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merged 4 commits into from
Sep 15, 2025
Merged

Better Cylinder Model Sampling #6342

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343776c
Add cylinder sampling test with intersecting lines
akretz Sep 12, 2025
6817084
Compute axis direction using cross product
akretz Sep 12, 2025
027d75c
Add symmetry cylinder sampling test
akretz Sep 12, 2025
7a1a2b5
Estimate cylinder radius using both points
akretz Sep 12, 2025
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13 changes: 6 additions & 7 deletions sample_consensus/include/pcl/sample_consensus/impl/sac_model_cylinder.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -94,29 +94,26 @@ pcl::SampleConsensusModelCylinder<PointT, PointNT>::computeModelCoefficients (
Eigen::Vector4f n1 ((*normals_)[samples[0]].normal[0], (*normals_)[samples[0]].normal[1], (*normals_)[samples[0]].normal[2], 0.0f);
Eigen::Vector4f n2 ((*normals_)[samples[1]].normal[0], (*normals_)[samples[1]].normal[1], (*normals_)[samples[1]].normal[2], 0.0f);
Eigen::Vector4f w = n1 + p1 - p2;
Eigen::Vector4f line_dir = n1.cross3 (n2);

float a = n1.dot (n1);
float b = n1.dot (n2);
float c = n2.dot (n2);
float d = n1.dot (w);
float e = n2.dot (w);
float denominator = a*c - b*b;
float sc, tc;
float denominator = line_dir.squaredNorm ();
float sc;
// Compute the line parameters of the two closest points
if (denominator < 1e-8) // The lines are almost parallel
{
sc = 0.0f;
tc = (b > c ? d / b : e / c); // Use the largest denominator
}
else
{
sc = (b*e - c*d) / denominator;
tc = (a*e - b*d) / denominator;
}

// point_on_axis, axis_direction
Eigen::Vector4f line_pt = p1 + n1 + sc * n1;
Eigen::Vector4f line_dir = p2 + tc * n2 - line_pt;
line_dir.normalize ();

model_coefficients.resize (model_size_);
Expand All @@ -129,7 +126,9 @@ pcl::SampleConsensusModelCylinder<PointT, PointNT>::computeModelCoefficients (
model_coefficients[4] = line_dir[1];
model_coefficients[5] = line_dir[2];
// cylinder radius
model_coefficients[6] = static_cast<float> (sqrt (pcl::sqrPointToLineDistance (p1, line_pt, line_dir)));
model_coefficients[6] = static_cast<float> (
0.5 * (sqrt (pcl::sqrPointToLineDistance (p1, line_pt, line_dir)) +
sqrt (pcl::sqrPointToLineDistance (p2, line_pt, line_dir))));

if (model_coefficients[6] > radius_max_ || model_coefficients[6] < radius_min_)
return (false);
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60 changes: 60 additions & 0 deletions test/sample_consensus/test_sample_consensus_quadric_models.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1641,6 +1641,66 @@ TEST(SampleConsensusModelTorusSelfIntersectSpindle, RANSAC)
EXPECT_NEAR(coeff[7], 0.25000000000000017, 1e-2);
}

TEST(SampleConsensusModelCylinder, SampleIntersectingLines)
{
PointCloud<PointXYZ> cloud;
PointCloud<Normal> normals;
cloud.resize(2);
normals.resize(2);
cloud[0].getVector3fMap() << 0.0f, 1.0f, 0.0f;
cloud[1].getVector3fMap() << 1.0f, 0.0f, 0.0f;
normals[0].getNormalVector3fMap() << 0.0f, 1.0f, 0.0f;
normals[1].getNormalVector3fMap() << 1.0f, 0.0f, 0.0f;

SampleConsensusModelCylinder<PointXYZ, Normal> model(cloud.makeShared());
model.setInputNormals(normals.makeShared());

Eigen::VectorXf model_coefficients;
model.computeModelCoefficients({0, 1}, model_coefficients);

ASSERT_EQ(7, model_coefficients.size());

EXPECT_NEAR(0.0f, model_coefficients[0], 1e-5f);
EXPECT_NEAR(0.0f, model_coefficients[1], 1e-5f);
EXPECT_NEAR(0.0f, model_coefficients[3], 1e-5f);
EXPECT_NEAR(0.0f, model_coefficients[4], 1e-5f);
EXPECT_LT(0.0f, std::abs(model_coefficients[5]));
EXPECT_NEAR(1.0f, model_coefficients[6], 1e-5f);
}

TEST(SampleConsensusModelCylinder, SampleModelsSymmetric)
{
PointCloud<PointXYZ> cloud;
PointCloud<Normal> normals;
cloud.resize(2);
normals.resize(2);
cloud[0].getVector3fMap() << 0.1f, 1.3f, 0.4f;
cloud[1].getVector3fMap() << 1.2f, -0.2f, -0.1f;
normals[0].getNormalVector3fMap() << 0.0f, 0.9f, -0.1f;
normals[1].getNormalVector3fMap() << 1.1f, -0.2f, 0.0f;

SampleConsensusModelCylinder<PointXYZ, Normal> model(cloud.makeShared());
model.setInputNormals(normals.makeShared());

Eigen::VectorXf model_coefficients, model_coefficients_swapped;
model.computeModelCoefficients({0, 1}, model_coefficients);
model.computeModelCoefficients({1, 0}, model_coefficients_swapped);

ASSERT_EQ(7, model_coefficients.size());
ASSERT_EQ(7, model_coefficients_swapped.size());

Eigen::Vector4f pt1(model_coefficients[0], model_coefficients[1], model_coefficients[2], 0.f);
Eigen::Vector4f dir1(model_coefficients[3], model_coefficients[4], model_coefficients[5], 0.f);
Eigen::Vector4f pt2(model_coefficients_swapped[0], model_coefficients_swapped[1], model_coefficients_swapped[2], 0.f);
Eigen::Vector4f dir2(model_coefficients_swapped[3], model_coefficients_swapped[4], model_coefficients_swapped[5], 0.f);

// Check if both cylinder axes are the same
EXPECT_GT(1e-5, sqrPointToLineDistance(pt2, pt1, dir1));
EXPECT_GT(1e-5f, (dir1 * (dir2.x() / dir1.x()) - dir2).squaredNorm());

EXPECT_NEAR(model_coefficients[6], model_coefficients_swapped[6], 1e-5f);
}

int
main(int argc, char** argv)
{
Expand Down