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fix after #6162 #623

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58b8bbc
Use buffer protocol to make Mat compatible with numpy
alxbilger Jun 19, 2026
3e9ce73
fix after #6162
alxbilger Jul 1, 2026
ce887fa
fix
alxbilger Jul 1, 2026
a0950e1
fix
alxbilger Jul 1, 2026
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Use buffer protocol to make Mat compatible with numpy
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@alxbilger
alxbilger committed Jun 19, 2026
commit 58b8bbcb28a6c28611ca24e679d7792096b720d0
38 changes: 32 additions & 6 deletions bindings/SofaTypes/src/SofaPython3/SofaTypes/Binding_Mat.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
#include "Binding_Mat.h"
#include <functional>
#include <pybind11/operators.h>
#include <pybind11/eigen.h>

#define BINDING_MAT_MAKE_NAME(R, C) \
std::string(std::string("Mat") + std::to_string(R) + "x" + std::to_string(C))
Expand Down Expand Up @@ -59,6 +60,31 @@ static void addMat(py::module & /*m*/, py::class_<Mat<R, C, double>> &p) {
typedef typename MatClass::Line Row;
p.def(py::init());
p.def(py::init<const MatClass &>());
p.def(py::init([](py::buffer b) {

/* Request a buffer descriptor from Python */
py::buffer_info info = b.request();

/* Some basic validation checks ... */
if (!info.item_type_is_equivalent_to<double>())
throw std::runtime_error(
"Incompatible format: expected a double array!");

if (info.ndim != 2)
throw std::runtime_error("Incompatible buffer dimension!");

return Mat<R, C, double>(static_cast<double*>(info.ptr));
}));
p.def_buffer([](Mat<R, C, double>& self) -> py::buffer_info {
return py::buffer_info(
self.elems.data(), // pointer
sizeof(double), // itemsize
py::format_descriptor<double>::format(), // format
2, // ndim
{static_cast<py::ssize_t>(R), static_cast<py::ssize_t>(C)}, // shape
{sizeof(double) * static_cast<py::ssize_t>(C), sizeof(double)} // strides (row-major)
);
});
p.def_property_readonly("rows", &MatClass::getNbLines);
p.def_property_readonly("cols", &MatClass::getNbCols);
p.def("clear", &MatClass::clear);
Expand Down Expand Up @@ -184,7 +210,7 @@ static void addMatProduct(py::module & /*m*/, py::class_<Mat<R_1, C_1, double>>
template <sofa::Size R, sofa::Size C> struct MATRIX {
static void addMat(py::module &m) {
typedef Mat<R, C, double> MatClass;
py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(R, C).c_str());
py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(R, C).c_str(), py::buffer_protocol());
::addMat(m, p);
}
};
Expand All @@ -203,7 +229,7 @@ template <> struct MATRIX<1, 1> {
// typedef typename MatClass::Line Row;
// typedef typename MatClass::Col Col;

py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(1, 1).c_str());
py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(1, 1).c_str(), py::buffer_protocol());
p.def(py::init([](py::list l) {
MatClass *mat = new MatClass(sofa::type::NOINIT);
if (py::isinstance<py::list>(l[0])) // 2D array
Expand Down Expand Up @@ -233,7 +259,7 @@ template <> struct MATRIX<2, 2> {
typedef typename MatClass::Line Row;
// typedef typename MatClass::Col Col;

py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(2, 2).c_str());
py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(2, 2).c_str(), py::buffer_protocol());
p.def(py::init<Row, Row>());
p.def(py::init([](py::list l) {
MatClass *mat = new MatClass(sofa::type::NOINIT);
Expand Down Expand Up @@ -264,7 +290,7 @@ template <> struct MATRIX<3, 3> {
typedef typename MatClass::Line Row;
// typedef typename MatClass::Col Col;

py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(3, 3).c_str());
py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(3, 3).c_str(), py::buffer_protocol());
p.def(py::init<Row, Row, Row>());
p.def(py::init([](py::list l) {
MatClass *mat = new MatClass(sofa::type::NOINIT);
Expand Down Expand Up @@ -295,7 +321,7 @@ template <> struct MATRIX<4, 4> {
typedef typename MatClass::Line Row;
// typedef typename MatClass::Col Col;

py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(4, 4).c_str());
py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(4, 4).c_str(), py::buffer_protocol());
p.def(py::init<Row, Row, Row, Row>());
p.def(py::init([](py::list l) {
MatClass *mat = new MatClass(sofa::type::NOINIT);
Expand Down Expand Up @@ -326,7 +352,7 @@ template <> struct MATRIX<3, 4> {
typedef typename MatClass::Line Row;
// typedef typename MatClass::Col Col;

py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(3, 4).c_str());
py::class_<MatClass> p(m, BINDING_MAT_MAKE_NAME(3, 4).c_str(), py::buffer_protocol());
p.def(py::init<Row, Row, Row>());
p.def(py::init([](py::list l) {
MatClass *mat = new MatClass(sofa::type::NOINIT);
Expand Down
22 changes: 22 additions & 0 deletions bindings/SofaTypes/tests/pyfiles/mat_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@
import Sofa
from SofaTypes import Mat1x1, Mat2x2, Mat3x3, Vec2d

import numpy as np

class TestMaterialMatrix(unittest.TestCase):

def test_Constructors(self):
Expand Down Expand Up @@ -62,3 +64,23 @@ def test_Operators(self):
m_test /= 2.0
expected_inplace_div = Mat2x2([[0.5, 1.0], [1.5, 2.0]])
self.assertEqual(m_test, expected_inplace_div)

def test_to_numpy(self):
m1 = Mat2x2([[1.0, 2.0], [3.0, 4.0]])
n1 = np.array(m1, copy = False) #n1 is a view on m1
n1[0, 0] = 9.0
self.assertEqual(m1[0][0], 9.0)

m2 = Mat2x2([[5.0, 6.0], [7.0, 8.0]])
n2 = np.array(m2, copy = False)

prod = n1 @ n2
expected_prod = np.array([[59.0, 70.0], [43.0, 50.0]])
np.testing.assert_array_equal(prod, expected_prod)

m3_prod = Mat2x2(prod)

self.assertEqual(m3_prod[0][0], prod[0,0])
self.assertEqual(m3_prod[0][1], prod[0,1])
self.assertEqual(m3_prod[1][0], prod[1,0])
self.assertEqual(m3_prod[1][1], prod[1,1])