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⌂ ∞ ▽ The Sentinel on the BBC Micro

Landscape: tileData

       Name: tileData                                                [Show more]
       Type: Variable
   Category: Landscape
    Summary: Altitude and shape data for landscape tiles
  Deep dive: Tile data
             Tile shapes

    Context: See this variable in context in the source code
 References: This variable is used as follows:
             * GetTileData uses tileData
             * GetTileViewAngles (Part 2 of 4) uses tileData




 The landscape in The Sentinel consists of a tiled area of 31x31 tiles, like an
 undulating chess board that's sitting on a table in front of us, going into
 the screen.

 The shape of the landscape is defined by the altitude of the corners of each
 tile, so that's a 32x32 grid of altitudes, one for each tile corner.

 The x-axis is along the front edge, from left to right, while the z-axis goes
 into the screen from front to back, away from us.

 This table contains one byte of data for each tile corner in the landscape.

 If there is no object placed on the tile, then the data contained in each byte
 is as follows:

   * The low nibble of each byte contains the tile shape, which describes the
     layout and structure of the landscape on that tile (0 to 15).

   * The high nibble of each byte contains the altitude of the tile corner in
     the front-left corner of the tile (i.e. the corner closest to the origin
     of the landscape). We call this tile corner the "anchor". The altitude is
     in the range 1 to 11, so the top nibble never has both bit 6 and 7 set.

 If there is an object placed on the tile, then the data contained in each byte
 is as follows:

   * Bits 0 to 5 contain the number of the object on the tile (0 to 63). If
     there are multiple objects stacked on the tile, this is the number of the
     object on the top of the stack.

   * Bits 6 and 7 of the byte are set.

 We can therefore test for the presence of an object on a tile by checking
 whether both bit 6 and 7 are set (as empty tiles have the tile altitude in the
 top nibble, and this is in the range 1 to 11).

 As each tile is defined by a tile corner and a shape, we tend to use the terms
 "tile" and "tile corner" interchangeably, depending on the context. That said,
 for tile corners along the furthest back and rightmost edges of the landscape,
 the shape data is ignored, as there is no landscape beyond the edges.

 See the GetTileShape routine for information on the different types of tile
 shape.



.tileData

 EQUB &00, &00, &00, &00, &00, &00, &00, &27    \ These values are workspace
 EQUB &29, &20, &27, &29, &29, &27, &20, &00    \ noise and have no meaning
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &20, &20, &20
 EQUB &20, &20, &20, &29, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &29, &29, &29
 EQUB &29, &29, &29, &29, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &29, &29, &29
 EQUB &29, &29, &29, &29, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &20, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &29, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &29, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &29, &29, &29
 EQUB &29, &29, &29, &29, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &27, &29, &28, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &20, &20, &20
 EQUB &29, &20, &20, &20, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &29, &20, &20
 EQUB &29, &20, &20, &29, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &27, &29, &28, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &29, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &28
 EQUB &29, &29, &28, &20, &29, &28, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &28, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &20, &20, &20
 EQUB &20, &20, &20, &29, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &29, &29, &29
 EQUB &29, &29, &29, &29, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &29, &20, &20
 EQUB &28, &20, &20, &29, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &20, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &29, &29, &29, &29, &29, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &28, &20, &20, &29, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &29
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &20, &20, &20
 EQUB &20, &20, &20, &20, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &20, &20, &20
 EQUB &20, &20, &20, &20, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &20, &20, &20
 EQUB &20, &20, &20, &20, &20, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &20
 EQUB &20, &20, &20, &20, &20, &20, &20, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00
 EQUB &00, &00, &00, &00, &00, &00, &00, &00