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annotate pkg/mesh/meshserialize_v2.go @ 5686:c33a5354328d sr-v2

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Add stubs for de/serialize v2 meshes.
author Sascha L. Teichmann <sascha.teichmann@intevation.de>
date Mon, 12 Feb 2024 01:17:22 +0100
parents 0ee8ace01b60
children 8ff842858434
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rev   line source
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1 // This is Free Software under GNU Affero General Public License v >= 3.0
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2 // without warranty, see README.md and license for details.
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3 //
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4 // SPDX-License-Identifier: AGPL-3.0-or-later
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5 // License-Filename: LICENSES/AGPL-3.0.txt
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6 //
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7 // Copyright (C) 2024 by via donau
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8 // – Österreichische Wasserstraßen-Gesellschaft mbH
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9 // Software engineering by Intevation GmbH
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10 //
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11 // Author(s):
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12 // * Sascha L. Teichmann <sascha.teichmann@intevation.de>
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13
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14 package mesh
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15
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16 import (
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17 "bufio"
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18 "cmp"
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19 "errors"
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20 "io"
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21 "math"
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22 "slices"
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23 "sort"
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24 )
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25
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26 func (s *STRTree) serializeV2(w io.Writer) error {
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27 // TODO: implement me!
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28 return errors.New("not implemented, yet")
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29 }
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30
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31 func (s *STRTree) deserializeV2(r *bufio.Reader) error {
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32 // TODO: implement me!
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33 return errors.New("not implemented, yet")
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34 }
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35
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36 // optimizeForSerializationV2 prepares the mesh to be stored in V2.
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37 func (s *STRTree) optimizeForSerializationV2() {
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38 s.removeUnusedTriangles()
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39 s.sortVertices()
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40 s.sortIndices()
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41 }
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42
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43 // removeUnusedTriangles removes all triangles from the
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44 // TIN that are not registered in the spatial index.
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45 func (s *STRTree) removeUnusedTriangles() {
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46 used := make([]bool, len(s.tin.Triangles))
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47 unused := len(used)
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48 s.allTriangleIndices(func(indices []int32) {
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49 for _, idx := range indices {
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50 used[idx] = true
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51 unused-- // They only occur once in the spatial index.
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52 }
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53 })
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54 if unused <= 0 {
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55 return
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56 }
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57 newTris := make([][]int32, 0, len(s.tin.Triangles)-unused)
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58 remap := map[int32]int32{}
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59 for idx, tri := range s.tin.Triangles {
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60 if used[idx] {
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61 remap[int32(idx)] = int32(len(newTris))
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62 newTris = append(newTris, tri)
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63 }
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64 }
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65 s.tin.Triangles = newTris
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66 // Update the spatial index as the gaps are now closed.
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67 s.allTriangleIndices(func(indices []int32) {
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68 for i, idx := range indices {
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69 indices[i] = remap[idx]
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70 }
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71 })
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72 }
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73
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74 // sortVertices so that the deltas between neighbors are minimized.
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75 func (s *STRTree) sortVertices() {
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76 vertices := s.tin.Vertices
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77 indices := make([]int32, len(vertices))
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78 for i := range len(indices) {
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79 indices[i] = int32(i)
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80 }
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81
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82 // Take aspect ratio of bbox into account.
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83 width := s.tin.Max.X - s.tin.Min.X
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84 height := s.tin.Max.Y - s.tin.Min.Y
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85 if width == 0 || height == 0 {
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86 return
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87 }
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88
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89 // v = len(vertices)
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90 // r = max(w, h)/min(w, h)
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91 // n * t = v <=> n = v/t
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92 // n / t = r <=> n = r*t
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93 // v/t = r*t
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94 // v = r*t^2
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95 // v/r = t^2
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96 // t = sqrt(v/r)
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97 r := float64(max(width, height)) / float64(min(width, height))
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98 t := int(math.Ceil(math.Sqrt(float64(len(vertices)) / r)))
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99
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100 var d1, d2 func(int32, int32) int
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101
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102 if width > height {
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103 // Sort in X first and slices alternating up and down
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104 slices.SortFunc(indices, func(a, b int32) int {
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105 return cmp.Compare(vertices[a].X, vertices[b].X)
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106 })
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107 d1 = func(a, b int32) int { return cmp.Compare(vertices[a].Y, vertices[b].Y) }
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108 d2 = func(a, b int32) int { return cmp.Compare(vertices[b].Y, vertices[a].Y) }
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109 } else {
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110 // Sort in Y first and slices alternating left and right
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111 slices.SortFunc(indices, func(a, b int32) int {
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112 return cmp.Compare(vertices[a].Y, vertices[b].Y)
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113 })
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114 d1 = func(a, b int32) int { return cmp.Compare(vertices[a].X, vertices[b].X) }
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115 d2 = func(a, b int32) int { return cmp.Compare(vertices[b].X, vertices[a].X) }
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116 }
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117
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118 for p := indices; len(p) > 0; d1, d2 = d2, d1 {
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119 l := min(len(p), t)
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120 slices.SortStableFunc(p[:l], d2)
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121 p = p[l:]
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122 }
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123
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124 // We really need to to sort the vertices actually, too.
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125 sort.Slice(vertices, func(i, j int) bool { return indices[i] < indices[j] })
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126
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127 reindices := make([]int32, len(indices))
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128 for i, idx := range indices {
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129 reindices[idx] = int32(i)
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130 }
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131
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132 // Update the indices in the triangles.
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133 for _, tri := range s.tin.Triangles {
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134 for i, idx := range tri {
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135 tri[i] = reindices[idx]
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136 }
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137 }
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138 }