Fits Realtime Explorer of Low Latency in Every Dimension

 Complete archive of all FRELLED versions available here. User guide here. The downloads come with a PDF manual but it's obsolete apart from the moose jokes - use the web version instead !

3D data should be viewed in 3D. Most astronomy programs don't let you do that, and those that do often have fatal flaws (or treat the 3D as a sort of cheap gimmick that's only good for making pretty movies). To overcome this I wrote a set of Python scripts for Blender that let you import the data and view it with Blender's extremely well-developed interface. This means you can view the data in 3D from any angle you like. There are no clunky pitch/yaw/roll sliders as with other viewers : you rotate the view with the mouse and the view updates instantly, more like in a computer game than in an astronomical program.

Placing the view inside the data is just as easy as viewing from outside - there's even a flight sim mode. You can also switch to a more conventional 2D mode where you view the data slice-by-slice. Various colour controls give you a lot of options as to how the data is displayed, but there are also auto-import buttons if you just want to load the frickin' file already.


FRELLED is designed for astronomers with no knowledge of Blender. It has a user non-hostile GUI (unlike my previous efforts), and the quick start guide is truly unique. Although geared for astronomy, it can also be adpated for any 3D data set. If you can make a sequence of images, you can load them into FRELLED.


FRELLED was originally written to make HI data analysis easier (read more here). Originally it was highly specialised and only really worked with very specific data. It's under active development and now supports quite a lot more than its original goals. Main features :

- 3D and 2D display modes. Up to 600^3 voxels in realtime.

- Linear or logarithmic scales for the colour range.

- Data values can simultaneously affect the transparency and colour in different ways.

- Option to automatically stretch data with weird aspect ratios into a cube.

- Interactively mask data by defining regions (of arbitrary shapes, including monkeys [link]). Masks can be toggled on and off.

- Sum the flux in specified region and correct for the beam shape.

- Query NED and the SDSS.

- One-button download and overlay SDSS RGB images with the data.

- Generate flux maps, contour plots and renzograms, all of which can be overlaid with the raw data.

- Generate axes around maps for producing plots.

- Supports equatorial and galactic coordinates using SIN and CAR projection types.

- Other data sets use pixels instead of world coordinate - useful for simulation data.

- Easily set up turntable movies to win friends and influence people.

- Load in a sequence of FITS files and generate movies, useful for simulations.

- Overlay vectors and n-body particles.

More information about the motivation and development of FRELLED can be found here.

FRELLED requires Blender 2.49 (NOT the latest version of Blender), any version of Python 2.6, and the pyfits, numpy and matplotlib modules. Full installation instructions can be found in the manual. Since it's Blender and Python, operating system is irrelevant. However, it's known to be extremely difficult to install on a Linux network. I recommend you get your system adminstator to install it locally.

I've used FRELLED to participate in the National Science Foundation's annual International Science and Engineering Visualisation Challenge (yes, I think they could have thought of a shorter title too). This video shows the Universe as seen in neutral hydrogen, starting from our own galaxy and finishing more than a bilion light years away.

Note : if you're using FRELLED (for any reason), I'd love to hear from you ! A mailing list is available if you want notification of the latest updates (generally a few times per year).

If you're using FRELLED for science and you really want to show your appreciation, consider citing the following paper :

FRELLED : A realtime volumetric data viewer for astronomers

Taylor, R., 2015, A&C, 13, 67


Alternatively, FRELLED was first formally described briefly in this paper

The Arecibo Galaxy Environment Survey - VII. A dense filament with extremely long H I streams

Taylor, R.; Minchin, R. F.; Herbst, H.; Davies, J. I.; Rodriguez, R.; Vazquez, C., 2014, MNRAS, 443, 2634

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