Maths (Geometry): SPS1

       Name: SPS1                                                    [Show more]
       Type: Subroutine
   Category: Maths (Geometry)
    Summary: Calculate the vector to the planet and store it in XX15
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * COMPAS calls SPS1
             * Main flight loop (Part 9 of 16) calls SPS1
             * TACTICS (Part 3 of 7) calls SPS1


 Other entry points:

   SPS1+1               A BRK instruction


.SPS1

 LDX #0                 ; Copy the two high bytes of the planet's x-coordinate
 JSR SPS3               ; into K3(2 1 0), separating out the sign bit into K3+2

 LDX #3                 ; Copy the two high bytes of the planet's y-coordinate
 JSR SPS3               ; into K3(5 4 3), separating out the sign bit into K3+5

 LDX #6                 ; Copy the two high bytes of the planet's z-coordinate
 JSR SPS3               ; into K3(8 7 6), separating out the sign bit into K3+8

                        ; Fall through into TAS2 to build XX15 from K3