Add visuals.glvis beta version (#827)

skfem/visuals/glvis.py

@@ -0,0 +1,103 @@
+import skfem
+import io
+import numpy as np
+
+from typing import Optional
+from glvis import glvis
+
+
+MESH_TYPE_MAPPING = {
+    skfem.MeshTet1: 4,
+    skfem.MeshTri1: 2,
+    skfem.MeshQuad1: 3,
+    skfem.MeshLine1: 1,
+}
+
+
+BOUNDARY_TYPE_MAPPING = {
+    4: 2,
+    2: 1,
+    3: 1,
+    5: 3,
+}
+
+
+template = """solution
+
+MFEM mesh v1.0
+
+dimension
+{}
+
+elements
+{}
+{}
+
+boundary
+{}
+{}
+
+vertices
+{}
+{}
+{}
+
+FiniteElementSpace
+FiniteElementCollection: {}
+VDim: {}
+Ordering: 0
+{}
+
+{}
+"""
+
+
+def _to_int_string(arr):
+    s = io.BytesIO()
+    np.savetxt(s, arr, delimiter=' ', fmt='%d')
+    return s.getvalue().decode()
+
+
+def _to_float_string(arr):
+    s = io.BytesIO()
+    np.savetxt(s, arr, delimiter=' ')
+    return s.getvalue().decode()
+
+
+def plot(basis, x, keys: Optional[str] = None):
+    m = basis.mesh
+    if isinstance(basis.elem, skfem.ElementVector):
+        vdim = m.dim()
+        x = x.reshape((-1, vdim)).flatten('F')
+    else:
+        vdim = 1
+    bfacets = m.boundary_facets()
+    nbfacets = len(bfacets)
+    return glvis(template.format(
+        m.dim(),
+        m.nelements,
+        _to_int_string(np.hstack((
+            np.ones(m.nelements, dtype=np.int64)[:, None],
+            (np.zeros(m.nelements, dtype=np.int64)[:, None]
+             + MESH_TYPE_MAPPING[type(m)]),
+            m.t.T,
+        ))),
+        nbfacets,
+        _to_int_string(np.hstack((
+            np.ones(nbfacets, dtype=np.int64)[:, None],
+            (np.zeros(nbfacets, dtype=np.int64)[:, None]
+             + BOUNDARY_TYPE_MAPPING[MESH_TYPE_MAPPING[type(m)]]),
+            m.facets[:, bfacets].T,
+        ))),
+        m.nvertices,
+        m.doflocs.shape[0],
+        _to_float_string(m.doflocs.T),
+        'Linear',
+        vdim,
+        _to_float_string(x[:, None]),
+        "keys\n{}".format(keys) if keys is not None else "",
+    ))
+
+
+def draw(basis, keys: Optional[str] = None):
+    return plot(basis, basis.zeros(), keys=keys)