
xSGE Lighting Library
*********************


Contents
^^^^^^^^

* xSGE Lighting Library

  * xsge_lighting Functions

xSGE is a collection of extensions for the SGE licensed under the GNU
General Public License.  They are designed to give additional features
to free/libre software games which aren't necessary, but are nice to
have.

xSGE extensions are not dependent on any particular SGE
implementation. They should work with any implementation that follows
the specification.

This extension provides a simple interface for lighting.


xsge_lighting Functions
=======================

xsge_lighting.project_light(x, y, sprite, image=0)

   Add a light to the current frame.  This must be called every frame
   "xsge_lighting.project_darkness()" is called to maintain the
   respective light.  This function should be called *before*
   "xsge_lighting.project_darkness()".

   Arguments:

   * "x" -- The horizontal location of the light relative to the
     room.

   * "y" -- The vertical location of the light relative to the room.

   * "sprite" -- The sprite to use as the light.  Black pixels are
     ignored, and all other colors make the appropriate pixel

   * "image" -- The frame of the sprite to use, where "0" is the
     first frame.

xsge_lighting.clear_lights()

   Remove all lights that have been projected by
   "xsge_lighting.project_light()".

xsge_lighting.project_darkness(z=100000, ambient_light=None, buffer=0)

   This function must be called every frame to maintain darkness.

   Arguments:

   * "z" -- The Z-axis position of the darkness in the room.
     Anything with a higher Z-axis value will not be affected.

   * "ambient_light" -- A "sge.gfx.Color" object indicating the
     color that should be applied as lighting to the entirety of the
     darkness.  Set to "None" for no ambient lighting.

   * "buffer" -- An extra portion of the room, in addition to what
     is covered by the room's views, to cover with darkness.  This can
     be used to prevent situations where movement of a view at the
     wrong time causes part of the view to not be properly covered in
     darkness.  To ensure maximum efficiency, this should be the
     smallest number possible, i.e. the maximum amount of view
     movement that can happen in a single frame.
