Drawing planets: PLS5

       Name: PLS5                                                    [Show more]
       Type: Subroutine
   Category: Drawing planets
    Summary: Calculate roofv_x / z and roofv_y / z
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * PL9 (Part 2 of 3) calls PLS5


 Calculate the following divisions of a specified value from one of the
 orientation vectors (in this example, roofv):

   (XX16+2 K2+2) = roofv_x / z

   (XX16+3 K2+3) = roofv_y / z


 Arguments:

   X                    Determines which of the INWK orientation vectors to
                        divide:

                          * X = 15: divides roofv_x and roofv_y

                          * X = 21: divides sidev_x and sidev_y

   INWK                 The planet's ship data block


.PLS5

 JSR PLS1               ; Call PLS1 to calculate the following:
 STA K2+2               ;
 STY XX16+2             ;   K+2    = |roofv_x / z|
                        ;   XX16+2 = sign of roofv_x / z
                        ;
                        ; i.e. (XX16+2 K2+2) = roofv_x / z
                        ;
                        ; and increment X to point to roofv_y for the next call

 JSR PLS1               ; Call PLS1 to calculate the following:
 STA K2+3               ;
 STY XX16+3             ;   K+3    = |roofv_y / z|
                        ;   XX16+3 = sign of roofv_y / z
                        ;
                        ; i.e. (XX16+3 K2+3) = roofv_y / z
                        ;
                        ; and increment X to point to roofv_z for the next call

 RTS                    ; Return from the subroutine