overlay of graphics with transparency

[matei]

I would like to be able to overlay different components of the
solution vector on the same image, while using some transparency in
order to visualize both fields. Can this be done with the current
machinery?
Thanks,
matei

[James Quirk]

Matei,

The answer is a qualified yes. The attached scripts show it
is possible to position two plots on top of one another and
vary the opacity of the top most script. You run them in order:

amrita my.script
amrita my.doc

but the result is not too useful.

It's also worth noting that plot image can layer plots directly.
For when using an rgb shading function a cell is treated as
fully transparent when one of the r,g,b components is less than zero.
Thus one could plot a schlieren and then plot on top the regions where
fuelel was greater than some threshold. You might do this say when
looking at the unburnt pockets of fuel in a cellular detonation.

James
> Thanks,
> matei
>
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[Matei Radulescu]

James,
This is very helpful, thanks.
matei

[matei]

James, this is very nice. I got goosebumps when toggling through the
pages with my mouse roller. Now add a slider bar to that and you got
a pretty nifty tool to analyze the flow. Beats my old approach of
importing the images to gimp and manually changing the transparency to
see the correlation among the fields (better yet than printing them on
light paper and looking against a luminous background!)

>  my.script
> 4KViewDownload
>
>  my.doc
> 1KViewDownload

[James Quirk]

Matei,

On Thu, 10 Dec 2009, matei wrote:

> James, this is very nice. I got goosebumps when toggling through the
> pages with my mouse roller. Now add a slider bar to that and you got
> a pretty nifty tool to analyze the flow. Beats my old approach of
> importing the images to gimp and manually changing the transparency to
> see the correlation among the fields (better yet than printing them on
> light paper and looking against a luminous background!)

Attached are some more goosebumps! :-)

This time I'm using Adobe Reader's flash engine. You can plot either the
density or pressure fields and when both fields are plotted you can use
the opacity slider to fade from the pressure field to the density field.
If you look carefully, you'll see some plotting artifacts. Ignore these
for now, I know how to get rid of them, but it will take more time than I
have at present.

Indeed, for the sake of some elbow grease, there's no reason
why the simulation itslef could not be run directly in the document.

James

[matei]

> This time I'm using Adobe Reader's flash engine. You can plot either the
> density or pressure fields and when both fields are plotted you can use
> the opacity slider to fade from the pressure field to the density field.

That's very impressive!

[James Quirk]

It will be more impressive when I figure out how to allow
the interested reader to symolically program what they
want to plot. That way people won't be stuck with the
pre-supplied functions.