[vtk-developers] Class design for spline visualizations

Lin M majcjc at gmail.com
Wed Jun 3 18:52:31 EDT 2015 

Hi Dr. Thompson,

I have added helper functions for ellipse and hyperbola to generate control
points for these curves.
The NURBS book gives a 2-d bezier interpolation case which is a cylinder
and I will added this to the current test soon.

Best,
Lin

On Wed, Jun 3, 2015 at 9:25 AM, Lin M <majcjc at gmail.com> wrote:

> Hi Dr. Thompson,
>
> Is there any example for 2- and 3-d Bezier Interpolation?
>
> Best,
> Lin
>
> On Sat, May 30, 2015 at 1:54 PM, Lin M <majcjc at gmail.com> wrote:
>
>> Hi Dr. Thompson,
>>
>> I have written a helper function to generate control points for arbitrary
>> ellipse and modified the PatchInterpolation.py test to image test which
>> contains line, circle and ellipse.
>>
>> A question about the push the data. I followed the instruction in
>> https://gitlab.kitware.com/vtk/vtk/blob/master/Documentation/dev/git/data.md,
>> but I didn't see the message when doing the commit step.
>>
>> Some/Module/Testing/Data/Baseline/MyTest.png.md5: Added content to Git at refs/data/MD5/...
>> Some/Module/Testing/Data/Baseline/MyTest.png.md5: Added content to local store at .ExternalData/MD5/...
>> Content link Some/Module/Testing/Data/Baseline/MyTest.png.md5 -> .ExternalData/MD5/...
>>
>> The image test runs correctly in my local machine.
>>
>> Best,
>> Lin
>>
>> On Sat, May 23, 2015 at 12:16 AM, David Thompson <
>> david.thompson at kitware.com> wrote:
>>
>>> Hi Lin,
>>>
>>> I believe VTK expects each test to generate a single baseline image
>>> whose filename matches the Python script name (e.g.,
>>> TestSynchronizedTemplates3D.py
>>> <https://gitlab.kitware.com/vtk/vtk/blob/master/Filters/Core/Testing/Python/TestSynchronizedTemplates3D.py> must
>>> have its baseline image named TestSynchronizedTemplates3D.
>>> <https://gitlab.kitware.com/vtk/vtk/blob/master/Filters/Core/Testing/Python/TestSynchronizedTemplates3D.py>png
>>> in the Data/Baselines directory).
>>>
>>>     David
>>>
>>> On May 22, 2015, at 23:15, Lin M <majcjc at gmail.com> wrote:
>>>
>>> Hi Dr. Thompson
>>>
>>> I changed the python test to baseline image and followed the
>>> instructions in the VTK Data page, but running CMake doesn't seem to make
>>> the .md5 files. Do you have any idea about that?
>>>
>>> I outputed two images named bezier-circle.png and bezier-line.png and
>>> put them in source-tree/Filters/Bezier/Testing/Data/Baseline.
>>>
>>> Best,
>>> Lin
>>>
>>>
>>> On Tue, May 19, 2015 at 1:52 PM, David Thompson <
>>> david.thompson at kitware.com> wrote:
>>>
>>>> Hi Lin,
>>>>
>>>> A few additional things that might help:
>>>>
>>>> 1. When you are done reviewing the merge request I assigned to you,
>>>> please click "Accept merge request" or add a "+1" comment so that it will
>>>> become part of the splines/filter-bezier branch.
>>>>
>>>> 2. A good pattern to follow for the image-based test is
>>>> Filters/Sources/Testing/Python/TestPlatonicSolids.py . You can see how it
>>>> obtains the path to img_file and calls vtk.test.Testing.compareImage to
>>>> perform a rendering to compare. The baseline image that the rendering is
>>>> compared against is not stored in the VTK git repo. Instead, MD5 checksums
>>>> of images are stored in the git repo and the images are uploaded
>>>> separately. See
>>>>
>>>>
>>>> https://gitlab.kitware.com/vtk/vtk/blob/master/Documentation/dev/git/data.md
>>>>
>>>> for a description of how to generate a test image, add its MD5 sum, and
>>>> upload it with your merge request.
>>>>
>>>> 3. If you are going to generate helper methods to create conic
>>>> sections, then be aware that you'll have to return multiple sets of control
>>>> points because ellipses cannot be represented with a single patch (it is
>>>> best to return one patch per quadrant) because of the way they are
>>>> parameterized.
>>>>
>>>>         David
>>>>
>>>> > On May 18, 2015, at 10:45 PM, Lin M <majcjc at gmail.com> wrote:
>>>> >
>>>> > Hi Dr. Thompson
>>>> >
>>>> > Thanks! I'll look into that and implement the test asap.
>>>> >
>>>> > Best,
>>>> > Lin
>>>> >
>>>> > On Mon, May 18, 2015 at 10:36 PM, David Thompson <
>>>> david.thompson at kitware.com> wrote:
>>>> > Hi Lin,
>>>> >
>>>> > Sorry for the slow reply.
>>>> >
>>>> > > Is there any dataset for precomputed Bezier interpolation? I'm
>>>> currently comparing the result with my manual calculating. In this way I
>>>> can not test many examples and it's quite low efficient.
>>>> >
>>>> > I've pushed a merge request to the project that adds a couple simple
>>>> test cases. I'll add some more over the next few days. You can run the test
>>>> by building VTK with the VTK_WRAP_PYTHON option turned ON and then running:
>>>> >
>>>> >     make
>>>> >     ./bin/vtkpython
>>>> /path/to/src/Filters/Bezier/Testing/Python/PatchInterpolation.py
>>>> >
>>>> > If you uncomment the lines below the "For debugging, ..." message in
>>>> PatchInterpolation.py, running the test will create some files (named
>>>> bezier-circle.vtk and bezier-line.vtk) that you can load into ParaView.
>>>> >
>>>> > 1. As I mentioned earlier, it would be great to do image-based
>>>> testing. A good exercise would be to modify the Python test into an image
>>>> test version.
>>>> >
>>>> > 2. Another good exercise would be to generate control points for
>>>> other conic sections such as hyperbolas, parabolas, and the more generate
>>>> case of ellipses. I recommend "The NURBS Book" by Les Piegl; the circle
>>>> quadrant example in the Python test is from pp. 26--32 of the book. It
>>>> would be really nice to have a utility that would create control points
>>>> given a few shape parameters. For example:
>>>> >
>>>> >     ctrlPts, prange = ellipse(major_radius=2, minor_radius=1)
>>>> >     ctrlPts, prange = hyperbola(semi_major_axis=2/3, eccentricity=1)
>>>> >
>>>> > Once we have the 1-, 2-, and 3-d Bezier interpolation tested, we can
>>>> work on converting B-splines into Bézier patches and testing that.
>>>> >
>>>> >         David
>>>> >
>>>> > >
>>>> > > On Mon, Apr 27, 2015 at 1:46 PM, David Thompson <
>>>> david.thompson at kitware.com> wrote:
>>>> > > Hi Lin,
>>>> > >
>>>> > > > ... I changed the method to compute binomial coefficient from
>>>> vtkMath::Binomial to vtkMath::Factorial using our memoization improvement
>>>> and tried to merge from Lin.Ma/filter-bezier to Spline/filter-bezier.
>>>> > >
>>>> > > Great! I can see that you were able to merge to the branch.
>>>> > >
>>>> > > > What do you think is the proper thing to do next?
>>>> > >
>>>> > > Right now, it looks like TestPatchInterpolation is modifying the
>>>> array holding control point coordinates. I think it would be a good idea to
>>>> write the interpolated points to a separate array and then make the test
>>>> verify that Bernstein polynomial is being computed properly.
>>>> > >
>>>> > > There are 2 ways to verify things: value tests and image tests.
>>>> > >
>>>> > > 1. Value testing. Interpolate a few different r values on a few
>>>> different sets of control points and compare the resulting point
>>>> coordinates to values you know are good. The comparison must allow for
>>>> small differences due to the differences in floating-point arithmetic
>>>> implementations on different platforms.
>>>> > >
>>>> > > 2. Image testing. Plot the interpolated points and compare the
>>>> rendering of the interpolated points to one you have verified is correct.
>>>> While not as accurate as value testing, it can often be easier to debug a
>>>> failing test with a rendered image. VTK provides utilities for comparing
>>>> images (also allowing for small differences due to floating-point math,
>>>> OpenGL implementations, and so on). The image baselines that get compared
>>>> to your test's rendering are stored outside of the git repository to keep
>>>> the repository from getting bloated. Instead, the MD5 sum of the baseline
>>>> images are stored in the git repository and the images are stored
>>>> separately on Kitware's servers, which can be queried to find a file with a
>>>> given MD5 sum.
>>>> > >
>>>> > > Please take a look at this documentation on adding test data and
>>>> baseline images to VTK:
>>>> > >
>>>> > >
>>>> https://gitlab.kitware.com/vtk/vtk/blob/master/Documentation/dev/git/data.md
>>>> > >
>>>> > > and see if you can add an image-based test of the patch
>>>> interpolation.
>>>> > >
>>>> > >         David
>>>> > >
>>>> >
>>>> >
>>>>
>>>>
>>>
>>
>
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