Mercurial > gemma
view pkg/mesh/triangulation.go @ 5718:3d497077f888 uploadwg
Implemented direct file upload as alternative import method for WG.
For testing and data corrections it is useful to be able to import
waterway gauges data directly by uploading a xml file.
author | Sascha Wilde <wilde@sha-bang.de> |
---|---|
date | Thu, 18 Apr 2024 19:23:19 +0200 |
parents | 1222b777f51f |
children |
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// Copyright (C) 2018 Michael Fogleman // // Permission is hereby granted, free of charge, to any person obtaining // a copy of this software and associated documentation files (the "Software"), // to deal in the Software without restriction, including without limitation // the rights to use, copy, modify, merge, publish, distribute, sublicense, // and/or sell copies of the Software, and to permit persons to whom the // Software is furnished to do so, subject to the following conditions: // // The above copyright notice and this permission notice shall be included // in all copies or substantial portions of the Software. // // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL // THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. package mesh import ( "math" "gemma.intevation.de/gemma/pkg/log" "gonum.org/v1/gonum/stat" ) // Triangulation represents a triangulation // consisting of its vertices, the convex hull, // the triangles and a half edge representation. type Triangulation struct { Points []Vertex ConvexHull []Vertex Triangles []int32 Halfedges []int32 } // Triangulate returns a Delaunay triangulation of the provided points. func Triangulate(points []Vertex) (*Triangulation, error) { t := newTriangulator(points) err := t.triangulate() return &Triangulation{points, t.convexHull(), t.triangles, t.halfedges}, err } // EstimateTooLong estimates an edge length which is too long // to be a real triangle in the triangulation. // It is assumed that the triangles in this mesh are // more or less equally sized. If an edge length is more // than the 3.5 of the standard dev of the medium length // it is considered as too long. func (t *Triangulation) EstimateTooLong() float64 { num := len(t.Triangles) / 3 lengths := make([]float64, 0, num) points := t.Points tris: for i := 0; i < num; i++ { idx := i * 3 var max float64 vs := t.Triangles[idx : idx+3] for j, vj := range vs { if t.Halfedges[idx+j] < 0 { continue tris } k := (j + 1) % 3 if l := points[vj].Distance2D(points[vs[k]]); l > max { max = l } } lengths = append(lengths, max) } std := stat.StdDev(lengths, nil) return 3.5 * std } // ConcaveHull constructs a concave hull for this mesh, // Triangles that are considered as too large based on // the EstimateTooLong estimation are removed from the border. func (t *Triangulation) ConcaveHull(tooLong float64) (LineStringZ, map[int32]struct{}) { if tooLong <= 0 { tooLong = t.EstimateTooLong() } tooLong *= tooLong var candidates []int32 points := t.Points for i, num := 0, len(t.Triangles)/3; i < num; i++ { idx := i * 3 var max float64 vs := t.Triangles[idx : idx+3] for j, vj := range vs { k := (j + 1) % 3 if l := points[vj].SquaredDistance2D(points[vs[k]]); l > max { max = l } } if max > tooLong { candidates = append(candidates, int32(i)) } } removed := map[int32]struct{}{} isBorder := func(n int32) bool { n *= 3 for i := int32(0); i < 3; i++ { e := n + i o := t.Halfedges[e] if o < 0 { return true } if _, found := removed[o/3]; found { return true } } return false } var newCandidates []int32 log.Infof("candidates: %d\n", len(candidates)) for len(candidates) > 0 { oldRemoved := len(removed) for _, i := range candidates { if isBorder(i) { removed[i] = struct{}{} } else { newCandidates = append(newCandidates, i) } } if oldRemoved == len(removed) { break } candidates = newCandidates newCandidates = newCandidates[:0] } log.Infof("candidates left: %d\n", len(candidates)) log.Infof("triangles: %d\n", len(t.Triangles)/3) log.Infof("info: triangles to remove: %d\n", len(removed)) type edge struct { a, b int32 prev, next *edge } isClosed := func(e *edge) bool { for curr := e.next; curr != nil; curr = curr.next { if curr == e { return true } } return false } open := map[int32]*edge{} var rings []*edge for i, num := int32(0), int32(len(t.Triangles)/3); i < num; i++ { if _, found := removed[i]; found { continue } n := i * 3 for j := int32(0); j < 3; j++ { e := n + j f := t.Halfedges[e] if f >= 0 { if _, found := removed[f/3]; !found { continue } } a := t.Triangles[e] b := t.Triangles[n+(j+1)%3] curr := &edge{a: a, b: b} if old := open[a]; old != nil { delete(open, a) if old.a == a { old.prev = curr curr.next = old } else { old.next = curr curr.prev = old } if isClosed(old) { rings = append(rings, old) } } else { open[a] = curr } if old := open[b]; old != nil { delete(open, b) if old.b == b { old.next = curr curr.prev = old } else { old.prev = curr curr.next = old } if isClosed(old) { rings = append(rings, old) } } else { open[b] = curr } } } if len(open) > 0 { log.Warnf("open vertices left: %d\n", len(open)) } if len(rings) == 0 { log.Warnln("no ring found") return nil, removed } curr := rings[0] polygon := LineStringZ{ points[curr.a], points[curr.b], } for curr = curr.next; curr != rings[0]; curr = curr.next { polygon = append(polygon, points[curr.b]) } polygon = append(polygon, t.Points[rings[0].a]) log.Infof("length of boundary: %d\n", len(polygon)) return polygon, removed } // TriangleSlices returns the indices of the triangles // of the mesh as slices og length three. func (t *Triangulation) TriangleSlices() [][]int32 { sl := make([][]int32, len(t.Triangles)/3) var j int for i := range sl { sl[i] = t.Triangles[j : j+3] j += 3 } return sl } // Tin creates a TIN out of this triangulation. func (t *Triangulation) Tin() *Tin { min := Vertex{math.MaxFloat64, math.MaxFloat64, math.MaxFloat64} max := Vertex{-math.MaxFloat64, -math.MaxFloat64, -math.MaxFloat64} vertices := t.Points for _, v := range vertices { min.Minimize(v) max.Maximize(v) } return &Tin{ Vertices: vertices, Triangles: t.TriangleSlices(), Min: min, Max: max, } }