Banded Contour

This example demonstrates how to use banded contours.

📋 Summary

Uses an unstructured Met Office LFRic C48 cubed-sphere mesh of surface altitude data.

First triangulate the mesh as this is the preferred geometry when using the contour filter.

Then we threshold the surface altitude by height such that all sea-level cells are removed from the mesh.

The remaining land-based cells of the mesh are contoured and rendered using a qualitative colormap (Set3) containing 12 unique colours. We use the contour_banded filter to generate 13 contours and the associated banded contour edges.

A Natural Earth base layer is also rendered along with the Natural Earth coastlines.

Tags: component: coastlines component: texture domain: orography filter: cast filter: contour filter: threshold filter: triangulate sample: unstructured style: colormap

---

Static Scene

Interactive Scene

from __future__ import annotations

import geovista
from geovista.common import cast_UnstructuredGrid_to_PolyData as cast
from geovista.pantry.meshes import lfric_orog
import geovista.theme


def main() -> None:
    """Plot banded contours of surface altitude with a qualitative colormap.

    Notes
    -----
    .. versionadded:: 0.6.0

    """
    # Load the sample mesh.
    mesh = lfric_orog()

    # Triangulate the mesh prior to contouring.
    mesh.triangulate(inplace=True)

    # Remove only those cells where all their vertices have a surface altitude
    # below the specified height threshold.
    height = 1e-1
    mesh = cast(mesh.threshold(height, preference="point"))

    # Generate the filled contours and contour edges between bands.
    n_contours = 13
    contours, edges = mesh.contour_banded(n_contours)

    p = geovista.GeoPlotter()

    sargs = {"title": "Surface Altitude / m", "fmt": "%.0f"}
    p.add_mesh(contours, cmap="Set3", n_colors=n_contours - 1, scalar_bar_args=sargs)
    p.add_mesh(edges, color="black", zlevel=1)

    p.add_base_layer(texture=geovista.natural_earth_1())
    p.add_coastlines()

    # Render the scene using super-sample anti-aliasing.
    p.enable_anti_aliasing(aa_type="ssaa")

    # Define a specific camera position.
    p.view_vector(vector=(0, 1, 0.5))
    p.camera.zoom(1.2)

    p.add_axes()
    p.show()


if __name__ == "__main__":
    main()