Flight model: AdjustTurn

       Name: AdjustTurn                                              [Show more]
       Type: Subroutine
   Category: Flight model
    Summary: Adjust the plane's turn rate
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * ApplyFlightModel (Part 6 of 7) calls AdjustTurn


 This routine adjusts the plane's turn rate by adding a 24-bit unsigned vector
 to each axis of the plane's turn rate. Specifically, it does the following for
 each of the three axes (x, y and z):

   (xTurnTop xTurnHi xTurnLo) += (dxTurnTop dxTurnHi dxTurnLo)

 so that's:

   [ xTurn ]   [ xTurn ]   [ dxTurn ]
   [ yTurn ] = [ yTurn ] + [ dyTurn ]
   [ zTurn ]   [ zTurn ]   [ dzTurn ]

 where (dxTurn dyTurn dzTurn) and (xTurn yTurn zTurn) are vectors made up of
 unsigned 24-bit numbers representing angles.


.AdjustTurn

 LDX #2                 \ Set a counter in X to work through the three axes (the
                        \ comments below cover the iteration for the x-axis)

.atur1

 LDA dxTurnLo,X         \ Set xTurn = xTurn + dxTurn
 CLC                    \
 ADC xTurnLo,X          \ starting with the low bytes
 STA xTurnLo,X

 LDA dxTurnHi,X         \ And then the high bytes
 ADC xTurnHi,X
 STA xTurnHi,X

 LDA dxTurnTop,X        \ And then the top bytes
 ADC xTurnTop,X
 STA xTurnTop,X

 DEX                    \ Decrement the loop counter to move to the next axis

 BPL atur1              \ Loop back until we have processed all three axes

 RTS                    \ Return from the subroutine