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 |                        Laser Spirography Model                        |
 |                         Technical Information                         |
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 Introduction...
      This file explains how each option presented by the Parameters
 dialog box affects the output.  Contained also is specific information on
 how this program produces the output pattern.
  
 Plotting Algorithm...
      This program calculates the position of each point plotted in the output 
 window through the use of vector addition.  The program multiplies the
 sine of a mirror's angle of tilt by the distance to the next mirror or to
 the wall to find the length of the vector for that mirror.  The angle is
 simply the current position of the corresponding motor.  After the
 vectors for all three mirrors have been calculated, they are added using
 a simplified method of vector addition.  The result is converted to a
 rectangular coordinate system and then offset by the coordinates of a
 point centered in the output window.  The point is then plotted and the
 motor positions incremented according to their specified speed and
 direction. The program then loops back to the start.
 
 Mirror Angles...
      This option allows the user to change the angle at which a mirror 
 is mounted on the motor shaft.  The larger the angle, the greater effect
 the corresponding motor's position will have on the overall output
 pattern.  The angle is specified in degrees off of perpendicular.
 
 Distances...
      This option grants the user control over the placement of the
 mirrors.  The user has control over the distance from mirror A to mirror
 B, from mirror B to mirror C, and from mirror C to the wall on which the
 pattern is to be displayed (output window).  The greater the distance
 from one mirror to the next (or to the wall), the greater effect the
 corresponding motor's position will have on the overall output pattern.
 The distances are specified in relative units.  Exact measurements would
 be meaningless due to variations in screen size from monitor to monitor.
 
 Default Motor Positions...
      This parameter allows the user to specify the starting positions of
 the three motors.  There are two main reasons for using this feature.
 First, the user may wish to synchronize the rotation of two motors but
 in different positions.  Secondly, the user may find it convenient to
 have the ability to initiate the viewing of a pattern at a point along
 its course other than the default starting point.  Note that unless two
 or more motors are synchronized, changing these parameters will have no
 effect on the output pattern other than to change its starting point.
 
 Concurrently Displayed Points...
      This controls the size of the point erase buffer.  As each point is
 plotted its coordinants are stored in the point erase buffer.  The point
 in the adjacent buffer cell is deleted immediately afterward.  Therefore,
 the larger the buffer, the longer a point is displayed and the more
 points are on the screen at a time.
 
                                 Chris Gadda
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EOT