Drawing ships: FACE

       Name: FACE                                                    [Show more]
       Type: Macro
   Category: Drawing ships
    Summary: Macro definition for adding faces to ship blueprints
  Deep dive: Ship blueprints
    Context: See this macro in context in the source code
 References: This macro is used as follows:
             * SHIP_CANISTER uses FACE
             * SHIP_CHAMELEON uses FACE
             * SHIP_DODO uses FACE
             * SHIP_ESCAPE_POD uses FACE
             * SHIP_MAMBA uses FACE
             * SHIP_MORAY uses FACE
             * SHIP_OPHIDIAN uses FACE
             * SHIP_TRANSPORTER uses FACE
             * SHIP_VIPER uses FACE


 The following macro is used to build the ship blueprints:

   FACE normal_x, normal_y, normal_z, visibility

 See the deep dive on "Ship blueprints" for details of how faces are stored
 in the ship blueprints, and the deep dive on "Drawing ships" for information
 on how faces are used to draw 3D wireframe ships.


 Arguments:

   normal_x             The face normal's x-coordinate

   normal_y             The face normal's y-coordinate

   normal_z             The face normal's z-coordinate

   visibility           The visibility distance, beyond which the edge is always
                        shown


MACRO FACE normal_x, normal_y, normal_z, visibility

 IF normal_x < 0
  s_x = 1 << 7
 ELSE
  s_x = 0
 ENDIF

 IF normal_y < 0
  s_y = 1 << 6
 ELSE
  s_y = 0
 ENDIF

 IF normal_z < 0
  s_z = 1 << 5
 ELSE
  s_z = 0
 ENDIF

 s = s_x + s_y + s_z + visibility
 ax = ABS(normal_x)
 ay = ABS(normal_y)
 az = ABS(normal_z)

 EQUB s, ax, ay, az

ENDMACRO