godot/thirdparty/thekla_atlas/nvmesh/param/OrthogonalProjectionMap.cpp

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// This code is in the public domain -- castano@gmail.com
#include "nvmesh.h" // pch
#include "OrthogonalProjectionMap.h"
#include "nvcore/Array.inl"
#include "nvmath/Fitting.h"
#include "nvmath/Vector.inl"
#include "nvmath/Box.inl"
#include "nvmath/Plane.inl"
#include "nvmesh/halfedge/Mesh.h"
#include "nvmesh/halfedge/Vertex.h"
#include "nvmesh/halfedge/Face.h"
#include "nvmesh/geometry/Bounds.h"
using namespace nv;
bool nv::computeOrthogonalProjectionMap(HalfEdge::Mesh * mesh)
{
Vector3 axis[2];
#if 1
uint vertexCount = mesh->vertexCount();
Array<Vector3> points(vertexCount);
points.resize(vertexCount);
for (uint i = 0; i < vertexCount; i++)
{
points[i] = mesh->vertexAt(i)->pos;
}
#if 0
axis[0] = Fit::computePrincipalComponent_EigenSolver(vertexCount, points.buffer());
axis[0] = normalize(axis[0]);
Plane plane = Fit::bestPlane(vertexCount, points.buffer());
Vector3 n = plane.vector();
axis[1] = cross(axis[0], n);
axis[1] = normalize(axis[1]);
#else
// Avoid redundant computations.
float matrix[6];
Fit::computeCovariance(vertexCount, points.buffer(), matrix);
if (matrix[0] == 0 && matrix[3] == 0 && matrix[5] == 0) {
return false;
}
float eigenValues[3];
Vector3 eigenVectors[3];
if (!nv::Fit::eigenSolveSymmetric3(matrix, eigenValues, eigenVectors)) {
return false;
}
axis[0] = normalize(eigenVectors[0]);
axis[1] = normalize(eigenVectors[1]);
#endif
#else
// IC: I thought this was generally more robust, but turns out it's not even guaranteed to return a valid projection. Imagine a narrow quad perpendicular to one plane, but rotated so that the shortest axis of
// the bounding box is in the direction of that plane.
// Use the shortest box axis
Box box = MeshBounds::box(mesh);
Vector3 dir = box.extents();
if (fabs(dir.x) <= fabs(dir.y) && fabs(dir.x) <= fabs(dir.z)) {
axis[0] = Vector3(0, 1, 0);
axis[1] = Vector3(0, 0, 1);
}
else if (fabs(dir.y) <= fabs(dir.z)) {
axis[0] = Vector3(1, 0, 0);
axis[1] = Vector3(0, 0, 1);
}
else {
axis[0] = Vector3(1, 0, 0);
axis[1] = Vector3(0, 1, 0);
}
#endif
// Project vertices to plane.
for (HalfEdge::Mesh::VertexIterator it(mesh->vertices()); !it.isDone(); it.advance())
{
HalfEdge::Vertex * vertex = it.current();
vertex->tex.x = dot(axis[0], vertex->pos);
vertex->tex.y = dot(axis[1], vertex->pos);
}
return true;
}