feature: Add vtp support

  Starting from the vtu implementation worked through adding vtp support.
  Currently meshio doesn't support triangle strips, and not clear
  reason to do so. This means that on read triangle strips get
  converted to triangles, which become polygons on write to vtp.

  Merges triangles, quads, and polygons into polygons on
  write. The read process specifies the cell types into the same
  triangles, quads, and polygons.

  Cell dell data from triangle strips gets duplicated for the
  decomposed triangle strips.

  Rebase/squashed from original draft

  Resolve #527

.gitattributes

@@ -8,6 +8,7 @@
 *.ply filter=lfs diff=lfs merge=lfs -text
 *.vtk filter=lfs diff=lfs merge=lfs -text
 *.vtu filter=lfs diff=lfs merge=lfs -text
+*.vtp filter=lfs diff=lfs merge=lfs -text
 *.ugrid filter=lfs diff=lfs merge=lfs -text
 *.mesh filter=lfs diff=lfs merge=lfs -text
 *.meshb filter=lfs diff=lfs merge=lfs -text

src/meshio/__init__.py

@@ -27,6 +27,7 @@
     tetgen,
     ugrid,
     vtk,
+    vtp,
     vtu,
     wkt,
     xdmf,
@@ -71,6 +72,7 @@
     "tetgen",
     "ugrid",
     "vtk",
+    "vtp",
     "vtu",
     "wkt",
     "xdmf",

src/meshio/_cli/_ascii.py

@@ -49,6 +49,8 @@ def ascii(args):
         stl.write(args.infile, mesh, binary=False)
     elif fmt == "vtk":
         vtk.write(args.infile, mesh, binary=False)
+    elif fmt == "vtp":
+        vtk.write(args.infile, mesh, binary=False)
     elif fmt == "vtu":
         vtu.write(args.infile, mesh, binary=False)
     elif fmt == "xdmf":

src/meshio/_cli/_binary.py

@@ -48,6 +48,8 @@ def binary(args):
         stl.write(args.infile, mesh, binary=True)
     elif fmt == "vtk":
         vtk.write(args.infile, mesh, binary=True)
+    elif fmt == "vtp":
+        vtk.write(args.infile, mesh, binary=True)
     elif fmt == "vtu":
         vtu.write(args.infile, mesh, binary=True)
     elif fmt == "xdmf":

src/meshio/_cli/_compress.py

@@ -61,6 +61,10 @@ def compress(args):
         stl.write(args.infile, mesh, binary=True)
     elif fmt == "vtk":
         vtk.write(args.infile, mesh, binary=True)
+    elif fmt == "vtp":
+        vtu.write(
+            args.infile, mesh, binary=True, compression="lzma" if args.max else "zlib"
+        )
     elif fmt == "vtu":
         vtu.write(
             args.infile, mesh, binary=True, compression="lzma" if args.max else "zlib"

src/meshio/vtp/__init__.py

@@ -0,0 +1,3 @@
+from ._vtp import read, write
+
+__all__ = ["read", "write"]