[Insight-users] IsInside test TubeSpatialObject

[Dan Mueller]

Hi Julien and Jerome,

The test file attached to bug-3418 
(http://www.itk.org/Bug/bug.php?op=show&bugid=3418&pos=0) is an example 
of when lambda is negative for flat end-types. I have verified this by 
putting a conditional std::cout statement in 
itkTubeSpatialObject::IsInside(.) and ran the 
itk::SpatialObjectToImageFilter with the attached file. FYI this 
SpatialObject should have the following specifcations: size=[64, 64, 
64], spacing=[1, 1, 1], and offset = [0, 0, 0].

Having a quick look at the code, if the point being tested (ie. 
transformedPoint) is ever less than a (the first iterator) then A will 
be negative, which in turn means lambda would be negative. Doesn't this 
occur for all points on the "left" of the tube?

Honestly, I haven't looked too much into the guts of 
itkTubeSpatialObject::IsInside(.) (except to report the original bug) - 
but the code works fine for me now. Jerome: if your interest is in 
speeding up SpatialObject to Image conversion, I hope to submit an 
article to the InsightJournal within the next few weeks with one such 
proposal (not requiring any changes to existing code)...

Hope this helps.

Cheers

Dan


Julien Jomier wrote:
> Hi Jerome,
>
> I think you are right. The test for negative Lambda is incorrect for a 
> flat end-type.
> I've CC Dan Mueller who reported the bug for negative lambda. He might 
> have some suggestions on this topic. Dan, if you agree that if lambda 
> is negative we should skip the pair of points, I will commit a fix.
>
> Thanks for looking into this,
>
> Julien
>
> SCHMID, Jerome wrote:
>> Hi All,
>>
>>  
>>
>> I have a pb to understand the lambda condition being negative in the 
>> IsInside( point ) of TubeSpatialObject.
>>
>>  
>>
>> To me if lambda is negative, the current 2 consecutive points used 
>> for the test are not relevant, we should skip them and look for the 
>> next pair. Lambda negative means that the point is not inside the 
>> space within the two « normal disc » of the two points, so why do 
>> some test ?
>>
>> I really cannot understand the test done on negative lambda. A bug on 
>> the bug tracker dealing with negative lambda was corrected suggesting 
>> that this lambda <0 test was genuine….
>>
>>  
>>
>> Can somebody provide me a very simple figure where this test is 
>> relevant? An mhd file with a point to test would be okay.
>>
>>  
>>
>> Thanks !
>>
>>  
>>
>> /Best Regards,/
>>
>> / /
>>
>> /Jerome Schmid/
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Insight-users mailing list
>> Insight-users at itk.org
>> http://www.itk.org/mailman/listinfo/insight-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://public.kitware.com/pipermail/insight-users/attachments/20060719/5f5ca9b2/attachment.htm