[yt-users] Volume Rendering and Weighted Fields

[Matthew Turk]

Hi John,

Sam's right that you could set up a derived field to do this.  I
believe, however, that the functionality is already in the existing
volume rendering code.  Sam's way may be easier.

You should be able to set up a set of multiple fields in your Camera
object when you create it.  Then, construct a
MultiVariateTransferFunction.  Add on a field table that executes a
projection, similar to the ProjectionTransferFunction.  Then simply
set the weight_field value of your new transfer function to be equal
to the field id of the weighting field; in this case it might be "0"
for the main field, "1" for the weighting field.

But, much like the projections, this should be easier -- right now I
have been taking a lot of off-axis averages and projections, and I
usually use Sam's method.  But there should be shortcuts and whatnot
for this.

Best,

Matt

On Sat, Mar 12, 2011 at 4:24 PM, John ZuHone <jzuhone at cfa.harvard.edu> wrote:
> Hi all,
>
> I have figured out how to do an off-axis projection using the camera interface, it was actually pretty straightforward.
>
> I'm primarily concerned with simulating X-ray images for clusters, and I would like to extend my process to projections of weighted quantities, say emission-weighted temperature (or "spectroscopic-like" temperature, which means weighting by dens*temp**(-alpha)).
>
> I imagine that I have to use MultiVariateTransferFunction for this... does anyone have a good example of how to do something like this? I've looked at the source code but the process is still not exactly transparent to me.
>
> Best,
>
> John ZuHone
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