[Sidefx-houdini-list] Surface from image stack

François Duchesneau sidefx at trinix.ca
Thu Feb 11 17:16:29 EST 2010


That reminds me a tool I created to mimick Blast Code. In Blast Code you 
could use a bad quality crack pattern found on the web with varying line 
thickness. The tool I created used the Trace Sop internally but had to 
do lots of Sop operation to make it work. However, it was very picky 
about the line width. I'd be curious to know what is the algorithm Blast 
Code uses because it looks more like something giving the center of the 
line only, like you want. That little improvement on the Trace Sop would 
be great.

François

Michael K. O'Brien wrote:
> Hola~
>
>   
>> -- On Thu, Feb 11, 2010 at 04:29:58PM -0500, Jerry wrote:
>> Check the second tab on the trace SOP.
>>     
>
> I tried that, but without any luck. I'll give it another go.
>
> My sample image is 16x16, all black, white horiz line in the middle. I end up
> with with a closed curve that encircles all of the pixels.
>
> I ended up writing a medial axis node, which is really slow, but seems to be a
> bit closer to what I would expect.
>
> MO
>
>   
>>> Hola~
>>>
>>>       
>>>> -- On Thu, Feb 11, 2010 at 03:19:05PM -0500, Mark Elendt wrote:
>>>> On Thursday Feb 11 at 14:46, Mark Bolstad wrote:
>>>>         
>>>>> I have a stack of black and white images that consist of a set of
>>>>> disconnected circle like shapes. First, how do you extract the  
>>>>>           
>>>> boundary
>>>>         
>>>>> curve(s) and pass them to a SOP?
>>>>>
>>>>> Second, given a set of these extracted curves, I need to join them  
>>>>>           
>>>> into a
>>>>         
>>>>> surface (assume some fixed offset between the curves). The problem is  
>>>>>           
>>>> that
>>>>         
>>>>> in some cases I'll have two curves on one level and 1 curve on the  
>>>>>           
>>>> next
>>>>         
>>>>> level (the actual data is bifurcating somewhere in between the  
>>>>>           
>>>> levels).
>>>>         
>>>>> The application is reconstructing neurons from a set of electron  
>>>>>           
>>>> microscopy
>>>>         
>>>>> images.
>>>>>
>>>>> Any help is appreciated.
>>>>>           
>>>> Could you make a volume (even an i3d file)?
>>>> The ISO SOP with an inside/out expression?
>>>>
>>>> If the topology changes (i.e. you have two circles blending to one),
>>>> that could be problematic.
>>>>
>>>> If you are guaranteed to have only one circle, then use the trace SOP
>>>> and poly loft (or poly spline and skin).
>>>>         
>>> Is there a way to get a true curve out of trace? Trace wants to surround  
>>> each
>>> pixel with a poly face, as opposed to generating a curve that connects  
>>> the
>>> pixels above the threshold, right?
>>>
>>> MO
>>>
>>>       
>>>> --
>>>> Mark Elendt
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>>>>         
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>
>   



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