Handle non-surface Collada geometry

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 * `Joint._create` no longer rotates `current_axis` once more every time it runs. It transformed the axis in place instead of recomputing it from `axis`, so re-initializing the transformation tree of a model that has joints (e.g. after its structure changed) left the joint axes wrong — 90 degrees out per extra call for a joint whose origin is rotated by 90 degrees. Models built or loaded in one pass were unaffected, which is why this went unnoticed.
+* The COLLADA mesh importer now skips empty and non-surface geometry instead of aborting files that otherwise contain valid meshes, and reads colors from Lambert, Blinn, and constant shaders in addition to Phong.
 
 ### Removed
 

src/compas_robots/resources/mesh_importer.py

@@ -95,15 +95,18 @@ def tag(name):
                 M = M[0:4], M[4:8], M[8:12], M[12:16]
                 transform = Transformation.from_matrix(M)
 
-        # primitive elements can be any combination of:
-        # lines, linestrips, polygons, polylist, triangles, trifans, tristrips
-        # The current implementation only supports triangles and polylist of triangular meshes
+        # Primitive elements can be any combination of:
+        # lines, linestrips, polygons, polylist, triangles, trifans, tristrips.
+        # The current implementation only supports triangles and polylist surface meshes.
+        # Other primitives and empty geometry nodes are ignored because this importer returns
+        # face-based Mesh objects. Raise only if the complete file has no supported surfaces.
         primitive_element_sets = []
         primitive_element_sets.extend(mesh_xml.findall(tag("triangles")))
         primitive_element_sets.extend(mesh_xml.findall(tag("polylist")))
 
         if len(primitive_element_sets) == 0:
-            raise Exception("No primitive elements found (currently only triangles and polylist are supported)")
+            LOGGER.debug("Skipping Collada geometry %s because it contains no supported surface primitives", mesh_id)
+            continue
 
         for primitive_element_set in primitive_element_sets:
             primitive_tag = _xml_local_name(primitive_element_set.tag)
@@ -124,12 +127,20 @@ def tag(name):
                     if instance_effect is not None:
                         instance_effect_id = instance_effect.attrib["url"][1:]
                         effect = effects.find('{}[@id="{}"]'.format(tag("effect"), instance_effect_id))
-                        phong = effect.find("{}/{}/{}".format(tag("profile_COMMON"), tag("technique"), tag("phong")))
-                        colors = phong.findall(".//{}".format(tag("color")))
-                        for color_node in colors:
-                            rgba = [float(i) for i in color_node.text.split()]
-                            if "sid" in color_node.attrib:
-                                mesh_colors["mesh_color.{}".format(color_node.attrib["sid"])] = rgba
+                        technique = effect.find("{}/{}".format(tag("profile_COMMON"), tag("technique")))
+                        shader = None
+
+                        for shader_name in ("phong", "lambert", "blinn", "constant"):
+                            shader = technique.find(tag(shader_name))
+                            if shader is not None:
+                                break
+
+                        if shader is not None:
+                            colors = shader.findall(".//{}".format(tag("color")))
+                            for color_node in colors:
+                                rgba = [float(i) for i in color_node.text.split()]
+                                if "sid" in color_node.attrib:
+                                    mesh_colors["mesh_color.{}".format(color_node.attrib["sid"])] = rgba
                 except Exception:
                     LOGGER.exception("Exception while loading materials, all materials of mesh file %s will be ignored ", filename)
 
@@ -191,4 +202,7 @@ def tag(name):
 
             meshes.append(mesh)
 
+    if not meshes:
+        raise Exception("No supported surface primitives found (currently only triangles and polylist are supported)")
+
     return meshes

tests/fixtures/surfaces_lines_and_empty_geometry.dae

@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="utf-8"?>
+<COLLADA xmlns="http://www.collada.org/2005/11/COLLADASchema" version="1.4.1">
+  <library_effects>
+    <effect id="red-effect">
+      <profile_COMMON>
+        <technique sid="common">
+          <lambert>
+            <diffuse>
+              <color sid="diffuse">1 0 0 1</color>
+            </diffuse>
+          </lambert>
+        </technique>
+      </profile_COMMON>
+    </effect>
+  </library_effects>
+  <library_materials>
+    <material id="red-material">
+      <instance_effect url="#red-effect"/>
+    </material>
+  </library_materials>
+  <library_geometries>
+    <geometry id="surface">
+      <mesh>
+        <source id="surface-positions">
+          <float_array id="surface-positions-array" count="9">0 0 0 1 0 0 0 1 0</float_array>
+        </source>
+        <vertices id="surface-vertices">
+          <input semantic="POSITION" source="#surface-positions"/>
+        </vertices>
+        <triangles material="red-material" count="1">
+          <input semantic="VERTEX" source="#surface-vertices" offset="0"/>
+          <p>0 1 2</p>
+        </triangles>
+      </mesh>
+    </geometry>
+    <geometry id="lines-only">
+      <mesh>
+        <source id="line-positions">
+          <float_array id="line-positions-array" count="6">0 0 0 1 0 0</float_array>
+        </source>
+        <vertices id="line-vertices">
+          <input semantic="POSITION" source="#line-positions"/>
+        </vertices>
+        <lines count="1">
+          <input semantic="VERTEX" source="#line-vertices" offset="0"/>
+          <p>0 1</p>
+        </lines>
+      </mesh>
+    </geometry>
+    <geometry id="empty">
+      <mesh>
+        <source id="empty-positions">
+          <float_array id="empty-positions-array" count="0"/>
+        </source>
+        <vertices id="empty-vertices">
+          <input semantic="POSITION" source="#empty-positions"/>
+        </vertices>
+      </mesh>
+    </geometry>
+  </library_geometries>
+</COLLADA>

tests/test_resources.py

@@ -23,3 +23,14 @@ def test_mesh_import_namespaced_collada():
     assert meshes[0].number_of_faces() == 2598
     assert meshes[1].number_of_vertices() == 1158
     assert meshes[1].number_of_faces() == 2240
+
+
+def test_mesh_import_collada_ignores_non_surface_geometry_and_loads_lambert_material():
+    filename = os.path.join(os.path.dirname(__file__), "fixtures", "surfaces_lines_and_empty_geometry.dae")
+
+    meshes = mesh_import(filename, filename)
+
+    assert len(meshes) == 1
+    assert meshes[0].number_of_vertices() == 3
+    assert meshes[0].number_of_faces() == 1
+    assert meshes[0].attributes["mesh_color.diffuse"] == [1.0, 0.0, 0.0, 1.0]