[Bf-committers] Inverse Shrinkwrap? (only "keep above surface")

[Tobias Oelgarte]

If you reduce the "offset" to 0.0 then the problem is not visible. It 
only happens with offset different from 0. Offset is ignored, until 
original mesh, without offset, is reached.

Am 19.02.2011 14:24, schrieb Tobias Oelgarte:
> Currently i did some tests and it shows that the behavior of 
> projection and  and nearest surface point is way different. Projection 
> also makes the vertices jumping. I tested it with svn rev34989 and 
> appended an very simple example. Just use the shapekey-slider (Key 1) 
> of the red inner object (something like a muscle) and you will see 
> that the skin is snapping. First nothing, then a jump, followed by a 
> smooth further transition. That is unacceptable for muscles and in 
> many complex cases even worse.
>
> Example file: http://www.pasteall.org/blend/5290
>
> Am 19.02.2011 10:16, schrieb Campbell Barton:
>> Found this can be done already (sort of),
>> Project negative then cull front or back.
>>
>> There was a bug where rotating the object made culling fail, fixed 
>> r34986.
>>
>> This works ok with a sphere/cube and sphere/plane so in real usage
>> there may be some other options needed.
>> If this isn't working well I'd be interested to see an example blend 
>> file.
>>
>> On Fri, Feb 18, 2011 at 8:02 PM, Daniel Salazar - 3Developer.com
>> <zanqdo at gmail.com>  wrote:
>>> Thumbs up for suggestion. For group behavior lets just wait for nodal
>>> modifiers, this will be a no brainer with a forgroup loop node
>>>
>>> cheers
>>>
>>> Daniel Salazar
>>>
>>>
>>> 2011/2/18<raulf at info.upr.edu.cu>:
>>>> Hi
>>>>
>>>> May be my recent released relaxation patch can help
>>>> http://www.box.net/shared/ddhtfnsq75
>>>>
>>>>
>>>>> HI guys!
>>>>>
>>>>> As I see it, shrinkwrap is lacking of two things that would make 
>>>>> it even
>>>>> better.
>>>>>
>>>>> 1_ A Neighboring vertexes smoothing factor. This would be done by 
>>>>> applying
>>>>> a kind of falloff to the affected surface like in these examples:
>>>>>
>>>>>   http://chrisevans3d.com/tutorials/maya_muscle.htm
>>>>>
>>>>> 2_ An algorithm that determines that if a vertex movement goes out 
>>>>> of a
>>>>> certain distance range, those vertexes should be smooth out or its
>>>>> movement averaged with the movement of the neighboring vertexes. This
>>>>> feature could avoid vertex artifacts with an articulated object, 
>>>>> specially
>>>>> in projection mode.
>>>>>
>>>>> Maybe this is too much to ask from Campbell's weekend quick fix, 
>>>>> but you
>>>>> never know when Jaguarandi is reading :p
>>>>>
>>>>>
>>>>>> Date: Fri, 18 Feb 2011 14:26:55 +0100
>>>>>> From: tobias.oelgarte at googlemail.com
>>>>>> To: bf-committers at blender.org
>>>>>> Subject: Re: [Bf-committers] Inverse Shrinkwrap? (only "keep above
>>>>>> surface")
>>>>>>
>>>>>> Using a group of objects could be useful, but if it's not done for
>>>>>> multiple objects, you still can just apply multiple shrinkwraps 
>>>>>> in "keep
>>>>>> above only" mode to achieve more or less the same result. In many 
>>>>>> cases
>>>>>> it would be just one "collision" object and fine. Of course 
>>>>>> groups of
>>>>>> objects would move the vertices more correctly. But as you said: One
>>>>>> step at a time. The first one alone would already be great.
>>>>>>
>>>>>> Am 18.02.2011 14:14, schrieb Campbell Barton:
>>>>>>> You're right that this is simple to add and agree it seems very
>>>>>> useful,
>>>>>>> quick way to reducing intersections without physics errors.
>>>>>>> The main downside I can see, as the verts slide over large 
>>>>>>> variance it
>>>>>>> could give visible popping in some cases, though this is no 
>>>>>>> difference
>>>>>>> then shrink-wrap for other uses.
>>>>>>>
>>>>>>> Though it makes me think for this feature it would be even more 
>>>>>>> useful
>>>>>>> in production is if the modifier could select a group of objects to
>>>>>>> 'not pass through', rather then a single one.
>>>>>>>
>>>>>>> But one thing at a time, this seems reasonable and if theres no
>>>>>>> objections I can add this over the weekend since I made some 
>>>>>>> changes
>>>>>>> to this area recently.
>>>>>>>
>>>>>>> On Fri, Feb 18, 2011 at 12:43 PM, Tobias Oelgarte
>>>>>>> <tobias.oelgarte at googlemail.com>    wrote:
>>>>>>>> Shrinkwrap is designed to force vertices onto the surface of 
>>>>>>>> another
>>>>>>>> object. In Nearest Surfacepoint mode it moves vertices either 
>>>>>>>> to the
>>>>>>>> surface or optionally let it also move outward until they are 
>>>>>>>> on the
>>>>>>>> surface. So you can work with essential two options. But 
>>>>>>>> wouldn't it
>>>>>>>> make more sense to include also the possibility that vertices can
>>>>>> also
>>>>>>>> only be moved up onto the surface and and not moved toward it?
>>>>>>>>
>>>>>>>> It would allow you to throw a ball against a window, making the
>>>>>> vertices
>>>>>>>> stop that would pass trough it. There are many possible usages i
>>>>>> could
>>>>>>>> think of: Bubbles in a glass. Shoes that not sink slightly into 
>>>>>>>> the
>>>>>>>> ground. Body parts that "collide" with each other, and many more.
>>>>>>>>
>>>>>>>> Since the algorithm seams to handle this case already -- 
>>>>>>>> knowing if a
>>>>>>>> vertex is inside or outside the target, for "Keep above 
>>>>>>>> surface"  --
>>>>>> it
>>>>>>>> should be just an additional option. Am i right?
>>>>>>>>
>>>>>>>> Cases (now):
>>>>>>>> * Shrink to Surface
>>>>>>>> * Shrink to Surface and move outward for "keep above"
>>>>>>>>
>>>>>>>> Cases (desired):
>>>>>>>> * Shrink to Surface
>>>>>>>> * Only "keep above"
>>>>>>>> * Shrink to Surface and move outward for "keep above"
>>>>>>>>
>>>>>>>> Hope this is a little inspiration. It would make shrinkwrap 
>>>>>>>> much more
>>>>>>>> awesome.
>>>>>>>>
>>>>>>>> Greetings from
>>>>>>>> Tobias Oelgarte
>>>>>>>> _______________________________________________
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>>>>>>>> Bf-committers at blender.org
>>>>>>>> http://lists.blender.org/mailman/listinfo/bf-committers
>>>>>>>>
>>>>>>>
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