[Sidefx-houdini-list] Point clouds

Andy Nicholas andy at andynicholas.com
Thu Apr 2 12:06:46 EDT 2009

That's cool, thanks a lot François. Yep, I changed the channel from
".distance" to ".number" and fed that into a random color network to
produce the Voronoi. It works a treat.

BTW, the only thing that I've still not got working is using the "op:"
syntax for the file parameter. When I point the pcopen VOP at the scatter
SOP output using "op:/obj/geo1/OUT_PC", it doesn't work. I get some error
saying "Unable to get VEX context from: op:/obj/geo1/OUT_PC". Do you
happen to know what the problem might be?

I just noticed your addition to the help docs, so thanks for that too.



>> I decided I should put more kind of examples before posting that to the
>> Exchange.
>> Instead I put you in copy with the files attached. Maybe you were
>> missing the transform from current space to world space of P to the
>> pcopen function. I haven't included the loop, just reading the closest
>> point.
>> I wanted one day to try a real leather pattern where you have more
>> cracks around where the skin folds etc instead of a uniform voronoi
>> pattern. I think your idea to make it with a point cloud is very
>> promising. I'll try that soon. It's amazing the amount of stuff we can
>> do with point clouds. I love that!
>> François
>> François Duchesneau wrote:
>>> Every node should have at least one example file. I'll try to create
>>> something for you. Maybe I can post it on the Exchange.
>>> François
>>> Andy Nicholas wrote:
>>>> Hi François,
>>>> I had a look at the help cards for pcopen and pcfilter but they're
>>>> using
>>>> VEX code. I'm trying to get something to work with the VEX nodes. If I
>>>> hook up some nodes in a way that corresponds with the VEX code I get
>>>> nothing, even though the code generated by the VEX network looks
>>>> extremely
>>>> similar to the example VEX code. Maybe I'm doing something wrong, but
>>>> I
>>>> don't think so.
>>>> I do have a vague memory of seeing a post a while ago where the
>>>> pointcloud
>>>> VEX functions worked, but the corresponding VEX nodes don't. Is that
>>>> true?
>>>> Incidentally, there isn't any help provided for any of the VEX point
>>>> cloud
>>>> nodes. I know they're essentially the same, but without help cards for
>>>> them, we aren't going to get any example scene files either. I've
>>>> heard
>>>> great things about using point clouds and it'd be great to get some
>>>> better
>>>> documentation and example scenes for them.
>>>> Thanks for your help
>>>> Andy
>>>>> Usually what I do is look at the example in the help of pcopen or
>>>>> pcfilter and it gives you an example of how to open it and extract
>>>>> data
>>>>> out of it.
>>>>> In you case you will probably need "point.distance" keyword in
>>>>> pcimport.
>>>>> For the rest, you can create any point cloud with the Scatter Sop and
>>>>> write any custom attribute you want. I don't know if it's better to
>>>>> use
>>>>> a .pc format but I've always saved that to .bgeo and it works fine.
>>>>> Test it out with a simple shader that extract the distance and pipe
>>>>> it
>>>>> to Cf before going into the Voroinoi coding.
>>>>> François
>>>>> Andy Nicholas wrote:
>>>>>> Hi,
>>>>>> Can anyone help, I need to get get point clouds working with a
>>>>>> shader
>>>>>> but
>>>>>> so far I've been unable to make it work. All I want to do is to be
>>>>>> able
>>>>>> to
>>>>>> create a Voronoi cell type pattern based on the point cloud. It
>>>>>> should
>>>>>> be
>>>>>> simple.
>>>>>> I had a look at the example on the Odforce Wiki, but it doesn't work
>>>>>> either. Does anyone know of a tutorial or example of a simple point
>>>>>> cloud
>>>>>> shader working?
>>>>>> Thanks a lot
>>>>>> Andy
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