[yt-users] ProjectionTransferFunction with Camera

[Sam Skillman]

Hi Munier,

I can reproduce the issue you see there using the Camera interface, and am
not sure at the moment why that doesn't work. However, there are several
alternate methods that may be more useful that are constructed specifically
for off axis projections.

The first is the off_axis_projection function:
http://yt-project.org/docs/dev/visualizing/plots.html#off-axis-projection-plots

A while back this was wrapped with an OffAxisProjectionPlot Plot-window
interface, which can been seen just below the example linked to above.

Finally, you could use the ProjectionCamera class, which inherits a lot of
characteristics from the Camera class.  Here's an example on how to run it
(modified version of your code above):
http://paste.yt-project.org/show/4257/

Note that the off_axis_projection function actually just wraps the
ProjectionCamera class, and OffAxisProjectionPlot wraps
off_axis_projection, so it's all the same underneath.

Let us know if that works. I'd suggest you go with the
OffAxisProjectionPlot interface since it is meant to be similar to the
SlicePlot/ProjectionPlot.

Sam


On Wed, Jan 29, 2014 at 7:13 AM, Munier Azzam Salem <
msalem at astro.columbia.edu> wrote:

> Hey Guys,
>
>      I'm trying to get simple projections, but using the Camera interface,
> to allow skewed perspectives. I've tried simply allowing the camera to use
> the default ProjectionTransferFunction, in lieu of prettier color transfer
> functions ... this seems to yield an all-black image. I've also tried
> explicitly setting it's bounds (both with log and non-log limits). This
> doesn't seem to help. I see this issue came up about a year ago here<http://lists.spacepope.org/pipermail/yt-users-spacepope.org/2013-January/003285.html>
> .
>
>        My script's included below. I'm tempted to just tweak my inputs to
> the color trasnfer function to mimic a simple projection.
>
>          thanks!
>              Munier
>
> My script:
>
> *from yt.mods import **
> *import yt.visualization.volume_rendering.api as vr*
> *from yt.visualization.volume_rendering.transfer_functions import
> ProjectionTransferFunction as PTF*
>
> *pf = load("DD0179/DD0179")*
> *field = 'Density'*
> *use_log = True*
>
> *# Find the bounds in log space of for your field*
> *dd = pf.h.all_data()*
> *limits = np.array(dd.quantities["Extrema"](field)[0]) * pf.units['cm']*
>
> *#if use_log:*
> *#    limits = np.log(limits)*
>
> *# Set up the camera parameters: center, looking direction, width,
> resolution*
>  *c = np.array([.333]*3)*
> *L = np.array([1.0, 1.0, 1.0])*
> *W = 0.3 / pf["unitary"]*
> *N = 1028*
>
> *# Create a camera object*
> *cam = vr.Camera(c, L, W, (N,N), transfer_function=PTF(limits),pf=pf)*
> *im = cam.snapshot('density.png')*
>
> --
> Munier A. Salem // 845.489.6450
>
> _______________________________________________
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>
>
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