RE: slow 2d image generation

• To: <tomw@xxxxxxxxxxxxx>
• Subject: RE: slow 2d image generation
• From: "Jim Cookas" <James.M.Cookas@xxxxxxxx>
• Date: Tue, 6 Jan 2004 15:15:58 -0600

tom, all

thanks a ton for the suggestion...it looks like this will be the method of 
choice for speeding up image display...i implemented the changes today, but i'm 
having a problem getting the image to display...i think it is a problem with my 
ascii file format...

i am using tab-spaced values...here is what test.tsv looks like:


(Down_Range,Cross_Range)->(RCS)
Down_Range[-755.383:755.383]    Cross_Range[-755.383:755.383]   RCS
[ 256 RCS values for Down_Range #0 ]
[ 256 RCS values for Down_Range #1 ]
.
.
.
[ 256 RCS values for Down_Range #255 ]


when i try to load this file into visad, i get these messages at the terminal:


Unit name problem:visad.data.units.ParseException: negative sign follows 
decimal point with -755.383:755.383
Unit name problem:visad.data.units.ParseException: negative sign follows 
decimal point with -755.383:755.383


any ideas on the problem?...thanks again!!

jc

> -----Original Message-----
> From: Tom Whittaker [mailto:tomw@xxxxxxxxxxxxx]
> Sent: Monday, January 05, 2004 9:43 PM
> To: Jim Cookas
> Cc: Jim Koutsovasilis; visad@xxxxxxxxxxxxxxxx
> Subject: Re: slow 2d image generation
> 
> 
> Jim:
> 
> I believe that part of the slowness in "reading" is that the form of 
> your data is producing an IrregularSet, which VisAD needs to 
> "triagulate" when it does the display.  If your data points are a 
> "regular grid" (meaning, regular/constant spacing between 
> data points) 
> you can use the format:
> 
> Down_Range[-755.383:-200], Cross_Range[-755.838:-500], RCS
> 
> (where the '-200' and '-500' should be the actual ending 
> values for the 
> sample domain.  If you do this, and then put all the RCS 
> values (along 
> the Cross_Range)for a single Down_Range on one input line.  The text 
> reader will compute the actual domain sampling coordinate for 
> each "RCS" 
> value.  When you do this, the TextAdapter will make a 
> Gridded2DSet for 
> the sampling domain, and it is handled faster than the IrregularSet.
> 
> Of course, there will be some overhead for reading and 
> decoding the text 
> in either case, so I agree with JimK -- you may want to 
> create your own 
> reader.
> 
> tom

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