[geom] Split shapes into individual files; includes a fix to Tri.Cont…

…ains

Contains didn't properly account for collinearity.

internal/geom/rect.go

@@ -0,0 +1,27 @@
+package geom
+
+import "fmt"
+
+// Rect represents a rectangle
+type Rect struct {
+	TL P // top-left vertex of the rectangle
+	BR P // bottom-right vertex of the rectangle
+}
+
+func (r Rect) String() string {
+	return fmt.Sprintf("{geom.P{%.02f,%.02f},geom.P{%.02f,%.02f}}", r.TL.X, r.TL.Y, r.BR.X, r.BR.Y)
+}
+
+func (r Rect) SVG() string {
+	width := r.BR.X - r.TL.X
+	height := r.BR.Y - r.TL.Y
+	return fmt.Sprintf(`<rect class="rect" x="%f" y="%f" width="%f" height="%f" style="fill: lightgrey; stroke: black;" />`, r.TL.X, r.TL.Y, width, height)
+}
+
+func (r Rect) Width() float64 {
+	return r.BR.X - r.TL.X
+}
+
+func (r Rect) Height() float64 {
+	return r.BR.Y - r.TL.Y
+}

internal/geom/segment.go

@@ -0,0 +1,18 @@
+package geom
+
+import "fmt"
+
+type Segment struct {
+	A, B P
+}
+
+func (seg Segment) SVG() string {
+	return fmt.Sprintf(`<path d="M %.2f,%.2f %.2f,%.2f" stroke="blue" />`, seg.A.X, seg.A.Y, seg.B.X, seg.B.Y)
+}
+
+func (seg Segment) Other(v P) P {
+	if seg.A == v {
+		return seg.B
+	}
+	return seg.A
+}

internal/geom/shortest.go

@@ -17,7 +17,6 @@ func Shortest(p1, p2 P, rects []Rect) []P {
 	// find start and end triangles
 	var start, end Tri
 	for _, t := range ts {
-		// fmt.Println(t.String())
 		if t.Contains(p1) {
 			start = t
 		}

internal/geom/triangle.go

@@ -0,0 +1,52 @@
+package geom
+
+import "fmt"
+
+// Tri represents a triangle
+type Tri struct {
+	ID      int
+	A, B, C P
+}
+
+func (t Tri) SVG() string {
+	return fmt.Sprintf(`<path d="M %.2f,%.2f %.2f,%.2f %.2f,%.2f Z" stroke="blue" fill="none"/>`, t.A.X, t.A.Y, t.B.X, t.B.Y, t.C.X, t.C.Y)
+}
+
+func (t Tri) Barycenter() P {
+	bx := (t.A.X + t.B.X + t.C.X) / 3
+	by := (t.A.Y + t.B.Y + t.C.Y) / 3
+	return P{bx, by}
+}
+
+func (t Tri) Contains(p P) bool {
+	s := 0
+	e := []P{t.A, t.B, t.C}
+	for i := range 3 {
+		or := orientation(e[i%3], e[(i+1)%3], p)
+		if or == cln {
+			q, r := e[i%3], e[(i+1)%3]
+			return p.X >= min(q.X, r.X) && p.X <= max(q.X, r.X) &&
+				p.Y >= min(q.Y, r.Y) && p.Y <= max(q.Y, r.Y)
+		}
+
+		if or != cw {
+			s++
+		}
+	}
+	return s == 3 || s == 0
+}
+
+func (t Tri) OrderedSide(i int) Segment {
+	e := []P{t.A, t.B, t.C}
+	a, b := e[i%3], e[(i+1)%3]
+	if a.X < b.X {
+		return Segment{a, b}
+	}
+	if b.X < a.X {
+		return Segment{b, a}
+	}
+	if a.Y < b.Y {
+		return Segment{a, b}
+	}
+	return Segment{b, a}
+}

internal/geom/triangle_test.go

@@ -0,0 +1,25 @@
+package geom
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTri(t *testing.T) {
+	t.Run("contains", func(t *testing.T) {
+		cases := []struct {
+			t Tri
+			p P
+		}{
+			{Tri{0, P{0, 0}, P{20, 0}, P{20, 50}}, P{10, 5}},
+			{Tri{1, P{19.2, 44.7}, P{142.6, 16.5}, P{228, 212}}, P{28.6, 46.6}},
+			{Tri{2, P{20, 20}, P{200, 20}, P{300, 40}}, P{197.7, 27}},
+			{Tri{3, P{50, 10}, P{80, 10}, P{100, 50}}, P{65, 10}},            // collinear parallel x axis
+			{Tri{4, P{255, 210}, P{0, 60}, P{255, 60}}, P{185.615, 169.185}}, // collinear neg slope
+		}
+		for _, c := range cases {
+			assert.Truef(t, c.t.Contains(c.p), "triangle %d does not contain point", c.t.ID)
+		}
+	})
+}