Mesh class for merging multiple meshes from the Scaffold class

src/sparc_spy/mesh.py

@@ -1,3 +1,70 @@
-class Mesh(object):
+import os 
+import shutil
+import pyvista as pv
+from io import StringIO
+
+class Meshes(object):
     def __init__(self) -> None:
-        pass
+        self.meshes = pv.MultiBlock()  
+
+    def add_mesh(self, label: str, mesh: pv.PolyData): 
+        self.meshes.append(label, mesh) 
+
+    def export(self, output_filepath: str = "output.stl", base_path='.'):  
+        save_multiblock_stl(self.meshes, output_filepath, base_path) 
+
+    def items(self):
+        items = []
+        for key in self.meshes.keys():
+            items.append((key, self.meshes[key]))
+        return items
+
+
+def save_multiblock_stl(multiblock, filename, base_path='.'):
+
+    names = multiblock.keys()
+    oname, ext = os.path.splitext(filename)
+    assert ext == '.stl'
+
+    # each individual stl file saved (output_filenames)
+    ofiles = [os.path.join(base_path, f'{oname}_{ii}') + '.stl' for ii in range(len(names))]
+
+    for ii, subpart in enumerate(multiblock):
+        subpart.save(ofiles[ii], binary=False)
+        change_first_line_of_file(ofiles[ii], f'solid {names[ii]}') # basically changes "solid" to "solid <solid_name>"
+
+    # merge files together
+    total_stl = ''
+    for fn in ofiles:
+        f = open(fn)
+        total_stl += f.read()
+        f.close()
+
+    # writes total stl file 
+    total_file_name = os.path.join(base_path, oname + '.stl')
+    with open(total_file_name, 'w') as f:
+        f.write(total_stl)
+
+    # deletes previously written stl files
+    for fn in ofiles:
+        os.remove(fn)
+
+    return
+
+def change_first_line_of_file(filename, new_first_line):
+
+    fr = open(filename, 'r')
+    first_line = fr.readline()
+    fr.close()
+    first_line_len = len(first_line)
+
+    new_first_line_len = len(new_first_line)
+    spaces_num = first_line_len - new_first_line_len
+    new_first_line = new_first_line + ' '*(spaces_num-1) + '\n'
+    fw = StringIO(new_first_line)
+    fr = open(filename, 'r+')
+    shutil.copyfileobj(fw, fr)
+    fr.close()
+    fw.close()
+    return
+