Bezier Path Generator

[TerryRitchie]

Has anyone worked with Bezier curves?

I'm attempting to write a path generator for items such as enemy ships, like when the ships form up in Galaga at the start of a level, or during a challenging stage.

The code below is a quick and dirty Bezier path maker. It works, but no matter what I set the variable Detail to the path comes up jagged, with a sort of stair step effect to it. Does anyone know how I can smooth this out if possible?

Code: (Select All)

TYPE POINT
    x AS INTEGER
    y AS INTEGER
END TYPE

DIM Curve(3) AS POINT
REDIM Path(0) AS POINT

DIM p AS POINT

Curve(0).x = 0
Curve(0).y = 479

Curve(1).x = 639
Curve(1).y = 239

Curve(2).x = 0
Curve(2).y = 239

Curve(3).x = 639
Curve(3).y = 0

SCREEN _NEWIMAGE(640, 480, 32)

Detail = .00001


FOR t = 0 TO 1 STEP Detail
    CurvePoint Curve(), p, t
    New = -1
    FOR i = 0 TO UBOUND(Path) - 1
        IF p.x = Path(i).x AND p.y = Path(i).y THEN
            New = 0
            EXIT FOR
        END IF
    NEXT i
    IF New THEN
        Path(UBOUND(Path)) = p
        REDIM _PRESERVE Path(UBOUND(Path) + 1) AS POINT
    END IF

    'PSET (p.x, p.y)
NEXT t

PSET (Path(0).x, Path(0).y)
FOR i = 1 TO UBOUND(Path) - 1
    LINE -(Path(i).x, Path(i).y)
NEXT i
PRINT UBOUND(Path)



SUB CurvePoint (c() AS POINT, p AS POINT, t AS SINGLE)

    'Quick and dirty Bezier point calculator
    'Note: only works for 4 points

    p.x = (1 - t) * (1 - t) * (1 - t) * c(0).x + 3 * (1 - t) * (1 - t) * t * c(1).x + 3 * (1 - t) * t * t * c(2).x + t * t * t * c(3).x
    p.y = (1 - t) * (1 - t) * (1 - t) * c(0).y + 3 * (1 - t) * (1 - t) * t * c(1).y + 3 * (1 - t) * t * t * c(2).y + t * t * t * c(3).y

END SUB