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Simulate Bouncing

I have learned from a different discussion that you cannot get a very slow actor to bounce due to a Box2d rule, but is there any way to simulate bouncing using a rule? Maybe something using sin? Thanks!

Comments

  • tatiangtatiang Posts: 11,794Member, Sous Chef, PRO, Senior Sous-Chef

    I Googled bounce sin gamesalad and one of the top results was this:

    https://forums.gamesalad.com/discussion/comment/579115/#Comment_579115

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  • stan_mcginnisstan_mcginnis Posts: 18Member, BASIC

    This would work for up and down bouncing, but my actor is on a flat plane where there is no gravity and it can move any direction and bounce off any wall. Also, this actor just bounces around and cannot be controlled by the player. Most importantly, the velocity should stay the same the whole time, like in a pong game.

  • tatiangtatiang Posts: 11,794Member, Sous Chef, PRO, Senior Sous-Chef
    edited November 2018

    I'm no expert on GameSalad physics but I have coded a game where the actor reflects off of a wall to simulate a bounce, as you describe. I can't recall exactly how I did it (it was years ago) but I definitely used trig functions to calculate the reflection path based on the vector (direction) of the actor.

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  • RThurmanRThurman Posts: 2,824Member, Sous Chef, PRO

    If the actor collides with a vertical wall, multiply its xVelocity by -1.

    If the actor collides with a horizontal wall (a floor or ceiling), multiply its yVelocity by -1.

  • stan_mcginnisstan_mcginnis Posts: 18Member, BASIC

    Does this mean I have to make a seperate actor for walls and ceiling? I am willing do that if that is the only way.

  • RThurmanRThurman Posts: 2,824Member, Sous Chef, PRO

    Yes, thats probably the most straight forward way to do it.

    I suppose that if you know the boundaries, you can skip checking for collisions with actors. Instead you could just test for the actor's x,y position.

    When (self.position.x < 0) or (self.position.x > 1024) then multiply xVelocity by -1.

    When (self.position.y < 0) or (self.position.y > 768) then multiply yVelocity by -1.

  • stan_mcginnisstan_mcginnis Posts: 18Member, BASIC

    Thanks! The walls are not near the boundaries of the screen though so I will have to use your previous idea.

  • RThurmanRThurman Posts: 2,824Member, Sous Chef, PRO

    You are welcome! Glad it will help.

    By the way, you can still use the x,y position method even if the "bounce" boundaries are nowhere near the screen edge.

  • stan_mcginnisstan_mcginnis Posts: 18Member, BASIC

    Lots of levels are like a maze, there are walls everywhere so using the x,y position method would take forever, but implementing a vertical wall and a horizontal wall was not as hard as I thought.

  • RThurmanRThurman Posts: 2,824Member, Sous Chef, PRO

    Great! Glad its working like you want.

  • stan_mcginnisstan_mcginnis Posts: 18Member, BASIC

    However, there is one problem: corners. When the object hits a sharp corner, only one of the directional velocities is changed, and the bounce is not natural. Is there any way to fix this?

  • RThurmanRThurman Posts: 2,824Member, Sous Chef, PRO

    Hmmm.... not sure what might be happening. Its almost impossible for the actor to hit both edges at the exact same instant -- so its unlikely to be that.

    What does "the bounce is not natural" mean? Can you give more detail?

  • stan_mcginnisstan_mcginnis Posts: 18Member, BASIC

    I mean a corner that is facing inward compared to the actor, such as the actor hitting this L coming from below and to the left of the L. The actor will always go up left after hitting the corner, even if it hits the right side of the corner. If you still do not understand what i mean, I can send you a screenshot.

  • RThurmanRThurman Posts: 2,824Member, Sous Chef, PRO
    edited March 27

    I can guess that something like that might happen because of the vertical and horizontal walls overlapping in different ways.

    For example, in your outside "L", the the vertical "wall" might be underneath the horizontal "wall" so that their ends overlap each other. If both walls are the same color, it might look like the vertical "wall" goes all the way down to the bottom of the "L" but the actor is actually bouncing off the horizontal "wall" that is on top of it.

    Try rearranging which walls overlap at the outside corners and see it that makes a difference in the way the actor bounces. You might also want to color the horizontal walls differently than the vertical walls so you can see what is overlapping what.

    Then hopefully with some experimentation, you will be able to see why "the bounce is not natural".

  • stan_mcginnisstan_mcginnis Posts: 18Member, BASIC

    Thank you! This is definitely the issue, and although I can not fix it in this instance do to visual problems, it is good to know what the problem is.

  • RThurmanRThurman Posts: 2,824Member, Sous Chef, PRO

    You are welcome!

    I suppose you can try a quick fix by moving the bottom horizontal piece of the "L" one pixel down and one pixel to the right of its current location. That will make things bounce a little more 'normal'.

  • stan_mcginnisstan_mcginnis Posts: 18Member, BASIC
    edited June 25

    [deleted]

  • tatiangtatiang Posts: 11,794Member, Sous Chef, PRO, Senior Sous-Chef

    @stan_mcginnis You can only edit forum posts up to 24 hours after you post them.

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