/// <summary>
/// Tests the tile for a collision. Returns via out the position in world space where the collision occured.
/// </summary>
/// <returns>The tile collision.</returns>
/// <param name="tile">Tile.</param>
/// <param name="edgeToTest">the opposite side of movement, the side the leading edge will collide with</param>
/// <param name="perpindicularPosition">Perpindicular position.</param>
/// <param name="leadingPosition">Leading position.</param>
/// <param name="shouldTestSlopes">Should test slopes.</param>
/// <param name="collisionResponse">Collision response.</param>
bool TestTileCollision(TiledTile tile, Edge edgeToTest, int perpindicularPosition, int leadingPosition, bool shouldTestSlopes, out int collisionResponse)
{
collisionResponse = leadingPosition;
// one way platforms are only collideable from the top when the player is already above them
if (tile.IsOneWayPlatform())
{
// only the top edge of one way platforms are checked for collisions
if (edgeToTest != Edge.Top)
{
return(false);
}
// our response should be the top of the platform
collisionResponse = TiledMap.TileToWorldPositionX(tile.Y);
return(_boxColliderBounds.Bottom <= collisionResponse);
}
var forceSlopedTileCheckAsWall = false;
// when moving horizontally the only time a slope is considered for collision testing is when its closest side is the tallest side
// and we were not intesecting the tile before moving.
// this prevents clipping through a tile when hitting its edge: -> |\
if (edgeToTest.IsHorizontal() && tile.IsSlope() && tile.GetNearestEdge(leadingPosition) == tile.GetHighestSlopeEdge())
{
var moveDir = edgeToTest.OppositeEdge();
var leadingPositionPreMovement = _boxColliderBounds.GetSide(moveDir);
// we need the tile x position that is on the opposite side of our move direction. Moving right we want the left edge
var tileX = moveDir == Edge.Right ? TiledMap.TileToWorldPositionX(tile.X) : TiledMap.TileToWorldPositionX(tile.X + 1);
// using the edge before movement, we see if we were colliding before moving.
var wasCollidingBeforeMove = moveDir == Edge.Right ? leadingPositionPreMovement > tileX : leadingPositionPreMovement < tileX;
// if we were not colliding before moving we need to consider this tile for a collision check as if it were a wall tile
forceSlopedTileCheckAsWall = !wasCollidingBeforeMove;
}
if (forceSlopedTileCheckAsWall || !tile.IsSlope())
{
switch (edgeToTest)
{
case Edge.Top:
collisionResponse = TiledMap.TileToWorldPositionY(tile.Y);
break;
case Edge.Bottom:
collisionResponse = TiledMap.TileToWorldPositionY(tile.Y + 1);
break;
case Edge.Left:
collisionResponse = TiledMap.TileToWorldPositionX(tile.X);
break;
case Edge.Right:
collisionResponse = TiledMap.TileToWorldPositionX(tile.X + 1);
break;
}
return(true);
}
if (shouldTestSlopes)
{
var tileWorldX = TiledMap.TileToWorldPositionX(tile.X);
var tileWorldY = TiledMap.TileToWorldPositionX(tile.Y);
var slope = tile.GetSlope();
var offset = tile.GetSlopeOffset();
// calculate the point on the slope at perpindicularPosition
collisionResponse = (int)(edgeToTest.IsVertical() ? slope * (perpindicularPosition - tileWorldX) + offset + tileWorldY : (perpindicularPosition - tileWorldY - offset) / slope + tileWorldX);
var isColliding = edgeToTest.IsMax() ? leadingPosition <= collisionResponse : leadingPosition >= collisionResponse;
// this code ensures that we dont consider collisions on a slope while jumping up that dont intersect our collider.
// It also makes sure when testing the bottom edge that the leadingPosition is actually above the collisionResponse.
// HACK: It isn't totally perfect but it does the job
if (isColliding && edgeToTest == Edge.Bottom && leadingPosition <= collisionResponse)
{
isColliding = false;
}
return(isColliding);
}
return(false);
}
