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arc small stuff

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This commit is contained in:
Ryan Oldenburg 2021-01-22 10:31:04 -06:00
parent 9aafd87def
commit e676121ae3
1 changed files with 21 additions and 25 deletions
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46
src/pixie/paths.nim
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@ -875,56 +875,52 @@ proc arc*(path: Path) =
proc arcTo*(path: Path, x1, y1, x2, y2, r: float32) =
## Adds a circular arc to the path with the given control points and radius, connected to the previous point by a straight line.
var
x0 = path.at.x
y0 = path.at.y
x21 = x2 - x1
y21 = y2 - y1
x01 = x0 - x1
y01 = y0 - y1
l01_2 = x01 * x01 + y01 * y01
const epsilon = 1e-6.float32
const epsilon: float32 = 1e-6
if path.commands.len == 0:
# Is this path empty? Move to (x1,y1).
path.moveTo(x1, y1)
var r = r
if r < 0:
# Is the radius negative? Flip it.
r = -r
if path.commands.len == 0:
# Is this path empty? Move to (x1,y1).
path.commands.add(PathCommand(kind: Move, numbers: @[x1,y1]))
var
x21 = x2 - x1
y21 = y2 - y1
x01 = path.at.x - x1
y01 = path.at.y - y1
l01_2 = x01 * x01 + y01 * y01
elif not (l01_2 > epsilon):
# Or, is (x1,y1) coincident with (x0,y0)? Do nothing.
if not (l01_2 > epsilon):
# Is (x1,y1) coincident with (x0,y0)? Do nothing.
discard
elif not (abs(y01 * x21 - y21 * x01) > epsilon) or r == 0:
# // Or, are (x0,y0), (x1,y1) and (x2,y2) collinear?
# // Or, are (x0,y0), (x1,y1) and (x2,y2) colinear?
# // Equivalently, is (x1,y1) coincident with (x2,y2)?
# // Or, is the radius zero? Line to (x1,y1).
path.commands.add(PathCommand(kind: Line, numbers: @[x1, y1]))
path.at.x = x1
path.at.y = y1
path.lineTo(x1, y1)
else:
# Otherwise, draw an arc!
# Draw an arc
var
x20 = x2 - x0
y20 = y2 - y0
x20 = x2 - path.at.x
y20 = y2 - path.at.y
l21_2 = x21 * x21 + y21 * y21
l20_2 = x20 * x20 + y20 * y20
l21 = sqrt(l21_2)
l01 = sqrt(l01_2)
l:float32 = r * tan((PI - arccos((l21_2 + l01_2 - l20_2) / (2 * l21 * l01))) / 2)
l = r * tan((PI - arccos((l21_2 + l01_2 - l20_2) / (2 * l21 * l01))) / 2).float32
t01 = l / l01
t21 = l / l21
# If the start tangent is not coincident with (x0,y0), line to.
# If the start tangent is not coincident with path.at, line to.
if abs(t01 - 1) > epsilon:
path.commands.add(PathCommand(kind: Line, numbers: @[x1 + t01 * x01, y1 + t01 * y01]))
discard
path.lineTo(x1 + t01 * x01, y1 + t01 * y01)
path.at.x = x1 + t21 * x21
path.at.y = y1 + t21 * y21
path.commands.add(PathCommand(