Landscape: tileEdges

       Name: tileEdges                                               [Show more]
       Type: Variable
   Category: Landscape
    Summary: A table to map tile shapes and gaze vector direction to tile edges
    Context: See this variable in context in the source code
 References: This variable is used as follows:
             * FollowGazeVector (Part 4 of 5) uses tileEdges


 This table contains tile corner numbers from a tile:

      ^           [1]  [2]
      |
      |           [0]  [3]
   z-axis
    into
   screen      x-axis from left to right --->

 Each tile corner number represents an edge from the number to the number + 1,
 so 1 represents the edge from corner 1 to corner 2, for example.

 The table is used to work out which edge should be chosen for the calculation
 in the FollowGazeVector routine, where we work out whether the gaze vector is
 hitting a tile slope in a tile with two horizontal edges.

 See part 4 of the FollowGazeVector routine for details of how this table
 works.


.tileEdges

 EQUB 0, 3              \ Left and bottom edges (G = 0)
                        \
                        \ First entry (left edge) for xCoordLo < zCoordLo
                        \
                        \ Second entry (bottom edge) for xCoordLo >= zCoordLo

 EQUB 1, 0              \ Top and left edges (G = 1)
                        \
                        \ First entry (top edge) for ~xCoordLo < zCoordLo
                        \
                        \ Second entry (left edge) for ~xCoordLo >= zCoordLo

 EQUB 1, 2              \ Top and right edges (G = 2)
                        \
                        \ First entry (top edge) for xCoordLo < zCoordLo
                        \
                        \ Second entry (right edge) for xCoordLo >= zCoordLo

 EQUB 2, 3              \ Right and bottom edges (G = 3)
                        \
                        \ First entry (right edge) for ~xCoordLo < zCoordLo
                        \
                        \ Second entry (bottom edge) for ~xCoordLo >= zCoordLo