Python binding for FMBScene

genmetaballs/src/cuda/bindings.cu

@@ -23,6 +23,8 @@ template <MemoryLocation location>
 void bind_image(nb::module_& m, const char* name);
 template <MemoryLocation location>
 void bind_image_view(nb::module_& m, const char* name);
+template <MemoryLocation location>
+void bind_fmb_scene(nb::module_& m, const char* name);
 
 NB_MODULE(_genmetaballs_bindings, m) {
 
@@ -66,6 +68,8 @@ NB_MODULE(_genmetaballs_bindings, m) {
              "apply the inverse covariance matrix to the given vector", nb::arg("vec"))
         .def("quadratic_form", &FMB::quadratic_form,
              "Evaluate the associated quadratic form at the given vector", nb::arg("vec"));
+    bind_fmb_scene<MemoryLocation::HOST>(fmb, "CPUFMBScene");
+    bind_fmb_scene<MemoryLocation::DEVICE>(fmb, "GPUFMBScene");
 
     /*
      * Geometry module bindings
@@ -244,3 +248,16 @@ void bind_image(nb::module_& m, const char* name) {
             return nb::str("{}(height={}, width={})").format(name, img.num_rows(), img.num_cols());
         });
 }
+
+template <MemoryLocation location>
+void bind_fmb_scene(nb::module_& m, const char* name) {
+    nb::class_<FMBScene<location>>(m, name)
+        .def(nb::init<size_t>(), nb::arg("size"))
+        .def_prop_ro("size", &FMBScene<location>::size)
+        .def("__len__", &FMBScene<location>::size)
+        .def("__getitem__", &FMBScene<location>::get_fmb, nb::arg("idx"),
+             "Get the (FMB, log_weight) tuple at index i")
+        .def("__repr__", [=](const FMBScene<location>& scene) {
+            return nb::str("{}(size={})").format(name, scene.size());
+        });
+}

genmetaballs/src/genmetaballs/core/__init__.py

@@ -10,6 +10,7 @@
     TwoParameterConfidence,
     ZeroParameterConfidence,
 )
+from genmetaballs._genmetaballs_bindings.fmb import CPUFMBScene, GPUFMBScene
 from genmetaballs._genmetaballs_bindings.image import CPUImage, GPUImage
 from genmetaballs._genmetaballs_bindings.utils import CPUFloatArray2D, GPUFloatArray2D, sigmoid
 
@@ -47,6 +48,21 @@ def make_image(height: int, width: int, device: DeviceType) -> CPUImage | GPUIma
         raise ValueError(f"Unsupported device type: {device}")
 
 
+def make_fmb_scene(size: int, device: DeviceType) -> CPUFMBScene | GPUFMBScene:
+    """Create an FMBScene on the specified device.
+
+    Args:
+        size: The number of FMBs in the scene.
+        device: 'cpu' or 'gpu' to specify the target device.
+    """
+    if device == "cpu":
+        return CPUFMBScene(size)
+    elif device == "gpu":
+        return GPUFMBScene(size)
+    else:
+        raise ValueError(f"Unsupported device type: {device}")
+
+
 __all__ = [
     "array2d_float",
     "ZeroParameterConfidence",
@@ -60,4 +76,5 @@ def make_image(height: int, width: int, device: DeviceType) -> CPUImage | GPUIma
     "FourParameterBlender",
     "ThreeParameterBlender",
     "make_image",
+    "make_fmb_scene",
 ]

tests/python_tests/test_fmb.py

@@ -3,7 +3,7 @@
 from scipy.spatial.distance import mahalanobis
 from scipy.spatial.transform import Rotation as Rot
 
-from genmetaballs.core import fmb, geometry
+from genmetaballs.core import fmb, geometry, make_fmb_scene
 
 FMB = fmb.FMB
 Pose, Vec3D, Rotation = geometry.Pose, geometry.Vec3D, geometry.Rotation
@@ -38,3 +38,13 @@ def test_fmb_quadratic_form(rng):
             FMB(pose, *extent).quadratic_form(Vec3D(*vec)),
             mahalanobis(vec, tran, np.linalg.inv(cov)) ** 2,
         )
+
+
+def test_fmb_scene_creation():
+    cpu_scene = make_fmb_scene(10, device="cpu")
+    assert isinstance(cpu_scene, fmb.CPUFMBScene)
+    assert len(cpu_scene) == 10
+
+    gpu_scene = make_fmb_scene(20, device="gpu")
+    assert isinstance(gpu_scene, fmb.GPUFMBScene)
+    assert len(gpu_scene) == 20