Eng:Object Repulsion

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Object Repulsion is the act of repulsing or repelling an object. Listed below are two methods of replicating this effect in Scratch.

Tip:	Please remember to adjust the scripts shown in this tutorial as necessary to best fit your project.

Velocity Method

The Velocity Method uses the following scripts to automatically make objects change their X and Y Velocity based upon their position. This script can go into any object that is being repelled. This method is more advanced than the next method, however this method is better in most situations.

Note:

Do not put this script into an object intended to be static (non-moving).

when green flag clicked
go to x: (0) y: (0)
set [y speed v] to (0)
set [x speed v] to (0)
forever
  if <([abs v] of (([x position v] of [Sprite1 v]) - ([x position v] of [Sprite2 v]))) < [50]> then
    if <([x position v] of [Sprite 2 v]) > (x position)> then
      change [x speed v] by (-0.1)
    end
    if <([x position v] of [Sprite 2 v]) < (x position)> then
      change [x speed v] by (0.1)
    end
  end
  if <([abs v] of (([y position v] of [Sprite1 v]) - ([y position v] of [Sprite2 v]))) < [50]> then
    if <([y position v] of [Sprite 2 v]) > (y position)> then
      change [y speed v] by (-0.1)
    end
    if <([y position v] of [Sprite 2 v]) < (y position)> then
      change [y speed v] by (0.1)
    end
  end
end

when green flag clicked
forever
  if on edge, bounce
  change x by (x speed)
  change y by (y speed)
  set [x speed v] to ((0.98) * (x speed))
  set [y speed v] to ((0.98) * (y speed))
end

An example can be seen here.

Direct Movement Method

The Direct Movement Method uses the scripts below to move and rotate based on its position. This method is basic, but very effective in doing its job.

Note:

This script can only be used in one sprite at a time unlike the velocity method.

when gf clicked
go to x: (0) y: (-1)
forever
   if <(distance to [Sprite2 v]) < [50]> then
      point towards [Sprite2 v]
      point in direction ((direction) - (4))
      move (10) steps
      if on edge, bounce

An example can be seen here.

See Also

• Object Attraction
• Simulating Gravity