Re: Finding reference to the data actually being displayed


The below approach appears to be working nicely.  The bad news is that
it appears to have maybe uncovered a "bug" in VisAD's brushing widgets
in that valid points appear to be "eliminated" because of truncating
display values at the upper end?!?  Attached is a screen dump showing
what's happening to the "f1" parameter in the data set currently being
displayed prior to any brushing operations.  f1's max is 6040.451843
while the widget is showing a max value of 6040.451, which apparently
causes that data row to be dropped from the display.  In the lower
left-hand-corner of the screen dump, you can see that the
rangeSelect[0].length is 1303, which is the correct number of rows in
the dataset, while the remainingPts is 1302, found by cycling through
the rangeSelect[][] array looking for false value.  Since no brushing
has occured, both should show 1303.  The row found to be "false" is the
row containing the f1 max of 6040.451843, which is consistent with the
above assertions.  Truncation at the lower bounds is not a problem.

thanks...  dlf


-----Original Message-----
Sent: Tuesday, March 08, 2005 11:58 AM
Cc: visad@xxxxxxxxxxxxxxxx
after brushing ...

Hi Don,

> We're doing some really vanilla 2D and 3D scatter plots loading data
into FlatField's for display.  We're also using SelectRangeWidget's for
brushing the data.  Everything's working like a charm!  Our users are
now asking to know after they finish brushing 1) how many points are
left in the original data set, and 2) can they dump the currently
displayed data to a new file now that they've filtered out all the
unwanted stuff.  To take care of this, I need to find a reference to the
"data" actually being displayed.  Following the data "trail" through the
VisAD documentation, it's not clear to me where to find the "getXXX()"
accessor to the actually displayed data set.

There is no getXXX() accessor to find the data actually
selected. But there is a way to get at it, although its
a bit complex (I'm pretty sure it'll work).

You can define a new class that extends ShadowFunctionTypeJ3D
and overrides the assembleSelect() method. This method should
just call super.assembleSelect() withits same argument, then
save a copy of the return value. This will be a "boolean[][]
range_select" array, which is dimensioned:


The true values represent the range values selected for
display. Your extension of ShadowFunctionTypeJ3D should
include a method for getting this saved range_select array.
Note you will be overriding the implementation of
assembleSelect() in visad/

You'll need another class that extends DefaultRendererJ3D
and overrides the makeShadowFunctionType() method to
construct and return an instance of your class that extends
ShadowFunctionTypeJ3D. See visad/bom/
for an example of this.

Good luck,

Attachment: brushingError.jpg
Description: brushingError.jpg