Introduction

This is a module for handling collision with tile maps. It's very simple to use. Set up callbacks and create a handler object, which is used to resolve collision with a tile map.

Usage

Load the module:

tilecollider = require 'tilecollider'

Create a new collision handler:

handler = tilecollider(g,tw,th,c,h,s)

	g  - callback for tile lookup
	tw - width of a tile
	th - height of a tile
	c  - tile collision callback 
	h  - table of heightmaps for slope tiles
	s  - true if the top left of tile (0,0) is the origin [default]
	   - false if the top left of tile (1,1) is the origin

The handler has methods for resolving collision with a particular side. All tiles touching the area of a box are checked. After collision resolution, the functions return the new/old position.

x = handler:leftResolve  (x,y,w,h)
x = handler:rightResolve (x,y,w,h)
y = handler:bottomResolve(x,y,w,h)
y = handler:topResolve   (x,y,w,h)

Note: +x is to the right, +y is to the bottom

x - coordinate of left side of box
y - coordinate of top side of box
w - width of the box
h - height of the box

The following table describes which direction the box is pushed to resolve a side collision.

side     push
----     ----

left     right
right    left
bottom   up
top      down

Callbacks

The tile lookup function is used to retrieve the tile. The tile is then passed to the collision callback for collision checking. The collision callback must return true for the collision to be resolved.

tile = g(x,y)            - get the tile at specified coords 	
bool = c(side,tile,x,y)  - pass info to collision callback

Heightmaps (OPTIONAL)

Heightmaps are used for slope tiles. A slope collision is resolved by looking up height values in an array. The height values form the shape of the slope. A heightmap can be horizontal or vertical. A slope tile can have one or both. Horizontal heightmaps only resolve collisions with the left and right sides. Vertical heightmaps only resolve collisions with the bottom and top sides. A table of heightmaps is used to index the heightmaps of a tile. See below for the format.

format
------

h = 
{
	[tile]  = 
	{
		vertical   = {...},
		horizontal = {...},
	},
	
	[tile2] = ...
}

heightmap type         compatible sides
--------------         ----------------

vertical               top  & bottom
horizontal             left & right

ASCII ART EXAMPLE
=================
4x4 tile example

**Vertical Height Map**

vertical = {1,2,3,4}

"bottom"
4       |
3     | |
2   | | |
1 | | | |
  1 2 3 4

"top"
1 | | | |
2   | | |
3     | |
4       |
  1 2 3 4

**Horizontal Height Map**

horizontal = {1,2,3,4}

"left"
1 =
2 = =
3 = = =
4 = = = =
  1 2 3 4

"right"
1       =
2     = =
3   = = =
4 = = = =
  4 3 2 1