diff --git a/cpp/open3d/t/geometry/TriangleMesh.cpp b/cpp/open3d/t/geometry/TriangleMesh.cpp
index 05e8cc7b66f..11230c3ab7d 100644
--- a/cpp/open3d/t/geometry/TriangleMesh.cpp
+++ b/cpp/open3d/t/geometry/TriangleMesh.cpp
@@ -18,6 +18,7 @@
#include <Eigen/Core>
#include <string>
#include <unordered_map>
+#include <set>
#include "open3d/core/CUDAUtils.h"
#include "open3d/core/Device.h"
@@ -65,6 +66,54 @@ TriangleMesh::TriangleMesh(const core::Tensor &vertex_positions,
SetVertexPositions(vertex_positions);
SetTriangleIndices(triangle_indices);
}
+
+std::pair<core::Tensor, core::Tensor> TriangleMesh::ComputeAdjacencyList() {
+
+ if (IsEmpty()) {
+ utility::LogWarning("TriangleMesh is empty. No attributes computed!");
+ return std::make_pair(core::Tensor(), core::Tensor());
+ }
+
+ if(!HasTriangleIndices()) {
+ utility::LogWarning("TriangleMesh has no Indices. No attributes computed!");
+ return std::make_pair(core::Tensor(), core::Tensor());
+ }
+
+ core::Tensor tris_cpu =
+ GetTriangleIndices().To(core::Device()).Contiguous();
+
+ std::unordered_map< size_t, std::set<size_t> > adjacencyList;
+ auto insertEdge = [&adjacencyList](size_t s, size_t t){
+ adjacencyList[s].insert(t);
+ };
+
+ for(int idx = 0; idx < tris_cpu.GetLength(); idx++){
+ auto triangle_tensor = tris_cpu[idx];
+ auto *triangle = triangle_tensor.GetDataPtr<int>();
+ insertEdge(triangle[0], triangle[1]);
+ insertEdge(triangle[1], triangle[2]);
+ insertEdge(triangle[2], triangle[0]);
+ }
+
+ int num_vertices = GetVertexPositions().GetLength();
+ core::Tensor adjst = core::Tensor::Zeros({num_vertices+1}, core::Dtype::Int64);
+
+ int num_edges = tris_cpu.GetLength() * 3;
+ core::Tensor adjv = core::Tensor::Zeros({num_edges}, core::Dtype::Int64);
+
+ long prev_nnz = 0;
+ for(int idx = 1; idx <= num_vertices; idx++){
+ adjst[idx] = adjst[idx-1] + static_cast<long>(adjacencyList[idx-1].size());
+
+ int i = 0;
+ for(auto x : adjacencyList[idx-1]){
+ adjv[ prev_nnz + i] = x;
+ i++;
+ }
+ prev_nnz += static_cast<long>(adjacencyList[idx-1].size());
+ }
+ return std::make_pair(adjv, adjst);
+}
std::string TriangleMesh::ToString() const {
size_t num_vertices = 0;
diff --git a/cpp/open3d/t/geometry/TriangleMesh.h b/cpp/open3d/t/geometry/TriangleMesh.h
index 2b324751004..1bdbec48bde 100644
--- a/cpp/open3d/t/geometry/TriangleMesh.h
+++ b/cpp/open3d/t/geometry/TriangleMesh.h
@@ -828,6 +828,8 @@ class TriangleMesh : public Geometry, public DrawableGeometry {
TriangleMesh BooleanDifference(const TriangleMesh &mesh,
double tolerance = 1e-6) const;
+ std::pair<core::Tensor, core::Tensor> ComputeAdjacencyList();
+
/// Create an axis-aligned bounding box from vertex attribute "positions".
AxisAlignedBoundingBox GetAxisAlignedBoundingBox() const;
diff --git a/cpp/pybind/t/geometry/trianglemesh.cpp b/cpp/pybind/t/geometry/trianglemesh.cpp
index 3f56bb52d8b..9c891430c91 100644
--- a/cpp/pybind/t/geometry/trianglemesh.cpp
+++ b/cpp/pybind/t/geometry/trianglemesh.cpp
@@ -734,11 +734,14 @@ This function always uses the CPU device.
o3d.visualization.draw([{'name': 'difference', 'geometry': ans}])
)");
-
+ triangle_mesh.def("compute_adjacency_list", &TriangleMesh::ComputeAdjacencyList,
+ "Return Mesh Adjacency Matrix in CSR format using Triangle indices attribute.");
+
triangle_mesh.def("get_axis_aligned_bounding_box",
&TriangleMesh::GetAxisAlignedBoundingBox,
"Create an axis-aligned bounding box from vertex "
"attribute 'positions'.");
+
triangle_mesh.def("get_oriented_bounding_box",
&TriangleMesh::GetOrientedBoundingBox,
"Create an oriented bounding box from vertex attribute "
diff --git a/cpp/tests/t/geometry/TriangleMesh.cpp b/cpp/tests/t/geometry/TriangleMesh.cpp
index 7bca9b4a55e..e9e42e1aa18 100644
--- a/cpp/tests/t/geometry/TriangleMesh.cpp
+++ b/cpp/tests/t/geometry/TriangleMesh.cpp
@@ -25,6 +25,70 @@ INSTANTIATE_TEST_SUITE_P(TriangleMesh,
TriangleMeshPermuteDevices,
testing::ValuesIn(PermuteDevices::TestCases()));
+TEST_P(TriangleMeshPermuteDevices, ComputeAdjacencyList_emptyMesh) {
+//Test the interface and the case when mesh is empty
+
+ t::geometry::TriangleMesh empty_mesh;
+
+ auto listCSR = empty_mesh.ComputeAdjacencyList();
+
+ core::Tensor adjacent_vertex = listCSR.first;
+ core::Tensor adjacent_index_start = listCSR.second;
+ EXPECT_TRUE(adjacent_vertex.GetLength() == 0);
+ EXPECT_TRUE(adjacent_index_start.GetLength() == 0);
+}
+
+TEST_P(TriangleMeshPermuteDevices, ComputeAdjacencyList_matchValues) {
+//Test the actual values computed in the function
+
+ core::Device device = GetParam();
+ core::Dtype float_dtype_custom = core::Float64;
+ core::Dtype int_dtype_custom = core::Int32;
+
+ t::geometry::TriangleMesh mesh =
+ t::geometry::TriangleMesh::CreateTetrahedron(
+ 2, float_dtype_custom, int_dtype_custom, device);
+
+ auto listCSR = mesh.ComputeAdjacencyList();
+ core::Tensor adjv = listCSR.first;
+ core::Tensor adjst = listCSR.second;
+
+ EXPECT_TRUE( adjv.GetLength() > 0);
+ EXPECT_TRUE( adjst.GetLength() > 0);
+
+ core::Tensor csr_col = core::Tensor::Init<int64_t>(
+ {1, 2, 3, 0, 2, 3, 0, 1, 3, 0, 1, 2}, device);
+
+ core::Tensor csr_row_idx = core::Tensor::Init<int64_t>(
+ {0, 3, 6, 9, 12}, device);
+
+ EXPECT_EQ(adjv.GetLength(), csr_col.GetLength());
+ EXPECT_EQ(adjst.GetLength(), csr_row_idx.GetLength());
+ EXPECT_TRUE(adjv.AllEqual(csr_col));
+ EXPECT_TRUE(adjst.AllEqual(csr_row_idx));
+}
+
+TEST_P(TriangleMeshPermuteDevices, ComputeAdjacencyList_expectedBehaviour) {
+//On a larger mesh, test the interface and few expected properties
+
+ core::Device device = GetParam();
+ core::Dtype float_dtype_custom = core::Float64;
+ core::Dtype int_dtype_custom = core::Int32;
+
+ t::geometry::TriangleMesh mesh =
+ t::geometry::TriangleMesh::CreateIcosahedron(
+ 2, float_dtype_custom, int_dtype_custom, device);
+
+
+ auto listCSR = mesh.ComputeAdjacencyList();
+ core::Tensor adjv = listCSR.first;
+ core::Tensor adjst = listCSR.second;
+
+ EXPECT_TRUE( adjv.GetLength() > 0);
+ EXPECT_TRUE( adjst.GetLength() > 0);
+ EXPECT_EQ(adjst.ToFlatVector<int64_t>()[adjst.GetLength()-1], adjv.GetLength());
+}
+
TEST_P(TriangleMeshPermuteDevices, DefaultConstructor) {
t::geometry::TriangleMesh mesh;
diff --git a/python/test/t/geometry/test_trianglemesh.py b/python/test/t/geometry/test_trianglemesh.py
index 88678e3f877..d99072d6181 100644
--- a/python/test/t/geometry/test_trianglemesh.py
+++ b/python/test/t/geometry/test_trianglemesh.py
@@ -241,6 +241,66 @@ def test_create_octahedron(device):
assert octahedron_custom.vertex.positions.allclose(vertex_positions_custom)
assert octahedron_custom.triangle.indices.allclose(triangle_indices_custom)
+@pytest.mark.parametrize("device", list_devices())
+def test_compute_adjacency_list(device):
+ # Test with custom parameters.
+ mesh = o3d.t.geometry.TriangleMesh.create_icosahedron(
+ 2, o3c.float64, o3c.int32, device)
+ adjv, adjst = mesh.compute_adjacency_list()
+
+ # Check the number of edges at the end of row_index as per CRS format
+ assert adjst[-1] == len(adjv)
+
+ num_vertices = len(adjst)-1
+ # Create a adjacency matrix
+ adjacencyMatrix = np.zeros((num_vertices, num_vertices))
+
+ for s in range(num_vertices):
+ start = adjst[s].item()
+ end = adjst[s+1].item()
+ for v in range(start, end):
+ t = adjv[v].item()
+ adjacencyMatrix[s,t] = 1
+
+ # Number of edges
+ assert len(adjv) == adjacencyMatrix.sum()
+
+ # Adjacency Matrix should be symmetric
+ assert np.array_equal(adjacencyMatrix, adjacencyMatrix.T)
+
+ #Triangle faces from computed adjacency matrix should match
+ actual_indices = [
+ [0, 1, 4],
+ [0, 1, 5],
+ [0, 4, 8],
+ [0, 5, 11],
+ [0, 8, 11],
+ [1, 4, 9],
+ [1, 5, 10],
+ [1, 9, 10],
+ [2, 3, 6],
+ [2, 3, 7],
+ [2, 6, 10],
+ [2, 7, 9],
+ [2, 9, 10],
+ [3, 6, 11],
+ [3, 7, 8],
+ [3, 8, 11],
+ [4, 7, 8],
+ [4, 7, 9],
+ [5, 6, 10],
+ [5, 6, 11]
+ ]
+
+ computed_triangles = []
+ for i in range(num_vertices):
+ for j in range(i+1, num_vertices):
+ for k in range(j+1, num_vertices):
+ if (adjacencyMatrix[i,j] + adjacencyMatrix[j,k] + adjacencyMatrix[k,i] == 3):
+ computed_triangles.append([i,j,k])
+
+ assert len(computed_triangles) == len(actual_indices)
+ assert np.array_equal(np.array(actual_indices,int), np.array(computed_triangles,int))
@pytest.mark.parametrize("device", list_devices())
def test_create_icosahedron(device):