Keep mayavi as legacy fallback for backward compatibility

PyVista is the preferred 3D backend, mayavi is used as fallback when
pyvista is not installed. Existing users with mayavi setups continue
to work without changes.

Co-Authored-By: deepseek-v4-pro

Author: zhengjiang shao

vaspy/electro.py

@@ -29,13 +29,20 @@
     print('Warning: Module matplotlib.pyplot is not installed')
     plt_installed = False
 
-#whether pyvista installed
+#whether pyvista installed (preferred)
 try:
     import pyvista as pv
     pyvista_installed = True
 except ImportError:
     pyvista_installed = False
 
+#whether mayavi installed (legacy fallback)
+try:
+    from mayavi import mlab
+    mayavi_installed = True
+except ImportError:
+    mayavi_installed = False
+
 from vaspy.plotter import DataPlotter
 from vaspy.atomco import PosCar
 from vaspy.functions import line2list
@@ -462,43 +469,55 @@ def plot_contour(self, ndim0, ndim1, z, show_mode):
 
     @contour_decorator
     def plot_mcontour(self, ndim0, ndim1, z, show_mode):
-        "use PyVista to plot surface contour."
-        if not pyvista_installed:
-            self.__logger.info("PyVista is not installed on your device.")
-            return
+        "Plot surface contour using PyVista (preferred) or mayavi (legacy)."
         #do 2d interpolation
         s = np.s_[0:ndim0:1, 0:ndim1:1]
         x, y = np.ogrid[s]
-        #use cubic 2d interpolation
         interpfunc = interp2d(x, y, z, kind='cubic')
         newx = np.linspace(0, ndim0, 600)
         newy = np.linspace(0, ndim1, 600)
-        newz = interpfunc(newx, newy)  # shape: (len(newy), len(newx))
-        # Build structured surface (3D grid with thickness 1)
-        nx, ny = len(newx), len(newy)
-        X, Y = np.meshgrid(newx, newy, indexing='ij')  # (nx, ny)
-        Z = newz.T  # transpose to (nx, ny)
-        surface = pv.StructuredGrid(X[:, :, None], Y[:, :, None], Z[:, :, None])
-        surface.point_data['scalars'] = Z[:, :, None].flatten(order='F')
-        # Plot
-        pl = pv.Plotter()
-        pl.add_mesh(surface, scalars='scalars', cmap='viridis',
-                    show_scalar_bar=True)
-        pl.add_axes(xlabel='x', ylabel='y', zlabel='z')
-        #save or show
-        if show_mode == 'show':
-            pl.show()
-        elif show_mode == 'save':
-            pl.screenshot('pyvista_contour3d.png')
+        newz = interpfunc(newx, newy)
+
+        if pyvista_installed:
+            nx, ny = len(newx), len(newy)
+            X, Y = np.meshgrid(newx, newy, indexing='ij')
+            Z = newz.T
+            surface = pv.StructuredGrid(X[:, :, None], Y[:, :, None],
+                                        Z[:, :, None])
+            surface.point_data['scalars'] = Z[:, :, None].flatten(order='F')
+            pl = pv.Plotter()
+            pl.add_mesh(surface, scalars='scalars', cmap='viridis',
+                        show_scalar_bar=True)
+            pl.add_axes(xlabel='x', ylabel='y', zlabel='z')
+            if show_mode == 'show':
+                pl.show()
+            elif show_mode == 'save':
+                pl.screenshot('pyvista_contour3d.png')
+            else:
+                raise ValueError('Unrecognized show mode parameter : ' +
+                                 show_mode)
+        elif mayavi_installed:
+            face = mlab.surf(newx, newy, newz, warp_scale=2)
+            mlab.axes(xlabel='x', ylabel='y', zlabel='z')
+            mlab.outline(face)
+            if show_mode == 'show':
+                mlab.show()
+            elif show_mode == 'save':
+                mlab.savefig('mlab_contour3d.png')
+            else:
+                raise ValueError('Unrecognized show mode parameter : ' +
+                                 show_mode)
         else:
-            raise ValueError('Unrecognized show mode parameter : ' +
-                             show_mode)
+            self.__logger.warning(
+                "Neither PyVista nor mayavi is installed. "
+                "Install pyvista: pip install pyvista")
+            return
 
         return
 
     def plot_contour3d(self, **kwargs):
         '''
-        use PyVista to plot 3d isosurface contour.
+        Plot 3d isosurface contour using PyVista (preferred) or mayavi (legacy).
 
         Parameter
         ---------
@@ -510,9 +529,6 @@ def plot_contour3d(self, **kwargs):
                         number of replication on x, y, z axis,
         }
         '''
-        if not pyvista_installed:
-            self.__logger.warning("PyVista is not installed on your device.")
-            return
         # set parameters
         widths = kwargs['widths'] if 'widths' in kwargs else (1, 1, 1)
         elf_data, grid = self.expand_data(self.elf_data, self.grid, widths)
@@ -522,49 +538,69 @@ def plot_contour3d(self, **kwargs):
             self.__logger.warning("maxct is larger than %f", maxdata)
         opacity = kwargs['opacity'] if 'opacity' in kwargs else 0.6
         nct = kwargs['nct'] if 'nct' in kwargs else 5
-        # Build StructuredGrid with proper cell geometry
-        pvgrid = self._build_structured_grid(elf_data, grid)
-        # Extract isosurfaces
-        contours = pvgrid.contour(nct, scalars='values',
-                                  rng=(0, maxct) if maxct < maxdata else None)
-        # Plot
-        pl = pv.Plotter()
-        pl.add_mesh(contours, opacity=opacity, cmap='viridis',
-                    show_scalar_bar=True)
-        pl.add_axes(xlabel='a', ylabel='b', zlabel='c')
-        pl.show()
+
+        if pyvista_installed:
+            pvgrid = self._build_structured_grid(elf_data, grid)
+            contours = pvgrid.contour(nct, scalars='values',
+                                      rng=(0, maxct) if maxct < maxdata else None)
+            pl = pv.Plotter()
+            pl.add_mesh(contours, opacity=opacity, cmap='viridis',
+                        show_scalar_bar=True)
+            pl.add_axes(xlabel='a', ylabel='b', zlabel='c')
+            pl.show()
+        elif mayavi_installed:
+            surface = mlab.contour3d(elf_data)
+            surface.actor.property.opacity = opacity
+            surface.contour.maximum_contour = maxct
+            surface.contour.number_of_contours = nct
+            mlab.axes(xlabel='z', ylabel='y', zlabel='x')
+            mlab.outline()
+            mlab.show()
+        else:
+            self.__logger.warning(
+                "Neither PyVista nor mayavi is installed. "
+                "Install pyvista: pip install pyvista")
+            return
 
         return
 
     def plot_field(self, **kwargs):
-        "Plot scalar field volume with interactive cut plane."
-        if not pyvista_installed:
-            self.__logger.warning("PyVista is not installed on your device.")
-            return
-        # set parameters
+        "Plot scalar field volume using PyVista (preferred) or mayavi (legacy)."
         vmin = kwargs['vmin'] if 'vmin' in kwargs else 0.0
         vmax = kwargs['vmax'] if 'vmax' in kwargs else 1.0
         axis_cut = kwargs.get('axis_cut', 'z')
         nct = kwargs['nct'] if 'nct' in kwargs else 5
         widths = kwargs['widths'] if 'widths' in kwargs else (1, 1, 1)
         elf_data, grid = self.expand_data(self.elf_data, self.grid, widths)
-        # Build StructuredGrid with proper cell geometry
-        pvgrid = self._build_structured_grid(elf_data, grid)
-        # Determine cut plane normal
-        normals = {'x': (1, 0, 0), 'y': (0, 1, 0), 'z': (0, 0, 1)}
-        normal = normals.get(axis_cut.lower(), (0, 0, 1))
-        # Slice through center
-        center = pvgrid.center
-        single_slice = pvgrid.slice(normal=normal, origin=center)
-        # Contours on the slice
-        edges = single_slice.contour(nct, scalars='values')
-        # Plot
-        pl = pv.Plotter()
-        pl.add_volume(pvgrid, scalars='values', clim=(vmin, vmax),
-                      cmap='viridis', opacity='linear')
-        pl.add_mesh(edges, color='black', line_width=1)
-        pl.add_axes(xlabel='a', ylabel='b', zlabel='c')
-        pl.show()
+
+        if pyvista_installed:
+            pvgrid = self._build_structured_grid(elf_data, grid)
+            normals = {'x': (1, 0, 0), 'y': (0, 1, 0), 'z': (0, 0, 1)}
+            normal = normals.get(axis_cut.lower(), (0, 0, 1))
+            center = pvgrid.center
+            single_slice = pvgrid.slice(normal=normal, origin=center)
+            edges = single_slice.contour(nct, scalars='values')
+            pl = pv.Plotter()
+            pl.add_volume(pvgrid, scalars='values', clim=(vmin, vmax),
+                          cmap='viridis', opacity='linear')
+            pl.add_mesh(edges, color='black', line_width=1)
+            pl.add_axes(xlabel='a', ylabel='b', zlabel='c')
+            pl.show()
+        elif mayavi_installed:
+            field = mlab.pipeline.scalar_field(elf_data)
+            mlab.pipeline.volume(field, vmin=vmin, vmax=vmax)
+            plane_map = {'z': 'z_axes', 'y': 'y_axes', 'x': 'x_axes'}
+            orientation = plane_map.get(axis_cut.lower(), 'z_axes')
+            cut = mlab.pipeline.scalar_cut_plane(
+                field.children[0], plane_orientation=orientation)
+            cut.enable_contours = True
+            cut.contour.number_of_contours = nct
+            mlab.show()
+        else:
+            self.__logger.warning(
+                "Neither PyVista nor mayavi is installed. "
+                "Install pyvista: pip install pyvista")
+            return
 
         return