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New developed Isle of Man maps; work on intersections.

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Simon Brooke 2020-06-29 21:36:23 +01:00
parent 48d9aacb69
commit 4161f4f04a
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GPG key ID: A7A4F18D1D4DF987
12 changed files with 58 additions and 40 deletions
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89
src/walkmap/edge.clj
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@ -115,14 +115,21 @@
(defn overlaps2d?
"True if the recangle in the x,y plane bisected by edge `e1` overlaps that
bisected by edge `e2`. It is an error if either `e1` or `e2` is not an edge."
[e1 e2]
bisected by edge `e2`. It is an error if either `e1` or `e2` is not an edge.
If `c1` is passed it should be the first coordinate of the plane of
projection on which the overlap is sought (default: `:x`); similarly `c2`
should be the second such coordinate (default: `:y`)."
([e1 e2]
(overlaps2d? e1 e2 :x :y))
([e1 e2 c1 c2]
(when (and (edge? e1) (edge? e2))
(and
(> (minimaxd e1 :x max) (minimaxd e2 :x min))
(< (minimaxd e1 :x min) (minimaxd e2 :x max))
(> (minimaxd e1 :y max) (minimaxd e2 :y min))
(< (minimaxd e1 :y min) (minimaxd e2 :y max)))))
(> (minimaxd e1 c1 max) (minimaxd e2 c1 min))
(< (minimaxd e1 c1 min) (minimaxd e2 c1 max))
(> (minimaxd e1 c2 max) (minimaxd e2 c2 min))
(< (minimaxd e1 c2 min) (minimaxd e2 c2 max))))))
(defn intersection2d
"The probability of two lines intersecting in 3d space is low, and actually
@ -140,38 +147,40 @@
It is an error, and an exception will be thrown, if either `e1` or `e2` is
not an edge."
[e1 e2]
(if (and (edge? e1) (edge? e2))
(when
(overlaps2d? e1 e2) ;; relatively cheap check
(if
(collinear2d? e1 e2)
;; any point within the overlap will do, but we'll pick the end of e1
;; which is on e2
(if (on2d? e2 (:start e1)) (:start e1) (:end e1))
;; blatantly stolen from
;; https://gist.github.com/cassiel/3e725b49670356a9b936
(let [x1 (:x (:start e1))
x2 (:x (:end e1))
x3 (:x (:start e2))
x4 (:x (:end e2))
y1 (:y (:start e1))
y2 (:y (:end e1))
y3 (:y (:start e2))
y4 (:y (:end e2))
denom (- (* (- x1 x2) (- y3 y4))
(* (- y1 y2) (- x3 x4)))
x1y2-y1x2 (- (* x1 y2) (* y1 x2))
x3y4-y3x4 (- (* x3 y4) (* y3 x4))
px-num (- (* x1y2-y1x2 (- x3 x4))
(* (- x1 x2) x3y4-y3x4))
py-num (- (* x1y2-y1x2 (- y3 y4))
(* (- y1 y2) x3y4-y3x4))
result (when-not (zero? denom)
(vertex (/ px-num denom) (/ py-num denom)))]
(when (and result (on2d? e1 result) (on2d? e2 result)) result))))
(throw (IllegalArgumentException.
(str
"Both `e1` and `e2` must be edges."
(map #(or (:kind %) (type %)) [e1 e2]))))))
([e1 e2]
(intersection2d e1 e2 :x :y :z))
([e1 e2 c1 c2 c3]
(if (and (edge? e1) (edge? e2))
(when
(overlaps2d? e1 e2) ;; relatively cheap check
(if
(collinear2d? e1 e2)
;; any point within the overlap will do, but we'll pick the end of e1
;; which is on e2
(if (on2d? e2 (:start e1)) (:start e1) (:end e1))
;; blatantly stolen from
;; https://gist.github.com/cassiel/3e725b49670356a9b936
(let [x1 (c1 (:start e1))
x2 (c1 (:end e1))
x3 (c1 (:start e2))
x4 (c1 (:end e2))
y1 (c2 (:start e1))
y2 (c2 (:end e1))
y3 (c2 (:start e2))
y4 (c2 (:end e2))
denom (- (* (- x1 x2) (- y3 y4))
(* (- y1 y2) (- x3 x4)))
x1y2-y1x2 (- (* x1 y2) (* y1 x2))
x3y4-y3x4 (- (* x3 y4) (* y3 x4))
px-num (- (* x1y2-y1x2 (- x3 x4))
(* (- x1 x2) x3y4-y3x4))
py-num (- (* x1y2-y1x2 (- y3 y4))
(* (- y1 y2) x3y4-y3x4))
result (when-not (zero? denom)
(vertex (/ px-num denom) (/ py-num denom)))]
(when (and result (on2d? e1 result) (on2d? e2 result)) result))))
(throw (IllegalArgumentException.
(str
"Both `e1` and `e2` must be edges."
(map #(or (:kind %) (type %)) [e1 e2])))))))