JS/NOTES/TILTEX

        //|/////////////////:DIAGRAM[SC[DIA_TILTEX]]:|//
        //|                                          |//
        //| Working out logic using a 4x4 tilemap:   |//
        //|                                          |//
        //| TILE[ 0 ]: ( 0 + 0.5 ) / 4 === 0.125     |//
        //| TILE[ 1 ]: ( 1 + 0.5 ) / 4 === 0.375     |//
        //| TILE[ 2 ]: ( 2 + 0.5 ) / 4 === 0.625     |//
        //| TILE[ 3 ]: ( 3 + 0.5 ) / 4 === 0.875     |//
        //|                                          |//
        //| |<----- 4 pixels / texels ----->|        |//
        //| +---+---+---+---+---+---+---+---+        |//
        //| |       |       |       |       |        |//
        //| +   0   +   1   +   2   +   3   + <<<<<  |//
        //| |       |       |       |       |    ^^  |//
        //| +---+---+---+---+---+---+---+---+    ^^  |//
        //| ^   ^  .25  ^  0.5  ^  .75  ^   ^    ^^  |//
        //| |   |       |       |       |   |    ^^  |//
        //| | 0.125   0.375   0.625   0.875 |    ^^  |//
        //| |                               |    ^^  |//
        //| 0<--WEBGL_MAPPED_RANGE_0_TO_1-->1    ^^  |//
        //|                                      ^^  |//
        //|                [ TILE_COORDINATES >>>^^] |//
        //|                (If each pixel encodes  ) |//
        //|                (a tile value on tilemap) |//
        //|                                          |//
        //|/////////////////:DIAGRAM[SC[DIA_TILTEX]]:|//


        TileCoord To TexelCoord Formula:
        ( for use inside a GLSL shader)

        //: tile_coord_x: 0-indexed integer tile
        //:               coordinate on x-axis.
        //: img_wid: width of image used to encode
        //:          tile values. Also our texture we
        //:          are sampling from.
        function TileCoord_TO_TexelCoord_X(
            tile_coord_x
        ,   img_wid
        ){
              return(  (tile_coord_x + 0.5 ) / img_wid );
              //: Divided by "img_wid" and NOT "img_wid - 1".
        };;