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[Sokafootball]

Hello everyone,

I am a beginner game maker developer.

I am trying to create a moving horizontal platform for a platform 2d game in Game Maker.

I did some research and many developers use marks to stop the object from moving and changing its directions.

While i understand this perfectly works, i still want to understand why my code is not working.

In this example the platform should move between a space of 128 pixels at 2 pixels per step, with the center of that space being the x coordinate at the spot of creation.

My platform object has 2 events

------------------------

[Create]

///Speed, distance to travel and starting direction
movespeed = 2;
movedirection = 1; //choose starting direction, 1 for right -1 for left
traveldistance = 64;
startingx = x;

[Step]

destination = startingx + traveldistance * movedirection;
while (x != destination)
{
x += movedirection*movespeed;
}
movedirection *= -1;

-------------------------

What happen is that once the game starts the platform is blinking at ridiculous speed between the two edges of that 128 pixels space.

I am not sure, but it seems it's not just moving very very quickly, but it's actually teleporting back and forth.

Thanks for any help,



Laurent

[ThemsAllTook]

With the while loop in [Step], it looks like you've set it up to move completely to its destination every frame. Presumably, you'd want something more like this:

Code:

[Create]

///Speed, distance to travel and starting direction
movespeed = 2;
movedirection = 1; //choose starting direction, 1 for right -1 for left
traveldistance = 64;
startingx = x;
destination = startingx + traveldistance * movedirection;

[Step]

x += movedirection*movespeed;
if (x == destination) {
  movedirection *= -1;
  destination = startingx + traveldistance * movedirection;
}

That way, each time [Step] happens, the x coordinate will only be moved a little bit rather than continuing to move all the way to the destination. Note that I've moved the calculation of destination into [Create], and also put a recalculation of it inside the if statement in [Step].

Something to watch out for: If you ever need to move in non-integer increments, or your traveldistance isn't divisible by your movespeed, the == check for destination won't work and your platform will continue past its destination. Even when using only integers, it's safer to use some form of range check. Since there are two directions, it's a bit more to write, but something like this could do the job:

if ((movedirection == -1 && x <= destination) || (movedirection == 1 && x >= destination))

[Sokafootball]

Thank you so much!!! 

now it makes sense