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Maths (Arithmetic): PIX1

[BBC Micro disc version, Flight]

Name: PIX1 [Show more] Type: Subroutine Category: Maths (Arithmetic) Summary: Calculate (YY+1 SYL+Y) = (A P) + (S R) and draw stardust particle
Context: See this subroutine in context in the source code Variations: See code variations for this subroutine in the different versions References: This subroutine is called as follows: * STARS1 calls PIX1 * STARS2 calls PIX1 * STARS6 calls PIX1

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 (further away = smaller point)
.PIX1 JSR ADD \ 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 PIX1 to draw the stardust particle \ at (X1,Y1)