How to correctly align with a pixel perfect collision detection?

[SHC]

I had recently used GameMaker to do a small platform game with my friends. I was surprised that it had this function move_contact_all(direction, speed). This starts moving the object towards a direction until a collision takes place. It is working pretty well. I can’t see even a single pixel gap between even two odd shaped objects. It moved perfectly. Any ideas how to implement that behaviour?

I’m really interested in making an application which demonstrates the same effect.

[Mac70]

If you are using OpenGL (LWJGL/JOGL) then you can use occlusion query. It gives only true or false, but this is enough in most cases.

[SHC]

I don’t think that it is fast enough. This the documentation for that function.

With this action you can move the instance in a given direction until a contact position with an object is reached. If there already is a collision at the current position the instance is not moved. Otherwise, the instance is placed just before a collision occurs. You can specify the direction but also a maximal distance to move. For example, when the instance is falling you can move a maximal distance down until an object is encountered. You can also indicate whether to consider solid object only or all objects. You typically put this action in the collision event to make sure that the instance stops in contact with the other instance involved in the collision.

How can this be so fast?

[SHC]

Not in OpenGL but I use this method to detect pixel perfect collisions. isPixelPerfectCollision(float x1, float y1, BufferedImage image1, float x2, float y2, BufferedImage image2). How can I align the object perfect to it?

Thanks.