Collision Detection with SAT: False Collision for Diagonal Movement Towards Vertical Tile-Walls?
- by Macks
Edit: Problem solved!
Big thanks to Jonathan who pointed me in the right direction. Sean describes the method I used in a different thread. Also big thanks to him! :)
Here is how I solved my problem:
If a collision is registered by my SAT-method, only fire the collision-event on my character if there are no neighbouring solid tiles in the direction of the returned minimum translation vector.
I'm developing my first tile-based 2D-game with Javascript. To learn the basics, I decided to write my own "game engine". I have successfully implemented collision detection using the separating axis theorem, but I've run into a problem that I can't quite wrap my head around.
If I press the [up] and [left] arrow-keys simultaneously, my character moves diagonally towards the upper left. If he hits a horizontal wall, he'll just keep moving in x-direction.
The same goes for [up] and [left] as well as downward-diagonal movements, it works as intended:
http://i.stack.imgur.com/aiZjI.png
Diagonal movement works fine for horizontal walls, for both left and right-movement
However: this does not work for vertical walls.
Instead of keeping movement in y-direction, he'll just stop as soon as he "enters" a new tile on the y-axis.
So for some reason SAT thinks my character is colliding vertically with tiles from vertical walls:
http://i.stack.imgur.com/XBEKR.png
My character stops because he thinks that he is colliding vertically with tiles from the wall on the right.
This only occurs, when:
Moving into top-right direction towards the right wall
Moving into top-left direction towards the left wall
Bottom-right and bottom-left movement work: the character keeps moving in y-direction as intended.
Is this inherited from the way SAT works or is there a problem with my implementation? What can I do to solve my problem?
Oh yeah, my character is displayed as a circle but he's actually a rectangular polygon for the collision detection.
Thank you very much for your help.
