fix exception when plotting a model with any line bodies

Author: Mohamed Koubaa

src/ansys/mechanical/core/embedding/viz/pyvista_plotter.py

@@ -44,7 +44,7 @@ def _transform_to_pyvista(transform: "Ansys.ACT.Math.Matrix4D"):
     return np_transform
 
 
-def _get_nodes_and_coords(tri_tessellation: "Ansys.Mechanical.Scenegraph.TriTessellationNode"):
+def _get_tri_nodes_and_coords(tri_tessellation: "Ansys.Mechanical.Scenegraph.TriTessellationNode"):
     """Get the nodes and indices of the TriTessellationNode.
 
     pyvista format expects a number of vertices per facet which is always 3
@@ -55,6 +55,19 @@ def _get_nodes_and_coords(tri_tessellation: "Ansys.Mechanical.Scenegraph.TriTess
     return np_coordinates, np_indices
 
 
+def _get_nodes_and_coords(node: "Ansys.Mechanical.Scenegraph.Node"):
+    """Get the nodes and indices of the Scenegraph node.
+
+    Currently only supported for tri tessellation nodes
+    """
+    if isinstance(node, Ansys.Mechanical.Scenegraph.TriTessellationNode):
+        return _get_tri_nodes_and_coords(node)
+
+    # TODO - support line tessellation node. See issue #809
+    #if isinstance(node, Ansys.Mechanical.Scenegraph.LineTessellationNode):
+    return None, None
+
+
 def to_pyvista_plotter(app: "ansys.mechanical.core.embedding.App"):
     """Convert the app's geometry to a pyvista plotter instance."""
     plotter = pv.Plotter()
@@ -63,6 +76,8 @@ def to_pyvista_plotter(app: "ansys.mechanical.core.embedding.App"):
     ):
         scenegraph_node = Ansys.ACT.Mechanical.Tools.ScenegraphHelpers.GetScenegraph(body)
         np_coordinates, np_indices = _get_nodes_and_coords(scenegraph_node.Child)
+        if np_coordinates is None or np_indices is None:
+            continue
         pv_transform = _transform_to_pyvista(scenegraph_node.Transform)
         polydata = pv.PolyData(np_coordinates, np_indices).transform(pv_transform)
         color = pv.Color(bgr_to_rgb_tuple(body.Color))

src/ansys/mechanical/core/embedding/viz/usd_converter.py

@@ -73,22 +73,34 @@ def _convert_tri_tessellation_node(
     return mesh_prim
 
 
-def _convert_transform_node(
-    node: "Ansys.Mechanical.Scenegraph.TransformNode",
+def _create_prim_with_transform(
     stage: Usd.Stage,
     path: str,
-    rgb: typing.Tuple[int, int, int],
+    node: "Ansys.Mechanical.Scenegraph.TransformNode"
 ) -> Usd.Prim:
-    """Convert a mechanical transform node into a Usd Xform prim."""
+    """Create an empty Usd Xform prim based on a mechanical transform node."""
     prim = UsdGeom.Xform.Define(stage, path)
     rotation, translation = _transform_to_rotation_translation(node.Transform)
     prim.AddOrientOp().Set(rotation)
     prim.AddTranslateOp().Set(translation)
+    return prim
+
+
+def _convert_transform_node(
+    node: "Ansys.Mechanical.Scenegraph.TransformNode",
+    stage: Usd.Stage,
+    path: str,
+    rgb: typing.Tuple[int, int, int],
+) -> None:
+    """Add a Usd prim to the stage based on the given mechanical transform node.
+
+    Currently only supports transforms that contain a single tri tessellation node.
+    """
     child_node = node.Child
-    child_path = prim.GetPath().AppendPath("TriTessellation")
     if isinstance(child_node, Ansys.Mechanical.Scenegraph.TriTessellationNode):
+        prim = _create_prim_with_transform(stage, path, node)
+        child_path = prim.GetPath().AppendPath("TriTessellation")
         _convert_tri_tessellation_node(child_node, stage, child_path, rgb)
-    return prim
 
 
 def to_usd_stage(app: "ansys.mechanical.core.embedding.App", name: str) -> None: