Move x pixels towards target

[pauls313]

This is probably a really stupid problem, but anyway:
I have a bullet, and I want it to move, let's say, 2 pixels towards a target every frame. I already know how to move it towards something, like this:
x = x + ((targetx - x) / 5)
But it obviously slows down over time. It's smooth

How can I move it an exact amount of pixels every frame?

[ken.athomos]

Is it okay for you to attach a .love file of the thing you're working on?

Anyways, I'm assuming that the bullet is moving downwards to the target based on your equation. Have you tried using dt? If so, what happens?

[pgimeno]

You need to normalize the vector that points from bullet to target.

Code: Select all

function normalize2d(x, y)
  if x == 0 and y == 0 then return 0, 0 end
  local length = math.sqrt(x*x + y*y)
  return x/length, y/length
end

...
  local dirx, diry = normalize2d(targetx - bulletx, targety - bullety)
  bulletx = bulletx + dirx * (dt * bulletspeed)
  bullety = bullety + diry * (dt * bulletspeed)

Normalizing a vector means to obtain a vector of length 1 that points in the same direction as the given one. That's exactly what you need, because that way, you can multiply it by the bullet speed, to obtain a bullet velocity vector that points in that direction.

Note in the above code, bulletspeed is in pixels/s, and dt is the delta time coming as a parameter in the love.update event.

[pauls313]

I tried your code but I get the error ""=" expected near "==" in line 22". The line 22 would be the second line in your code.

[zorg]

pgimeno's snippets are syntactically correct, so again, paste the relevant code part and the full error message at least. A screenshot would work too, probably.