several objects being "pulled" into a single point

This is the situation:

several objects all over the screen, then they get "sucked" or "pulled" into a single point (it's like a black hole or it's like Magneto from X-Men attracting all metal objects from everywhere into himself).

How do I code the "sucking in/pulling in" effect?

If you are using physics, you can just apply force towards position on the objects. Recommended that you put them all in the same family first though.

Sumyjkl

I'm not using physics. any other method without using behaviors? or at least not using physics?

You can just move toward position. A formula could be used also to slow down over time.

For example (just a guess): move toward (x,y) distance of: distance / 200 or sqrt(distance)

Apart from that, you would need to use move at angle, with an angle starting from self, ending at the target location: angle(self.x,self.y,target.x,target.y)

a simple verlet integration scheme with decaying energy would work to get an almost physically accurate "gravity" effect.

you'll have to create a few instance variables, i put them in square brackets for clarity, i named the point which stuff moves towards point so its position would be point.x, point.y

{ for each object: }

• set [tempx] to: self.x
• set [tempy] to: self.y
• set object position to:

{

>X: self.x+(self.x-lastx)*0.95+(point.x-self.x)*0.1

>Y: self.y+(self.y-lasty)*0.95+(point.y-self.y)*0.1

}

• set [lastx] to: tempx
• set [lasty] to: tempy

you could also try something like:

{ for each object: }

• set [dist] to: distance( self.x , self.y , point.x , point.y )
• set [tempx] to: self.x
• set [tempy] to: self.y
• set object position to:

{

>X: self.x+(self.x-lastx)*0.95+(point.x-self.x)*1/dist

>Y: self.y+(self.y-lasty)*0.95+(point.y-self.y)*1/dist

}

• set [lastx] to: tempx
• set [lasty] to: tempy

or something like:

{ for each object: }

• set [dist] to: distance( self.x , self.y , point.x , point.y )
• set [tempx] to: self.x
• set [tempy] to: self.y
• set object position to:

{

>X: self.x+(self.x-lastx)*0.95+(point.x-self.x)*2/(dist^2)

>Y: self.y+(self.y-lasty)*0.95+(point.y-self.y)*2/(dist^2)

}

• set [lastx] to: tempx
• set [lasty] to: tempy

play with the constant multipliers that appear in these equations like *0.95, *0.1, *1, *2 to vary energy conservation, spring force, traction force, gravity strength respectively, try to do the same thing to the X Y equations or you'll get strange behavior.