# Core API#

The Visualization Toolkit (VTK), developed by Kitware, has many mesh data types that PyVista wraps. This chapter is intended to describe these different mesh types and how we wrap and implement each of those mesh types in VTK. This chapter also highlights how all PyVista types have direct access to common VTK filters (see Filters).

All PyVista meshes inherit from the DataSet type (see Data Sets). PyVista has the following mesh types:

`pyvista.PointSet`

is used to represent a set of points. This is to provide an interface for datasets that explicitly use “point” arrays to represent geometry. The`pyvista.PointSet`

class is an extension of vtk.vtkPointSet.`pyvista.PolyData`

consists of any 1D or 2D geometries to construct vertices, lines, polygons, and triangles. We generally use`pyvista.PolyData`

to construct scattered points and closed/open surfaces (non-volumetric datasets). The`pyvista.PolyData`

class is an extension of vtk.vtkPolyData.A

`pyvista.UnstructuredGrid`

is the most general dataset type that can hold any 1D, 2D, or 3D cell geometries. You can think of this as a 3D extension of`pyvista.PolyData`

that allows volumetric cells to be present. It’s fairly uncommon to explicitly make unstructured grids but they are often the result of different processing routines that might extract subsets of larger datasets. The`pyvista.UnstructuredGrid`

class is an extension of vtk.vtkUnstructuredGrid.A

`pyvista.StructuredGrid`

is a regular lattice of points aligned with internal coordinate axes such that the connectivity can be defined by a grid ordering. These are commonly made from`numpy.meshgrid()`

. The cell types of structured grids must be 2D quads or 3D hexahedra. The`pyvista.StructuredGrid`

class is an extension of vtk.vtkStructuredGrid.A

`pyvista.RectilinearGrid`

defines meshes with implicit geometries along the axis directions that are rectangular and regular. The`pyvista.RectilinearGrid`

class is an extension of vtk.vtkRectilinearGrid.Image data, commonly referred to as uniform grids, and defined by the

`pyvista.UniformGrid`

class are meshes with implicit geometries where cell sizes are uniformly assigned along each axis and the spatial reference is built out from an origin point. The`pyvista.UniformGrid`

class is an extension of vtk.vtkImageData.`pyvista.MultiBlock`

datasets are containers to hold several VTK datasets in one accessible and spatially referenced object. The`pyvista.MultiBlock`

class is an extension of vtk.vtkMultiBlockDataSet.