Making an actor swing in a circle around a point, using the accelerometer

owen_dennis

Here's a picture to help explain what I'm trying to do:

What I'd like the player to be able to do is use the accelerometer to swing the triangle around the circle. So if you tilt to the right, the triangle rotates around the edge of the circle toward the right. If it's closer to the bottom of the circle it will rotate around the bottom, if it's closer to the top it will rotate around the top. I've set up the offset for the triangle using the usual offset you see around the forums.

It's the swinging around and controlling the rotation that has me a little stuck. One version I tried was to simply constrain the triangle's rotation to vectortoangle(game.accelerometer.x,game.accelorometery). This, however, is a little jittery and I can't really control the speed with which the rotation happens, it just clicks into place around the circle.

The second method I tried is I had an invisible weight/actor that goes in the direction of the tilt and runs against invisible walls. Then the rotation of the triangle is constrained to the vectortoangle of where that weight is relative to the center of the circle. That method works great and I can control the speed easily, however, the weight sometimes gets caught or slows down as it hits a small corner found between the meeting of the walls. I also tried making a massive circular collision box but it slows down wheneter it his the corners of the polygons.

I guess another option would be to figure out a way to use gravity and then give the triangle some weight, then have the accelerometer control gravity?

I feel like there's something there with the first method I used, but I'm not sure exactly how to get there. I need to be able to adjust the speed and I need the triangle to swing around the circle depending on which side of the circle it's on, instead of just snapping to the other side. Does anyone have any ideas on this?

RThurman

This might help:

louistrudel

@owen_dennis said:Does anyone have any ideas on this?

Im not really sure what you are trying to do here
if you want to move an actor go around a Circle here is my way of doing it:

create a game angle attribute: Angle

Constrain
Self.PositionX = (Cos(Angle) * Radius)+X
Self.PositionY = (Sin(Angle) * Radius)+Y

Where
X= PositionX of the circle
Y = PositionY of the circle
Angle = the angle your actor is in the circle
Radius= speaks for itself

Then

just play with the angle (interpolate,use timers, loop it, use your imagination)

owen_dennis

@RThurman said:
This might help:

Thanks! That's the kind of thing I'm looking for! However, It seems to have the issue I've seen where if the triangle is at like 10 and then has to go to 350, it goes around the long way instead of just crossing through 0 to get there. Which is weird, cause that %360 trick is in there.

RThurman

OK -- use the following equation in the constrain rotation behavior:
self.Rotation +((((( self.downAngle - self.Rotation )+180)%360)-180).9).1

Socks

@RThurman said:
OK -- use the following equation in the constrain rotation behavior:
self.Rotation +((((( self.downAngle - self.Rotation )+180)%360)-180).9).1

self.Rotation +((((( self.downAngle - self.Rotation )+180)%360)-180)*.9)*.1

RThurman

Thanks @Socks -- I forgot that vanilla strips out some 'control' characters.

owen_dennis

@Socks @RThurman That's perfect! Thank you! I'm going to spend some time breaking down the math of what this means so I can understand what's going on, but it totally does exactly what I want it to. Thanks a lot!

RThurman

@owen_dennis -- you are welcome!

Most of it is the equation implements a 'negative feedback control system'.

The " +180)%360)-180 " part manipulates the number so that it passes through the 0-360 boundary cleanly.

The_Gamesalad_Guru

@RThurman said:
@owen_dennis -- you are welcome!

Most of it is the equation implements a 'negative feedback control system'.

The " +180)%360)-180 " part manipulates the number so that it passes through the 0-360 boundary cleanly.

@RThurman @Socks
I'm using this method as well but I need to build on it. I want to have multiple actors around the radius that move synchronously. How would I do this using the new COM feature or another method that adds to the current equation? I can do it using an oversized actor with a custom collision shape but custom collisions do not respect the overlap and collide condition and I need that.

Edit: I I figured out a solution but still interested in your options.

RThurman

Hm... I'd probably experiment with adding an offset to each actor. The offset would be how many degrees an actor needs to be from the original angle.

Probably something like:
self.Rotation +(((((self.downAngle-self.Rotation+offsetAngle)+180)%360)-180)*.9)*.1