[vtk-developers] vtkExplicitCell

[Will Schroeder]

This is very exciting. Thanks for the update. Once we can represent NURBS
properly we'll have to build a CAD modeller (just a few decades of work :-)
but boy would I like to have a nice, open modeller that interfaces into VTK
well).

W

On Fri, Jul 3, 2015 at 11:22 AM, David Thompson <david.thompson at kitware.com>
wrote:

> > This could work, although I'm not quite seeing how trim edges would fit
> in.
>
> All the trimming I've seen done in CAD BReps is in world coordinates with
> splined curves that represent the bounding edges of the surface, not in
> parameter space; meaning that the bounding curves would also exist in the
> multiblock of structured grids and could thus be referenced in a surface's
> field data (by block ID, for instance).
>
> I agree that we would have to figure something out if given a trim polygon
> in parameter-space coordinates. That doesn't seem like an insurmountable
> obstacle, though. And having a NURBS representation using standard VTK
> datasets with adaptor classes that provide access and convenience methods
> seems really desirable so that filters can be used on the control polygon
> point coordinates and point data (e.g., vtkArrayCalculator,
> vtkWarpScalars/Vectors).
>
> > Also sometimes there are supplemental structures like polygonal
> tessellations to help speed up geometric operations, etc.
>
> What Lin is working on now is generating those tessellations for
> rendering. Assuming we generate a multiblock of unstructured grid
> tessellations in the same tree structure, it could be used for both
> rendering and accelerating geometric operations.
>
>         David
>
> >
> > On Fri, Jul 3, 2015 at 9:15 AM, David Thompson <
> david.thompson at kitware.com> wrote:
> > > Long term I'd like to think how we could represent a CAD model with a
> large number of trimmed splines.
> >
> > What problem do you foresee with a multiblock of structured grids? The
> memory overhead of vtkStructuredGrid? It seems pretty minimal to me
> compared to the b-reps CAD packages use and the multiblock dataset need not
> be flat... it could be a bounding box hierarchy for fast culling of
> irrelevant patches.
> >
> >         David
> >
> >
> >
> > --
> > William J. Schroeder, PhD
> > Kitware, Inc.
> > 28 Corporate Drive
> > Clifton Park, NY 12065
> > will.schroeder at kitware.com
> > http://www.kitware.com
> > (518) 881-4902
>
>


-- 
William J. Schroeder, PhD
Kitware, Inc.
28 Corporate Drive
Clifton Park, NY 12065
will.schroeder at kitware.com
http://www.kitware.com
(518) 881-4902
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