Version analysis of PIX1 - Elite on the 6502

This code appears in the following versions (click to see it in the source code):

Cassette, Disc (flight), Disc (docked), 6502 Second Processor, Master and Electron

Code variations between these versions are shown below.

       Name: PIX1
       Type: Subroutine
   Category: Maths (Arithmetic)
    Summary: Calculate (YY+1 SYL+Y) = (A P) + (S R) and draw stardust particle


 Calculate the following:

   (YY+1 SYL+Y) = (A P) + (S R)

 and draw a stardust particle at (X1,Y1) with distance ZZ.


 Arguments:

   (A P)                A is the angle ALPHA or BETA, P is always 0

   (S R)                YY(1 0) or YY(1 0) + Q * A

   Y                    Stardust particle number

   X1                   The x-coordinate offset

   Y1                   The y-coordinate offset

   ZZ                   The distance of the point, with bigger distances drawing
                        smaller points:

                          * ZZ < 80           Double-height four-pixel square

                          * 80 <= ZZ <= 143   Single-height two-pixel dash

                          * ZZ > 143          Single-height one-pixel dot


.PIX1

Code variation 1 of 1A variation in the labels only

Tap on a block to expand it, and tap it again to revert.

Cassette, Flight, Docked, 6502SP, Electron
Master
 JSR ADD                \ Set (A X) = (A P) + (S R)
 JSR ADDK               \ Set (A X) = (A P) + (S R)

 STA YY+1               \ Set YY+1 to A, the high byte of the result

 TXA                    \ Set SYL+Y to X, the low byte of the result
 STA SYL,Y

                        \ Fall through into PIXEL2 to draw the stardust particle
                        \ at (X1,Y1)