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comparison pkg/mesh/vertex.go @ 5703:d2ccf6bb6940 sr-v2

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Make plane eval for z-values of triangles numerial more robust.
author Sascha L. Teichmann <sascha.teichmann@intevation.de>
date Mon, 19 Feb 2024 17:48:13 +0100
parents 1222b777f51f
children 148abae1fcd0
comparison
equal deleted inserted replaced
5702:fe83406fe7ed 5703:d2ccf6bb6940
86 // the three points of the triangles are in. 86 // the three points of the triangles are in.
87 func (t *Triangle) Plane3D() Plane3D { 87 func (t *Triangle) Plane3D() Plane3D {
88 88
89 v0 := t[1].Sub(t[0]) 89 v0 := t[1].Sub(t[0])
90 v1 := t[2].Sub(t[0]) 90 v1 := t[2].Sub(t[0])
91 n := v0.Cross(v1).Normalize() 91 n := v0.Cross(v1)
92
93 // If the length of normal is near zero assume we have
94 // a plane constant in z with an average z value of
95 // the three vertices.
96 // This should protect us from the effects of collinear
97 // geometries.
98 l := n.Length()
99 if l < 1e-7 {
100 sum := t[0].Z + t[1].Z + t[2].Z
101 return Plane3D{
102 A: 0,
103 B: 0,
104 C: 1,
105 D: -sum / 3,
106 }
107 }
108 n = n.Scale(1 / l)
92 109
93 // x*nx+ y*ny+ z*nz + d = 0 110 // x*nx+ y*ny+ z*nz + d = 0
94 // d = - (x*nx+ y*ny + z*nz) 111 // d = - (x*nx+ y*ny + z*nz)
95 d := -t[0].Dot(n) 112 d := -t[0].Dot(n)
96 return Plane3D{ 113 return Plane3D{