Used by the routine at DRAW_CELLS.

What stands in front of the knight is not drawn as walls, which would hide him: the drawing order (DRAW_CELLS) calls this for his own cell and the three nearer the viewer -- one less in V, one more in U, and both -- and for those only the line where the building's walls meet the ground is drawn, all the way round. The two near faces come from the building definition for this view (OUTLINE_NEAR_FACES), and the two far ones from the definition for the other view, which describes those same walls seen from the other side: from the right-hand corner leftwards, up the screen along one face and down along the other, each column's edge through DRAW_EDGE with C set to 1. Each tile has an edge picture under it (TILE_EDGES): a plain line for a wall, or a stub at one end for a tile with an archway, and C = 1 swaps which end's stub, since those faces are seen from behind. An archway in a wall so leaves a gap in its outline.

Open ground (type 0) has no building. Drawn with OR, and not through the column claims of DRAW_WALLS's walls. Measured: with this routine made to return at once, the white lines on the ground in front of the knight were gone, and with DRAW_WALLS returning at once instead, the walls behind him.