add a wrapper for cascadio

docs/content/install.md

@@ -71,6 +71,8 @@ Trimesh has a lot of soft-required upstream packages, and we try to make sure th
 |`pyinstrument`| A sampling based profiler for performance tweaking. | | `test`|
 |`vhacdx`| A binding for VHACD which provides convex decompositions | | `recommend`|
 |`manifold3d`| A binding for the Manifold mesh boolean engine | | `recommend`|
+|`openctm`| A binding for OpenCTM loaders enabling `.ctm` loading | | `recommend`|
+|`cascadio`| A binding for OpenCASCADE enabling `.STEP` loading | | `recommend`|
 
 ## Adding A Dependency
 

pyproject.toml

@@ -5,7 +5,7 @@ requires = ["setuptools >= 61.0", "wheel"]
 [project]
 name = "trimesh"
 requires-python = ">=3.7"
-version = "4.1.8"
+version = "4.2.0"
 authors = [{name = "Michael Dawson-Haggerty", email = "mikedh@kerfed.com"}]
 license = {file = "LICENSE.md"}
 description = "Import, export, process, analyze and view triangular meshes."
@@ -88,8 +88,9 @@ recommend = [
     "pyglet<2",
     "psutil",
     "scikit-image",
-    "python-fcl",
-    "openctm",
+    "python-fcl", # do collision checks
+    "openctm", # load `CTM` compressed models
+    "cascadio", # load `STEP` files
     "manifold3d>=2.3.0"
 ]
 

tests/test_step.py

@@ -0,0 +1,21 @@
+try:
+    import generic as g
+except BaseException:
+    from . import generic as g
+
+
+class STEPTests(g.unittest.TestCase):
+    def test_basic(self):
+        try:
+            import cascadio  # noqa
+        except BaseException:
+            g.log.error("failed to get cascadio!", exc_info=True)
+            return
+
+        s = g.get_mesh("box_sides.STEP")
+        assert len(s.geometry) == 10
+
+
+if __name__ == "__main__":
+    g.trimesh.util.attach_to_log()
+    g.unittest.main()

trimesh/exchange/cascade.py

@@ -0,0 +1,72 @@
+import os
+import tempfile
+
+from ..typed import BinaryIO, Dict, Optional
+
+# used as an intermediate format
+from .gltf import load_glb
+
+
+def load_step(
+    file_obj: BinaryIO,
+    file_type,
+    tol_linear: Optional[float] = None,
+    tol_angular: Optional[float] = None,
+    tol_relative: Optional[bool] = False,
+    merge_primitives: bool = True,
+    **kwargs,
+) -> Dict:
+    """
+    Use `cascadio` a packaged version of OpenCASCADE
+    to load a STEP file using GLB as an intermediate.
+
+    Parameters
+    -----------
+    file_obj
+      STEP file to load.
+    **kwargs
+      Passed to `cascadio.step_to_glb`
+
+    Returns
+    ----------
+    kwargs
+      Keyword arguments for a Scene.
+    """
+    # TODO : update upstream `cascadio` to accept bytes objects
+    # so that we don't need to write a temporary file to disc!
+    with tempfile.TemporaryDirectory() as F:
+        # temporarily copy the STEP
+        stepfile = os.path.join(F, "data.step")
+        with open(stepfile, "wb") as f:
+            f.write(file_obj.read())
+
+        # where to save the converted GLB
+        glbfile = os.path.join(F, "converted.glb")
+
+        # the arguments for cascadio are not optional so
+        # filter out any `None` value arguments here
+        cascadio_kwargs = {
+            "merge_primitives": bool(merge_primitives),
+            "tol_linear": tol_linear,
+            "tol_angular": tol_angular,
+            "tol_relative": tol_relative,
+        }
+        # run the conversion
+        cascadio.step_to_glb(
+            stepfile,
+            glbfile,
+            **{k: v for k, v in cascadio_kwargs.items() if v is not None},
+        )
+
+        with open(glbfile, "rb") as f:
+            # return the parsed intermediate file
+            return load_glb(file_obj=f, merge_primitives=merge_primitives, **kwargs)
+
+
+try:
+    # wheels for most platforms: `pip install cascadio`
+    import cascadio
+
+    _cascade_loaders = {"stp": load_step, "step": load_step}
+except BaseException:
+    _cascade_loaders = {}

trimesh/exchange/load.py

@@ -13,6 +13,7 @@
 from ..util import log, now
 from . import misc
 from .binvox import _binvox_loaders
+from .cascade import _cascade_loaders
 from .dae import _collada_loaders
 from .gltf import _gltf_loaders
 from .misc import _misc_loaders
@@ -655,6 +656,7 @@ def _parse_file_args(
 mesh_loaders.update(_threedxml_loaders)
 mesh_loaders.update(_three_loaders)
 mesh_loaders.update(_xyz_loaders)
+mesh_loaders.update(_cascade_loaders)
 
 # collect loaders which return voxel types
 voxel_loaders = {}

trimesh/typed.py

@@ -1,5 +1,16 @@
 from pathlib import Path
-from typing import IO, Any, Dict, Iterable, List, Optional, Sequence, Tuple, Union
+from typing import (
+    IO,
+    Any,
+    BinaryIO,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    Union,
+)
 
 # our default integer and floating point types
 from numpy import float64, int64
@@ -22,6 +33,7 @@
     "Iterable",
     "Loadable",
     "IO",
+    "BinaryIO",
     "List",
     "Dict",
     "Any",