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Pad using weighted vertex normals #238

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merged 6 commits into from
May 6, 2024
Merged

Pad using weighted vertex normals #238

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59559bc
compute weighted vertex normals
kbrameld Apr 2, 2024
e5b1630
pad using vertex normals
kbrameld Apr 2, 2024
58bf9d2
format
kbrameld Apr 3, 2024
05f89da
use eigen map
kbrameld Apr 3, 2024
e6eb2bb
replace computeVertexNormals
kbrameld Apr 3, 2024
e7dd358
use Eigen Map to simplify calculations
kbrameld Apr 4, 2024
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78 changes: 40 additions & 38 deletions src/shapes.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -562,7 +562,8 @@ void Mesh::computeWeightedVertexNormals()
computeTriangleNormals();
if (vertex_count && !vertex_normals)
vertex_normals = new double[vertex_count * 3];
EigenSTL::vector_Vector3d avg_normals(vertex_count, Eigen::Vector3d(0, 0, 0));
Eigen::Map<Eigen::Matrix<double, 3, Eigen::Dynamic>> mapped_normals(vertex_normals, 3, vertex_count);
mapped_normals.setZero();

for (unsigned int tIdx = 0; tIdx < triangle_count; ++tIdx)
{
Expand All @@ -575,48 +576,49 @@ void Mesh::computeWeightedVertexNormals()
unsigned int v3 = triangles[tIdx3_2];

// Get angles for each vertex at this triangle
Eigen::Vector3d p1{ vertices[3 * v1], vertices[3 * v1 + 1], vertices[3 * v1 + 2] };
Eigen::Vector3d p2{ vertices[3 * v2], vertices[3 * v2 + 1], vertices[3 * v2 + 2] };
Eigen::Vector3d p3{ vertices[3 * v3], vertices[3 * v3 + 1], vertices[3 * v3 + 2] };

{
// Use re-arranged dot product equation to calculate angle between two vectors
auto angleBetweenVectors = [](const Eigen::Vector3d& v1, const Eigen::Vector3d& v2) -> double {
return std::acos(v1.dot(v2) / (v1.norm() * v2.norm()));
};

// Use law of cosines to compute angles
auto ang1 = angleBetweenVectors(p2 - p1, p3 - p1);
auto ang2 = angleBetweenVectors(p1 - p2, p3 - p2);
auto ang3 = angleBetweenVectors(p1 - p3, p2 - p3);

// Weight normal with angle
avg_normals[v1][0] += triangle_normals[tIdx3] * ang1;
avg_normals[v1][1] += triangle_normals[tIdx3_1] * ang1;
avg_normals[v1][2] += triangle_normals[tIdx3_2] * ang1;

avg_normals[v2][0] += triangle_normals[tIdx3] * ang2;
avg_normals[v2][1] += triangle_normals[tIdx3_1] * ang2;
avg_normals[v2][2] += triangle_normals[tIdx3_2] * ang2;

avg_normals[v3][0] += triangle_normals[tIdx3] * ang3;
avg_normals[v3][1] += triangle_normals[tIdx3_1] * ang3;
avg_normals[v3][2] += triangle_normals[tIdx3_2] * ang3;
}
Eigen::Map<Eigen::Vector3d> p1{ vertices + 3 * v1, 3 };
Eigen::Map<Eigen::Vector3d> p2{ vertices + 3 * v2, 3 };
Eigen::Map<Eigen::Vector3d> p3{ vertices + 3 * v3, 3 };

// Use re-arranged dot product equation to calculate angle between two vectors
auto angleBetweenVectors = [](const Eigen::Vector3d& vec1, const Eigen::Vector3d& vec2) -> double {
double vec1_norm = vec1.norm();
double vec2_norm = vec2.norm();

// Handle the case where either vector has zero length, to prevent division-by-zero
if (vec1_norm == 0.0 || vec2_norm == 0.0)
return 0.0;

return std::acos(vec1.dot(vec2) / (vec1_norm * vec2_norm));
};

// Use law of cosines to compute angles
auto ang1 = angleBetweenVectors(p2 - p1, p3 - p1);
auto ang2 = angleBetweenVectors(p1 - p2, p3 - p2);
auto ang3 = angleBetweenVectors(p1 - p3, p2 - p3);

// Weight normal with angle
mapped_normals.col(v1)[0] += triangle_normals[tIdx3] * ang1;
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mapped_normals.col(v1)[1] += triangle_normals[tIdx3_1] * ang1;
mapped_normals.col(v1)[2] += triangle_normals[tIdx3_2] * ang1;

mapped_normals.col(v2)[0] += triangle_normals[tIdx3] * ang2;
mapped_normals.col(v2)[1] += triangle_normals[tIdx3_1] * ang2;
mapped_normals.col(v2)[2] += triangle_normals[tIdx3_2] * ang2;

mapped_normals.col(v3)[0] += triangle_normals[tIdx3] * ang3;
mapped_normals.col(v3)[1] += triangle_normals[tIdx3_1] * ang3;
mapped_normals.col(v3)[2] += triangle_normals[tIdx3_2] * ang3;
}

for (std::size_t i = 0; i < avg_normals.size(); ++i)
// Normalize each column of the matrix
for (int i = 0; i < mapped_normals.cols(); ++i)
{
auto& avg_normal = avg_normals[i];
if (avg_normal.squaredNorm() != 0.0)
auto mapped_normal = mapped_normals.col(i);
if (mapped_normal.squaredNorm() != 0.0)
{
avg_normal.normalize();
mapped_normal.normalize();
}

unsigned int i3 = i * 3;
vertex_normals[i3] = avg_normal[0];
vertex_normals[i3 + 1] = avg_normal[1];
vertex_normals[i3 + 2] = avg_normal[2];
}
}

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