Using QuickView in Py-SPHViewer

QuickView is the simplest way to produce an image with Py-SPHViewer. Here we use a simple example that illustrates its use.

Looking at a dark matter halo with QuickView

In this example we will create an image of a dark matter halo extracted from a cosmological simulation. Before starting the tutorial please download this file.

We can read the content of the file using the h5py library:

import h5py

with h5py.File('dm_halo.h5py','r') as f:
    pos = f['Coordinates'].value

The coordinates of the dark matter particles are expressed in Mpc/h, and they trace the density field of a collapsed dark matter halo extracted from a cosmological simulation. Our goal will be to visualise the projected density field.

The image below shows the xy projection of the distribution of particles:

First image with QuickView

The projected density field can be calculated (and visualised) using QuickView:

from sphviewer.tools import QuickView
qv = QuickView(pos, r='infinity', plot=False)
qv.imshow()

First image with QuickView

The argument r=’infinity’ indicates that the camera is looking at the scene from the infinity, so that the scene has to be rendered using a parallel (or orthographic) projection.

QuickView retrieves the active axis and places the image on it; plot=False prevents this from happening. QuickView objects have an associated imshow method to show the final image. Valid *kwargs are identical to those accepted by matplotlib.pyplot.imshow. For example, we can change the colormap and vmin as follows:

qv.imshow(cmap="gist_stern", vmax=2)

First image with QuickView

There are also methods to retrieve the image generated by QuickView:

img = qv.get_image()
extent = qv.get_extent()
fig = plt.figure(1, figsize=(7,7))
plt.imshow(img, extent=extent, cmap='gist_stern')

First image with QuickView