Helper functions for gismo export

examples/export_gismo.py

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+"""
+Export to g+smo-compatible xml-file.
+
+Recreates poisson2d_bvp.xml from gismo repo
+(see https://github.com/gismo/gismo/blob/stable/filedata/pde/poisson2d_bvp.xml)
+"""
+
+import splinepy as spp
+from splinepy.io import gismo
+
+EPS = 1e-8
+
+
+def create_geometry():
+    """Recreate multipatch geometry from g+smo repository
+
+    Returns
+    ---------
+    multipatch: splinepy Multipatch
+        Arc geometry consisting of two patches
+    """
+    # Create example's inner and outer arcs as NURBS patches with predefined values
+    arc_inner = spp.NURBS(
+        degrees=[1, 2],
+        knot_vectors=[[0.0, 0.0, 1.0, 1.0], [0.0, 0.0, 0.0, 1.0, 1.0, 1.0]],
+        control_points=[
+            [1.0, 0.0],
+            [2.0, 0.0],
+            [1.0, 1.0],
+            [2.0, 2.0],
+            [0.0, 1.0],
+            [0.0, 2.0],
+        ],
+        weights=[1.0, 1.0, 0.707106781186548, 0.707106781186548, 1.0, 1.0],
+    )
+
+    arc_outer = arc_inner.copy()
+    arc_outer.control_points = [
+        [2.0, 0.0],
+        [3.0, 0.0],
+        [2.0, 2.0],
+        [3.0, 3.0],
+        [0.0, 2.0],
+        [0.0, 3.0],
+    ]
+
+    # Initialize Multipatch object
+    multipatch = spp.Multipatch(splines=[arc_inner, arc_outer])
+    multipatch.determine_interfaces()
+
+    # Identify the patches' boundaries which correspond to the Dirichlet BCs
+    # Points with y=0 or (x=0 and y=2) are identified as Dirichlet boundaries
+    def dirichlet_identifier(points):
+        return (points[:, 1] < EPS) | (
+            (points[:, 0] < EPS) & (points[:, 1] > 2 - EPS)
+        )
+
+    # Set Dirichlet boundaries to "BID2", Neumann BCs correspond to "BID1"
+    multipatch.boundary_from_function(dirichlet_identifier, boundary_id=2)
+
+    return multipatch
+
+
+def generate_additional_xml_blocks():
+    """
+    Create blocks for rhs, manufactured solution, boundary conditions and assembly
+    options.
+
+    Returns
+    -----------
+    additional_blocks: list<dict>
+        List of dictionaries used for splinepy's gismo export function
+    """
+
+    additional_blocks = gismo.AdditionalBlocks()
+
+    # Create function block for rhs
+    additional_blocks.add_function(
+        dim=2,
+        block_id=1,
+        function_string="2*pi^2*sin(pi*x)*sin(pi*y)",
+        comment="Right-hand side function",
+    )
+
+    # Create function block for manufactured solution
+    additional_blocks.add_function(
+        dim=2,
+        block_id=3,
+        function_string="sin(pi*x) * sin(pi*y)",
+        comment="The manufactured exact solution (for reference)",
+    )
+
+    # Create block for boundary conditions
+    additional_blocks.add_boundary_conditions(
+        block_id=2,
+        dim=2,
+        function_list=[
+            "sin(pi*x) * sin(pi*y)",
+            ("pi*cos(pi*x) * sin(pi*y)", "pi*sin(pi*x) * cos(pi*y)"),
+            "0",
+        ],
+        bc_list=[("BID2", "Dirichlet", 0), ("BID1", "Neumann", 1)],
+        cv_list=[
+            ("0", "0", "1", "0"),
+            ("0", "0", "2", "sin(x)"),
+        ],  # unknown, patch, corner, function
+        unknown_id=0,
+        multipatch_id=0,
+        comment="The boundary conditions (multipatch=number of patches)",
+    )
+
+    # Create dictionary for assembly options
+    additional_blocks.add_assembly_options(
+        block_id=4, comment="Assembler options"
+    )
+
+    return additional_blocks.to_list()
+
+
+if __name__ == "__main__":
+    multipatch = create_geometry()
+
+    additional_blocks = generate_additional_xml_blocks()
+
+    # Visualize geometry and BCs
+    boundary_names = ["Neumann boundary", "Dirichlet boundary"]
+    # spp.show(
+    #     ["Multipatch", multipatch],
+    #     *[
+    #         [
+    #             f"BID{i+1}: {boundary_names[i]}",
+    #             multipatch.boundary_multipatch(i + 1),
+    #         ]
+    #         for i in range(len(multipatch.boundaries))
+    #     ],
+    #     control_points=False,
+    # )
+
+    # Export multipatch geometry and additional options/functions to an XML file
+    gismo.export(
+        fname="poisson2d_bvp_recreation.xml",
+        multipatch=multipatch,
+        indent=True,
+        additional_blocks=additional_blocks,
+    )