t1mmos / syzygy Goto Github PK

p = (px, py): current player position
v = (vx, vx): offset to walk to in next frame

The check currently checks whether (px + vx, py) or (px, py +vy) is inside a wall and sets vx, vy or both to 0 accordingly. This nicely results in 'gliding' against a wall at lower speed. This collision detection works on nearly all situations. However, imagine a player facing the corner of a isolated wall block - block at grid position (x, y) and player is inside grid position (x - 1, y - 1). As he comes closer to the wall's corner, the checks will not trigger until he is actually at position (px +vx, py +vy) in which case both checks will trigger the next frame, but then it's too late - the player is inside the wall.

We need to check also against (px + vx, py + vy) if the available checks are not triggered (because 'gliding' occurs in that case), and choose a gliding direction to not be stuck at a corner.