Intersect Boundary Event

[Valerio]

I create a sprite 2x2 pixel that moves up and down in a room.
I set the steps to 1 and the speed of the sprite to 1 pixel per step.
When the event Intersect Boundary occurs, the sprite invert the direction of movement.
The problem is this:
on the top side of the room, the sprite leaves the room of 1 pixel before reversing the direction (I think it's ok)
but on the down side of the room, the sprite leaves the room of 2 pixel before reversing the direction.

Why this difference ?

 

[johnwo]

What is your collision mask and sprite origin set to?

 

[Valerio]

Origin in the default position and Precise Collision Checking

 

[johnwo]

I did some testing, and experienced the same issue.

Simply using:

if ((y <= 0) or (x <= 0)) or
  ((y + sprite_height >= room_height) or (x + sprite_width >= room_width)) then {
    // Change direction
}

Gave a better result.

The behaviour of "Intersect Boundary" looked more like this:

if ((y < 0) or (x < 0)) or
  ((y + sprite_height > room_height) or (x + sprite_width > room_width))

This code is just a rough example, but it should work with little to no modification, depending on object speed ect.
Rewriting it for bbox would be a good idea.

Cheers!