3D geometry: SetObjectCoords (Part 7 of 11)

       Name: SetObjectCoords (Part 7 of 11)                          [Show more]
       Type: Subroutine
   Category: 3D geometry
    Summary: Pre-process feeding and flying aliens (objects 31, 32 and 33)
  Deep dive: 3D objects
    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file


.objc6

                        \ If we get here then the object ID is 31, 32 or 33

 LDX alienSlot-30,Y     \ If the slot for alien Y contains a negative number,
 BMI objc7              \ then the slot is empty, so jump to objc11 via objc7
                        \ to return from the subroutine

 LDA alienState,X       \ If the alien's state is >= 27, then it is heading for
 CMP #27                \ Acornsville, so jump to objc9 to process this object
 BCS objc9

 LDA alienObjectId,X    \ Set A to the object ID for this alien

 BPL objc5              \ If A is positive, jump to objc5 to set the object
                        \ coordinates and process this object

.objc7

 JMP objc11             \ Jump to objc11 to move on to the next alien in the
                        \ group (for object 30) or return from the subroutine
                        \ (for objects 31 to 33)

.objc8

 JMP objc12             \ Jump to objc12 to return from the subroutine