Shadowcast

Lua non recursive implementation of shadowcasting techinque for fast calculation of field of view. Original recursive algorithm by Björn Bergström description at Rogue Basin.

Current implementation allows simple luminance evaluation (not just FOV) and with some effort even light blending, see test example for instance (you will need luabox installed).

Shadowcast.new( absorption, [topology, [directions]] )

Create new luminance object. You must pass absorption 2d array where essentialy 0 means free space and 1 means wall. You can choose topology from the predefined set: Shadowcast.MANHATTAN, Shadowcast.EUCLIDEAN (which is the default) or Shadowcast.CHEBYSHEV. For now directions is limited to Shadowcast.DIRECTIONS_8.

Shadowcast.get( x, y )

Get luminance at the selected location. If x or/and y is/are out of bounds then function returns 0.

Shadowcast.insert( x, y, radius )

Insert new light source. Function returns newly created table, which could be used for the remove method. Note that if you alter the table fields, you must update the whole simulation.

Shadowcast.remove( source )

Remove the source from the simulation. If it's not present then nothing happens.

Shadowcast.update()

Fully update the whole light simulation. Note that when you insert/remove light sources luminance updated automatically and quite efficient, because only connected to the light source computations are made. Unfortunatly, because of the nature of compuataions with floating point after some iterations you will get rounding error. Using update sometimes while somehow expensive negates this error.