Ghosts and Extents (was [vtkusers] vtkImageImport in java?)

[Stewart, Terry]

Steve,

  OK, thanks.   Updating the JNI logic was an idea that my team had been
contemplating.  Thanks for the confirmation.  And right, the interface
updates we'd like to make would likely be different than yours, so no
problem there.  

  Thanks again.

Terry

>-----Original Message-----
>From: Steve M. Robbins [mailto:steven.robbins at videotron.ca] 
>Sent: Thursday, February 09, 2006 3:08 PM
>To: Stewart, Terry
>Cc: vtkusers at vtk.org
>Subject: Re: Ghosts and Extents (was [vtkusers] vtkImageImport 
>in java?)
>
>On Thu, Feb 09, 2006 at 10:35:49AM -0800, Stewart, Terry wrote:
>> 
>> Steve,
>> 
>>   I'm using Java and ran into a similar situation while 
>trying to get 
>> my internally-generated RGB image into vtkImageData.  I'd tried the 
>> vtkImageImport path too only to run into the same roadblock with the 
>> missing [Copy|Set]ImportVoidPointer() methods for Java.  I've gotten 
>> my logic to a functional state via:
>> 
>>    vtkImageData imageData = new vtkImageData();
>>          :
>>    for (x = 0; ...)
>>       for (y = 0; ... )
>>          imageData.SetScalarComponentFromDouble(x, y, 0, rComp, 
>> (double) buffer[byteIndex++]);
>>          imageData.SetScalarComponentFromDouble(x, y, 0, gComp, 
>> (double) buffer[byteIndex++]);
>>          imageData.SetScalarComponentFromDouble(x, y, 0, bComp, 
>> (double) buffer[byteIndex++]);
>> 
>> However this is quite slow. 
>
>Yep.
>
>> Did you use some other mechanism to get your image data 
>inserted into 
>> vtkImageData that is perhaps more efficient?
>
>Yep.  We wrote JNI code that effectively does a memcpy() to 
>vtkImage.GetVoidPointer().  I'd give you the code except that 
>the JNI bit is very specific to our application so it really 
>wouldn't help you.
>
>
>-Steve
>P.S.  I still don't know what ghost levels are.  Anyone?
>
>
>
>> >On Fri, Jan 28, 2005 at 03:25:44PM -0500, Steve M. Robbins wrote:
>> >
>> >> Has anyone got example code that builds image data from
>> >scratch in Java?
>> >> Ultimately I'd like a vtkImageData object.
>> >> 
>> >> I considered using vtkImageImport in java but there doesn't
>> >appear to
>> >> be any access to the two methods that actually copy data:
>> >> CopyImportVoidPointer() and SetImportVoidPointer().  :-/
>> >
>> >I went back to copying the data directly into a vtkImageData object 
>> >and finally managed to get things working.  It turns out that the 
>> >only bit that I had missed initially was to call SetWholeExtent().  
>> >Using just SetExtent() is not enough, it seems.
>> >
>> >
>> >I have read the VTK User's Guide.  The chapter on how the pipeline 
>> >operates is helpful, but I'm still not sure exactly what is the 
>> >distinction between "extent", "whole extent" and "update 
>extent".  I 
>> >get the feeling that the update extent is set at the output end of 
>> >the pipeline (e.g. by mappers) and propagated backwards towards the 
>> >source objects, but even that is not clear.  Who is responsible for 
>> >setting the other two extents?  And what is a "ghost level"?
>> >
>> >Is there any documentation that defines these terms?
>> >
>> >How about source code: is there a particularly good class to start 
>> >with?  Data class?  Source class?  Reader?
>> >
>> >Thanks,
>> >-Steve
>> >
>> >
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