[vtkusers] How to project a curve onto surface

[Dženan Zukić]

You can discretize straight line segments into arbitrarily small pieces and
project them onto the surface.

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On Sat, Nov 30, 2013 at 6:06 AM, Green Hedgehog <yy198903 at 163.com> wrote:

> Dear Dženan Zukić,
> Thanks a lot for your reply. The key point is, how to connnect the
> projected points. I mean, how to guarantee the short lines connecting
> projected points lying on the surface?
>
>
>
>
>
>
> At 2013-11-29 19:15:56,"Dženan Zukić [via VTK]" <[hidden email]<http://user/SendEmail.jtp?type=node&node=5724732&i=0>>
> wrote:
>
> If your curve is a loop, you might want to do spherical projection.
> Determine center of area of the curve. Then go through all the points in
> your curve, for each cast a ray from center towards it, calculate
> intersection of this ray with the surface and place the projected point on
> this intersection. Lastly connect the projected points.
>
> In case your curve and the surface are not concentric, you might want to
> place the center of projection somewhere between them so the projection
> ends up on the surface.
>
>
> On Thu, Nov 28, 2013 at 1:24 PM, Green Hedgehog <[hidden email]<http://user/SendEmail.jtp?type=node&node=5724721&i=0>
> > wrote:
>
>> Dear Kenneth,
>> Thanks a lot for your reply. I think I didn't describe the question
>> clearly.
>> a) The curve isn't planar. It isn't close to planar neither. It is a
>> loop, an output of vtkSplineFilter.
>> b) The surface isn't close to planar near the curve.
>> c) I didn't get you quite well about this point. I mean I want the result
>> just looks like you draw the curve on the surface, that means after
>> projecting the result curve is totally *lying *on the surface. It
>> needn't be accurate, just looks smooth.
>>
>> Regards,
>> Yue
>>
>>
>>
>>
>>
>>
>> At 2013-11-28 14:39:54,"Kenneth Sloan-3 [via VTK]" <[hidden email]<http://user/SendEmail.jtp?type=node&node=5724694&i=0>>
>> wrote:
>>
>> A lot depends on the nature of the curve and the surface.
>>
>> a) is the curve (close to) planar?
>> b) is the surface close to planar near the curve?
>> c) do you want the curve literally "projected" onto the surface, or do
>> want
>>    the curve somehow "draped" over the surface?
>>
>> Easiest is probably the case where the surface is large and locally
>> "flat" near the curve, and the curve
>> itself is relatively flat.  Select a compromise plane (or, from another
>> point of view, a compromise vector from the curve in the direction of the
>> surface).  Sample the curve, and cast rays from curve sample points in the
>> direction of the surface.  Find points of intersection and connect the
>> dots.
>>
>> If both the surface and the curve are convoluted, then the problem
>> becomes much harder, and the answer less well defined.
>>
>> Good luck!
>> --
>> Kenneth Sloan
>> [hidden email] <http://user/SendEmail.jtp?type=node&node=5724691&i=0>
>>
>>
>> On Nov 28, 2013, at 05:49 , Green Hedgehog <[hidden email]<http://user/SendEmail.jtp?type=node&node=5724691&i=1>>
>> wrote:
>>
>> > Dear all,
>> >
>> > There is a closed surface with a curve near it. I want to project the
>> curve
>> > onto the surface and then render . Does anyone have any suggestions?
>> >
>> > Yue
>> >
>> >
>> >
>> > --
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