Using objects is the right thing to do here. You can always create a spline
object and just:
spline.v.add(fd1)
Run
import vmath
type
Seg = array[4, Vec2]
Spline = object
t: seq[float32]
xy: seq[Vec2]
v: seq[Vec2]
a: seq[Vec2]
length: seq[float32]
proc bezier(segment: Seg, res: int): Spline =
let
t1 = 1 / float32(res)
t2 = t1 * t1
t3 = t2 * t1
b0 = segment[0]
b1 = segment[1]
b2 = segment[2]
b3 = segment[3]
a = -b0 + 3 * b1 + -3 * b2 + b3
b = 3 * b0 + -6 * b1 + 3 * b2
c = -3 * b0 + 3 * b1
var
d = b0
fd1 = a * t3 + b * t2 + c * t1 #initial velocity
fd2 = 6 * a * t3 + 2 * b * t2 #initial acceleration
fd3 = 6 * a * t3 #acceleration change
var spline = Spline()
spline.t = @[float32(0.0)]
spline.xy = @[d]
spline.v = @[fd1]
spline.a = @[fd2]
spline.length = @[length(d)]
for i in 1 .. res:
d += fd1
fd1 += fd2 #speed
fd2 += fd3 #acceleration
spline.t.add(float32(i)*t1)
spline.xy.add(d)
spline.v.add(fd1)
spline.a.add(fd2)
spline.length.add(length(d))
return spline
Run
