[Bf-committers] lattice spline interpolation

[Nicholas Rishel]

David,

The Wiki section on submitting patches might be of assistance:
http://wiki.blender.org/index.php/Dev:Doc/Process/Patches#Submitting_Patches

Nick


On Tue, Jun 18, 2013 at 4:27 PM, <dlr13 at me.com> wrote:

> Hello again.  I am hoping to get a response this time now that things seem
> to have quieted down some on the list.  I've got a patch that modifies the
> lattice deformer ever so slightly...it simply adds a new spline option.
>  More info is below.  this is a very minor change and I hope it can be
> accepted and integrated quickly. We are using Blender at NASA Ames as an
> engineering tool, something many of you may never have expected. However,
> the lattice deformer is great for doing shape optimization on triangulated
> surfaces of airplanes and other aerospace geometries.  currently I am using
> Blender to do aerostructural analysis, where we predict the deflection of
> flexible wings under aerodynamic load (see 787) and actually apply the
> deflection via Blender.  However, the splines available in the lattice
> deformer are inadequate as coded for our use, so I added a new spline...the
> Catmull-Rom spline..which is the same as what Blender uses for animation.
>  this does not remove or alter an
>  y previous features, it simply adds a another option.
>
> To whom should I speak about patch files?  Thanks.
>
>
> _____
> David
>
>
>
>
> On May 1, 2013, at 3:12 PM, dlr13 at me.com wrote:
>
> > Hi all.  I discussed updating the lattice spline a few months ago.  I
> have since done some more research and would like to propose a very simple
> improvement to the lattice deformer.  The current options are "Linear",
> "Cardinal", and "Bspline".  The Cardinal spline is set to a tension of 0.71
> which can produce very wavy results when the lattice is dense.  However, if
> we changed the tension to 0.5, the spline becomes the popular Catmull-Rom
> spline and produces very nice results, results we can use here at NASA Ames
> to deform wings.  The Catmull-Rom spline is already being used in other
> parts of Blender, so it's natural to include it as an option in the lattice.
> >
> > The changes to the code are extremely minor...3-4 source files.  1-2
> lines in most cases, and only 12 or so more in one file with code that
> looks very similar to what is already there.  I can put together the patch
> in about an hour.
> >
> > My proposal is this:
> >
> > Add "Catmull-Rom" as an option for the spline interpolators in the
> lattice deformer.
> >
> >
> > That's it.  Quick and simple.  Doesn't alter any current functionality,
> it simply expands the current number of options from 3 to 4.
> >
> > Can such a project be approved?  Thanks.
> >
> >
> >
> > _____
> > David
> >
> >
> >
> >
> > On Feb 12, 2013, at 3:11 AM, Ton Roosendaal <ton at blender.org> wrote:
> >
> >> Hi,
> >>
> >> This code and the formula is like 18 years old, i'd welcome someone
> checking on improvements. Rather to make it really good, not just with a
> button to set the interplation value.
> >>
> >> Your 'plot' didnt get through...
> >>
> >> -Ton-
> >>
> >> ------------------------------------------------------------------------
> >> Ton Roosendaal  Blender Foundation   ton at blender.org    www.blender.org
> >> Blender Institute   Entrepotdok 57A  1018AD Amsterdam   The Netherlands
> >>
> >> On 11 Feb, 2013, at 23:26, dlr13 at mac.com wrote:
> >>
> >>> Pardon me if this is the wrong list to send this to.  If so, I would
> appreciate someone pointing me in the right direction.  Thanks!
> >>>
> >>>
> >>> The Cardinal spline interpolation for lattices befuddles me. The
> tension-like variable (fc in the code) is set to 0.71, which I'm guessing
> is approximately 1/sqrt(2).  However, this gives very ugly and wavy results
> on long straight objects like an airplane wing. In fact, the slopes at the
> knots is just plain wrong.  However, when fc = 0.5, I get very nice
> cubic-spline-like behavior except at the end points where the code logic
> just seems to be wrong.  Nevertheless, the waviness at the knots is
> disconcerting in the current distribution of Blender. The plots below show
> what I mean.
> >>>
> >>>
> >>>
> >>>
> >>> Thoughts?  Any chance that fc (tension?) variable can be a parameter
> the user could control?
> >>>
> >>>
> >>> _____
> >>> David
> >>>
> >>>
> >>>
> >>>
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>
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