[Sidefx-houdini-list] Point clouds

Andy Nicholas andy at andynicholas.com
Thu Apr 2 12:49:39 EDT 2009


Ah, okay. That's good to know, thanks Spencer.

A


> when using PC in in Shaders you cannot use the op: syntax.  You have to
> write out your pts as either .pc/.bgeo files.
>
> ----- Original Message -----
> From: "Andy Nicholas" <andy at andynicholas.com>
> To: sidefx-houdini-list at sidefx.com
> Sent: Thursday, 2 April, 2009 12:06:46 GMT -05:00 US/Canada Eastern
> Subject: Re: [Sidefx-houdini-list] Point clouds
>
> 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.
>
> Cheers
>
> Andy
>
>
>
>>> 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
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Sidefx-houdini-list mailing list
>>>>>>> Sidefx-houdini-list at sidefx.com
>>>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>
>>
>>
>
>
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> Spencer Lueders
> Technical Director
> Framestore NY
>





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