[Sidefx-houdini-list] Grouping Outside Faces

Edmond Earl Smith ees041000 at utdallas.edu
Thu Jan 3 13:48:24 EST 2008


Sure, no problem.  I need to texture the faces pointing out with a 
different texture than the inner ones.  Just like bricks smashing with 
dirty outsides but clean inner brick textures that have not been 
exposed to the elements.  I need to do this procedurally.


Marc-Andre Carbonneau wrote:


>Hi Edmond,
>
>I am completely green to Houdini so I cannot help you but I am curious 
about why you want to make a selection of the inner faces. What are you 
going to do with it exactly? What are you trying to achieve?
>Thank for easing my curiosity! ;)
>
>Marc-Andre
>
>-----Original Message-----
>From: sidefx-houdini-list-bounces at sidefx.com 
[mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of Edmond 
Earl Smith
>Sent: January 3, 2008 1:13 PM
>To: sidefx-houdini-list at sidefx.com
>Subject: Re: [Sidefx-houdini-list] Grouping Outside Faces
>
>
>Hey thanks for the help.  I got something to work that's a little like 
>your suggestions.  I just had to do some fancy grouping.  One of the 
>bigger challenges is going to be getting this information to transfer 
>through DOPS and back into SOPS.  DOPS reassigns the RBD glued objects 
>so that each group is a separate RBD object.  When it does this it 
>reassigns the faces per object, so it's not like I can even create a 
>group and try and reference the faces later once they've been 
>simulated.  I have no clue how to grab these inner faces once the DOP 
>sim has gone through.  Any suggestions? 
>
>Thanks again so much,
>Eddie
>
>François Duchesneau wrote:
>
>
>>Ok, here's how to do it. Forget the first method because I thought the 
>>PolyExtrude would promote the points inside a group to the 
>corresponding 
>>extruded points. Anyway it's better the following way.
>>
>>For this, I assume your inner faces are all in pair of two because you 
>>want to have many cubes from the extruded grid.
>>
>>1-Create an other PolyExtude Sop but check "Remove Shared Sides" on 
>this 
>>one.
>>2-Append an AttribCreate after the second PolyExtrude and create a 
>>primitive attribute, let's say "inner" and set the value to 1.
>>3-Append an AttribTransfer after the first PolyExtrude and set the 
>>"Distance Threshold" to 0.001 for example.
>>4-Create a Group Sop with "Group by Expression" set to $INNER==0
>>
>>... and you're done. You can also look at an example file I've posted 
>on 
>>the Exchange called "Transparent Shattered Glass" that uses an other 
>>mechanism that put every coincident faces into a group without having 
>to 
>>duplicate the PolyExtrude.
>>
>>François
>>
>>François Duchesneau wrote:
>>> I'm sorry. I answered too quickly without cross-checking what I was 
>saiying.
>>>
>>> I think you'll have to do an intersection boolean operation with the 
>>> "extrudeSide" group from the PolyExtrude.
>>>
>>> I test that and let you know.
>>>
>>> François
>>>
>>> François Duchesneau wrote:
>>>   
>>>> You can append a Group Sop before the extrude, set the type to "Point" 
>>>> and go in the "edge" tab and check "Unshared Edges". This creates a 
>>>> group of all points being the boundary. Invert the group with a 
>boolean 
>>>> operation inside that Group Sop to get all points that are not a 
>boundary.
>>>>
>>>> All the edges in that group will be included inside the geometry after 
>>>> the extrude.
>>>>
>>>> François
>>>>
>>>>
>>>> Edmond Earl Smith wrote:
>>>>   
>>>>     
>>>>> Hello everyone, I have a fractured object that I create by extruding a 
>>>>> grid and partitioning the pieces.  I would like to group just the 
>faces 
>>>>> that are "inside" the object.  Much like the group extrudeSide when 
>you 
>>>>> use the polyextrude but without the outer faces, just the inner ones.
>>>>>
>>>>> thanks,
>>>>> Eddie
>>>>> _______________________________________________
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>>>>>
>>>>>   
>>>>>     
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