[vtk-developers] Triangular patch interpolation

[Lin M]

Hi Dr. Thompson,

I have found some surfaces model in brep format from
http://www.opencascade.org/showroom/shapegallery/gal5/ and I think the
motorcycle is correct. The reason why it looks odd in the seat area is
because those surfaces need some bool operation which we haven't
implemented yet.

I try to load the model of suitcase, boat and F1 and all of them displayed
correctly, I suppose. :-)

P.S.

Best,
Lin

On Sat, Aug 15, 2015 at 2:45 PM, Lin M <majcjc at gmail.com> wrote:

> Hi Dr. Thompson,
>
> I finally make the vtkBrepReader work (partially, it can only load surface
> patches). The problem is that I can not find enough data source. None of
> the files in CGM/test contains nurbs surface and the only one with Bezier
> surface is moto.brep. It looks like this
> As you can see, the seats area looks strange in the rendered shape. So I
> really need some mroe simpler nurbs shape to test my implementation. Can
> you give some advice where I should look for? Thanks!
>
> Best,
> Lin
> ​
>
>
> On Wed, Aug 12, 2015 at 11:07 PM, <majcjc at gmail.com> wrote:
>
>> Thank you for your suggestions!
>>
>> I will polish the code and make them throughly tested before merged to
>> VTK.
>>
>> Best,
>> Lin
>>
>>
>>
>> On Wed, Aug 12, 2015 at 7:48 AM -0700, "David Thompson" <
>> david.thompson at kitware.com> wrote:
>>
>> Hi Lin,
>>
>> > I have finished the point inversion and projection algorithm for both
>> 1-d, 2-d and 3-d NURBS.
>> > We can turn to more dedicated algorithms now.
>>
>> I think that a better use of the remaining time would be to clean up and
>> merge your work into VTK. You have made great progress and it looks really
>> good. It would be better to polish it so it is easy to maintain and get it
>> accepted than to push for contouring and be left with something that is not
>> tested well enough to be maintained as VTK changes. That way you or another
>> GSoC student can continue things next summer.
>>
>> It has been my experience that the only way to ensure it is maintained is
>> to make sure it is extensively tested so that when a change to VTK is
>> proposed, the developer making the change gets immediate feedback that the
>> change requires work on the spline classes. So, I propose doing the
>> following:
>>
>> 1. There are some style changes that need to be made. I'll push some
>> changes off your branch to sampling/vtk, but to get started:
>>    a. There is trailing whitespace at the ends of lines in many files
>> which are disallowed by our pre-merge scripts.
>>    b. Method names should be spelled out, so "Curv," "Surf," and "Volm"
>> should become "Curve," "Surface," and "Volume." I know it is nice for names
>> to have the same length, but it is nicer for other developers to be able to
>> predict the names of methods across the entire toolkit. :-)
>>
>> 2. Testing should be more exhaustive testing to make sure that changes to
>> VTK don't break things. Right now only interpolation is tested at all (and
>> there is a lot of commented-out code in that test which should probably be
>> removed). Other tests should include, for example,
>>   a. simplicial (triangular and tetrahedral) patch interpolation (you can
>> do this with an image-based test and/or by checking that numeric values are
>> within a tolerance of an analytical solution,
>>   b. point inversion for rectangular and simplicial patches
>>   c. derivative computation
>>   d. the NURBS adaptor should be tested with several shapes whose patches
>> can be computed
>>
>> 3. Every class should have documentation that covers its purpose, its
>> intended lifecycle (how should it be used, what methods must be called
>> before others, etc.). The way field data is used to hold NURBS knot vectors
>> should be documented and should have an example data file (which should be
>> used in an image test to verify that it continues to work).
>>
>>         Thanks,
>>         David
>>
>> > On Sun, Aug 9, 2015 at 2:47 PM, Lin M <majcjc at gmail.com> wrote:
>> > Hi Dr. Thompson,
>> >
>> > I have pushed new methods to compute point inversion and projection to
>> gitlab.
>> > It took longer time than I expected. It would be really helpful if you
>> could review the code a little bit. Thanks!
>> >
>> > Best,
>> > Lin
>> >
>> > On Mon, Aug 3, 2015 at 10:50 AM, David Thompson <
>> david.thompson at kitware.com> wrote:
>> > Hi Lin,
>> >
>> > Yes, that is correct. Inserting knot values does not change the
>> polynomial degree or shape, it just adds control points so that the weights
>> are uniform (as required by the Bézier basis). So, the underlying
>> parameterization is unchanged... it just has more piecewise segments.
>> >
>> >     David
>> >
>> >
>> >
>> > On Aug 2, 2015, at 22:38, Lin M <majcjc at gmail.com> wrote:
>> >
>> >> Hi Dr. Thompson,
>> >>
>> >> I have a question about the inversion and projection. Currently, we
>> evaluate the NURBS by inserting knots and making it into Bezier forms. My
>> question is that if I evaluate u = 0.2 in original knot vector [0,1,2,3],
>> would it be the same to evaluate u = 0.2 in the new knot vector which is a
>> bezier form?
>> >>
>> >> Best,
>> >> Lin
>> >>
>> >> On Mon, Jul 27, 2015 at 1:26 AM, Lin M <majcjc at gmail.com> wrote:
>> >> Hi Dr. Thompson,
>> >>
>> >> I have added new method
>> vtkPatachInterpolation::InterpolateOnSimplicialPatch() and pushed to gitlab.
>> >>
>> >> I'm now working on the point inversion part.
>> >>
>> >> Best,
>> >> Lin
>> >>
>> >> On Sun, Jul 26, 2015 at 8:05 PM, David Thompson <
>> david.thompson at kitware.com> wrote:
>> >> Hi Lin,
>> >>
>> >> How is triangular/tetrahedral patch interpolation going? They will be
>> a basic building block of the contouring and cutting algorithms. By
>> identifying points on edges, edges on surfaces, and surfaces in volumes
>> that take on a single value, a single patch can be decomposed into sections
>> that are inside, outside, or on an isosurface. Not all of these pieces can
>> be expressed as brick patches, but they can be expressed as simplicial
>> patches.
>> >>
>> >>     David
>> >>
>> >>
>> >
>> >
>>
>>
>
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