Hi Libby, There are a couple ways to do this that come to mind right away. Unfortunately, calculating the exact solid angle that a cell subtends can be a bit tricky, but otherwise this is precisely the kind of analysis yt is designed to do. 1) Bin based on the solid angle, approximating this by, for instance, assuming that the cell is hit face on such that the area that it covers is dx^2. (This assumes cubical cells, though.) 2) Actually integrate out and accumulate the values you are interested in. This would require using the HEALpix camera, which is described here http://yt.enzotools.org/doc/visualizing/volume_rendering.html and on the blog. You could, for instance, take just a ProjectionTransferFunction and apply that to an integration of a field that has cutoffs based on the solid angle. The HEALpix camera performs an all-sky integration calculated from a central point; this can be used for quantitative integration and analysis of field values. There may be other ways, though -- maybe somebody else has some other ideas? -Matt On Mon, May 16, 2011 at 12:33 PM, Elizabeth Harper-Clark wrote:

Hi Guys,

Is there a way to quantify values in yt by solid angle around a point?

For example I have a simulation of star clusters forming within a turbulent GMC. When a bubble is present I want to calculate the covering fraction of the shell. One way to do this would be using where the radiation pressure is absorbed and calculate the fraction of solid angle (around the oldest cluster) radiation pressure is absorbed above a minimum value out to a given radius. See attached for projections of this simulation at a time with a bubble shell! (bottom left shows radiation pressure absorption).

Has anyone written any code/script to calculate solid angle before?

Many thanks,

Libby

-- Elizabeth Harper-Clark MA MSci PhD Candidate, Astrophysics, UofT

www.astro.utoronto.ca/~h-clark h-clark@cita.utoronto.ca AIM: edphc1 MSN: edphc1@hotmail.com Skype: eharperclark Office phone: 416-978-5759

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