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David Phillip Oster
Fri, Jun 7, 2024 6:32 PM

On Thu, Jun 6, 2024 at 3:28 PM William F. Adams via Discuss <
discuss@lists.openscad.org> wrote:

My thanks to everyone's input and thoughts.

It seems to me that for the three planes:

  • XY
  • XZ
  • ZY

it should be possible to have three Bézier curves (left-most/right-most
or front-back or top/bottom for two, and a mid-line for the third), so any
given region should be definable by:

3 * planes * 3 * Bézier curves * (2 on-curve points + 2 off-curve
points) == 36 coordinate pairs

which is a marked contrast to representations such as:

https://github.com/DavidPhillipOster/Teapot

Thanks for taking a look at my work.

I was surprised to find no instances of the Newell Teapot
https://en.wikipedia.org/wiki/Utah_teapot on thingiverse.

I took a 1986 publication of the Newell Teapot and ported it to OpenSCAD
with BOSL2. I cut the original in half by taking advantage of its symmetry
about the Y axis and using the OpenSCAD primitive: mirror.

Next steps for me is taking advantage of the radial symmetry of the lid and
body by using rotate_extrude to make manifold shapes of the teapot lid and
body.

bezier_vnf already works with a bezier patch defined as  16 control points,
or 48 floats, smaller than the 36 coordinate pairs (72 floats) you propose.
For a square patch, bezier_vnf works with just 4 control points. For a
planar patch, where the boundary is a cubic bezier, 8 control points it
interprets as two layers of 4 points each.

It would be nice if there were something like
https://github.com/butcherg/wxpolygon that worked with Apple Vision Pro
that let you work with 3D models in with your hands and eyes to reach into
the simulated 3D space and grab a control point to move it slightly in 3D
space, writing back to a prepared .scad file.

In the same way wxpolygon doesn't work with arbitrary .scad files but it
does let you work with its text files that are compatible with OpenSCAD.

On Thu, Jun 6, 2024 at 3:28 PM William F. Adams via Discuss < discuss@lists.openscad.org> wrote: > My thanks to everyone's input and thoughts. > … > It seems to me that for the three planes: > > - XY > - XZ > - ZY > > it should be possible to have three Bézier curves (left-most/right-most > or front-back or top/bottom for two, and a mid-line for the third), so any > given region should be definable by: > > 3 * planes * 3 * Bézier curves * (2 on-curve points + 2 off-curve > points) == 36 coordinate pairs > > which is a marked contrast to representations such as: > > https://github.com/DavidPhillipOster/Teapot > Thanks for taking a look at my work. I was surprised to find no instances of the Newell Teapot <https://en.wikipedia.org/wiki/Utah_teapot> on thingiverse. I took a 1986 publication of the Newell Teapot and ported it to OpenSCAD with BOSL2. I cut the original in half by taking advantage of its symmetry about the Y axis and using the OpenSCAD primitive: mirror. Next steps for me is taking advantage of the radial symmetry of the lid and body by using rotate_extrude to make manifold shapes of the teapot lid and body. bezier_vnf already works with a bezier patch defined as 16 control points, or 48 floats, smaller than the 36 coordinate pairs (72 floats) you propose. For a square patch, bezier_vnf works with just 4 control points. For a planar patch, where the boundary is a cubic bezier, 8 control points it interprets as two layers of 4 points each. It would be nice if there were something like https://github.com/butcherg/wxpolygon that worked with Apple Vision Pro that let you work with 3D models in with your hands and eyes to reach into the simulated 3D space and grab a control point to move it slightly in 3D space, writing back to a prepared .scad file. In the same way wxpolygon doesn't work with arbitrary .scad files but it does let you work with its text files that are compatible with OpenSCAD.