction to 180 and Speed 100.

tatiang

Those rules will indeed change the direction but you're taking a ball that is bouncing up and to the right (for example) and making it bounce off at a right angle to the wall. That's not how a ball bounces... it bounces off the wall, goes up slightly, and then gravity brings it down. Similarly, a ball that bounces on its way down will not bounce off the wall perpendicular to the wall but will instead keep going down as it changes directions.

If you use the ball's linear x and y to determine its directional path (I think you use vectorToAngle) you should be able to have it bounce off at a 90° angle to the path instead of just 0° or 180°.

You may have to add or subtract 90° depending on how the ball is bouncing:



And I guess really that's a simplified way of thinking of it:

godmoney

Wow - thank you very much for the very detailed explanation!
Problem is - I'm not sure how to use it ...

What should I do with the linear x and y parameters?

tatiang

Well, I worked out a formula that I think works for each case (ball travelling up-right, up-left, down-right, and down-left): 360-[path angle of ball] Hmm, no that's not it.

The trick is to get the angle the ball is travelling. By linear x and y I meant self.motion.linear velocity.x (and y). The formula for the path angle of the ball is vectorToAngle(self.motion.linear velocity.x,I created a change attribute that sets self.image to main actor attack ( boolean attribute I created under "game").

tatiang

Here's an imperfect demo. There's probably an easier way to do all this!

godmoney

I need to add or subtract 90 according to the ball's direction (up or down). How do I know if it's moving up or down?

godmoney

Looks like just adding 90 works just fine... I think....

godmoney

And now it doesn't work... how weird...

godmoney

And it's getting even weirder... seems like what worked before, and works pretty good now is: vectorToAngle( self.Motion.Linear Velocity.X , self.Motion.Linear Velocity.Y (+90
which looks like a mistake... but it works...

RThurman

Trust the physics engine! Use collide behaviors (in the ball) for the floor and walls. Change the ball to circular collision shape. Work on bounciness, friction and drag (for walls, floor, and ball) until everything feels like it should.