I have a simple particle game, where all the particles are arranged in a grid. This game is for touch devices so to take advantage of it I am trying to have a multitouch gravity field thing going on.

Basically I am trying to get it so that each finger is basically a well in an otherwise non existent gravity field. That way the particles are pulled towards a finger.

My problem is I don't even know where to begin with these calculations, I have tried averaging a particles distance to each finger, its direction to each finger and nothing seems to work nicely!

I have seen other games do this. What does the math for it look like?


1 Answer 1


This is in no way a complete answer.

What you could try is: for each finger touching the interface, you calculate the distance and direction of each particle from the touch point.

With the distance, you compute a force (use x as input, and have y result in something based on a logarithm or square function: the closer to the well, the stronger the force).

Add the velocity, composed of the direction and the force, to the particle.

Repeat for each finger!

  • \$\begingroup\$ How do you avoid having more forces when their are more fingers? \$\endgroup\$
    – J.Doe
    May 27, 2016 at 1:52
  • 1
    \$\begingroup\$ You don't! 2 fingers -> 2 wells -> twice the attracting force! Particles caught in the middle should stay still! \$\endgroup\$
    – Vaillancourt
    May 27, 2016 at 1:54

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