README

MagicTracks is a CAD-like program for use by Model Railroaders.

It is being developed using FreePascal and Lazarus.  Currently, the implementation
is limited to Windows due to the lack of certain primitives (specifically those
that allow rotation of text) in the Lazarus Component Library.  I intend to
remove that limitation, but not in the immediate future.

The top-level data object is a Drawing, many of which may be opened simultaneously.

Each Drawing consists of several layers, many of which may be viewed
simultaneously, one of which may be edited at any given time.

Each Layer consists of no or more drawing objects.

A drawing object may be a drawing primitive or a group of drawing objects.

Drawing primitives are 3-dimensional objects.  As of April 11, 2012 the
following Drawing Primitives are being developed:

          Rectangular Solid (generalization of a cube) - works without rotations
          Ellipsoid (generalization of a sphere) - under development
          Straight Line (from x0, y0, z0 to x1, y1, z1) - thinking about it
          Bezier Curves (in 3 dimensions) - in the headache stage.

I am taking an unusual path to developing the drawing primitives.  The active
layer has two "Canvases".  One canvas is the normal Lazarus (Delphi) drawing
canvas.  The second canvas has the same dimensions as the first, but the "pixels"
are pointers to the Drawing Object (last drawn) that occupies that position.
This makes the process of editing drawing objects much easier than if each
drawing object needed to be interrogated for each mouse movement.

As each drawing object (on the active layer) is drawn, the pixel value (color,
etc) is written to the drawing canvas and the object pointer is written to the
object pointer.  This means that the algorithm for identifying the pixels
must be separated from the internal canvas operations.  Consequently, I am
implementing Bresham's Line Drawing Algorithm and other similar algorithms
for spheres and Bezier curves.