Ray-casting algorithm: Difference between revisions

Content added Content deleted

Inline

@@ Line 862: / Line 862: @@
 end program Pointpoly</lang>
+=={{header|Go}}==
+<lang go>package main
+import (
+    "math"
+    "fmt"
+)
+type xy struct {
+    x, y float64
+}
+type seg struct {
+    p1, p2 xy
+}
+type poly struct {
+    name  string
+    sides []seg
+}
+func inside(pt xy, pg poly) (i bool) {
+    for _, side := range pg.sides {
+        if rayIntersectsSegment(pt, side) {
+            i = !i
+        }
+    }
+    return
+}
+func rayIntersectsSegment(p xy, s seg) bool {
+    var a, b xy
+    if s.p1.y < s.p2.y {
+        a, b = s.p1, s.p2
+    } else {
+        a, b = s.p2, s.p1
+    }
+    for p.y == a.y || p.y == b.y {
+        p.y = math.Nextafter(p.y, math.Inf(1))
+    }
+    if p.y < a.y || p.y > b.y {
+        return false
+    }
+    if a.x > b.x {
+        if p.x > a.x {
+            return false
+        }
+        if p.x < b.x {
+            return true
+        }
+    } else {
+        if p.x > b.x {
+            return false
+        }
+        if p.x < a.x {
+            return true
+        }
+    }
+    return (p.y-a.y)/(p.x-a.x) >= (b.y-a.y)/(b.x-a.x)
+}
+var (
+    p1  = xy{0, 0}
+    p2  = xy{10, 0}
+    p3  = xy{10, 10}
+    p4  = xy{0, 10}
+    p5  = xy{2.5, 2.5}
+    p6  = xy{7.5, 2.5}
+    p7  = xy{7.5, 7.5}
+    p8  = xy{2.5, 7.5}
+    p9  = xy{0, 5}
+    p10 = xy{10, 5}
+    p11 = xy{3, 0}
+    p12 = xy{7, 0}
+    p13 = xy{7, 10}
+    p14 = xy{3, 10}
+)
+var tpg = []poly{
+    {"square", []seg{{p1, p2}, {p2, p3}, {p3, p4}, {p4, p1}}},
+    {"square hole", []seg{{p1, p2}, {p2, p3}, {p3, p4}, {p4, p1},
+        {p5, p6}, {p6, p7}, {p7, p8}, {p8, p5}}},
+    {"strange", []seg{{p1, p5},
+        {p5, p4}, {p4, p8}, {p8, p7}, {p7, p3}, {p3, p2}, {p2, p5}}},
+    {"exagon", []seg{{p11, p12}, {p12, p10}, {p10, p13},
+        {p13, p14}, {p14, p9}, {p9, p11}}},
+}
+var tpt = []xy{{5, 5}, {5, 8}, {-10, 5}, {0, 5}, {10, 5}, {8, 5}, {10, 10}}
+func main() {
+    for _, pg := range tpg {
+        fmt.Printf("%s:\n", pg.name)
+        for _, pt := range tpt {
+            fmt.Println(pt, inside(pt, pg))
+        }
+    }
+}</lang>
+Output:
+<pre>
+square:
+{5 5} true
+{5 8} true
+{-10 5} false
+{0 5} false
+{10 5} true
+{8 5} true
+{10 10} false
+square hole:
+{5 5} false
+{5 8} true
+{-10 5} false
+{0 5} false
+{10 5} true
+{8 5} true
+{10 10} false
+strange:
+{5 5} true
+{5 8} false
+{-10 5} false
+{0 5} false
+{10 5} true
+{8 5} true
+{10 10} false
+exagon:
+{5 5} true
+{5 8} true
+{-10 5} false
+{0 5} false
+{10 5} true
+{8 5} true
+{10 10} false
+</pre>
 =={{header|Haskell}}==
 <lang haskell>import Data.Ratio