C
caterpillar
Sat, May 25, 2019 9:39 AM
The purpose of bend_extrude is to replace bend
https://openhome.cc/eGossip/OpenSCAD/lib-bend.html when you have a 2D
shape. bend_extrude is faster and doesn't produce jagged edges.
Sent from: http://forum.openscad.org/
The purpose of bend_extrude is to replace bend
<https://openhome.cc/eGossip/OpenSCAD/lib-bend.html> when you have a 2D
shape. bend_extrude is faster and doesn't produce jagged edges.
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A
adrianv
Sat, May 25, 2019 12:43 PM
On 2019-05-24 23:41, adrianv wrote:
I suppose it's a somewhat advanced effort, but I don't think it would
be
particularly hard to write a "bent_sweep" module that would take a
polygon
expressed as a series of point coordinates and a second "destination"
polygon also as a series of points. You could project the first
polygon
onto the second one and then build it up to the desired thickness (in
the
normal direction), constructing the vertices and faces of the necessary
polyhedron.
A polygon in OpenSCAD is a 2d object with only (x,y) coordinates, so the
"destination" cannot exist anywhere but in the (x,y) plane. I think you
would "be on your own" having to write such from scratch using lists of
3d coordinates. Possible perhaps, but somewhat inconvenient.
I was suggesting a strategy for producing the desired gear model, not a
fully general approach to melting. In my conception, the gear is defined by
a 2d polygon. The gear in the image is deformed by being wrapped around an
extrusion, so the 3d surface it is wrapped around also has a 2d description.
So you can construct the top and bottom of the "melted" gear through a
projection operation that is relatively simple.
The melting/morphing case is quite different, it begins with an existing
valid 3d model created using any method. Usually keeping the topology of
the model fixed, the shape of the 3d model is modified. If the model
is represented as a polyhedron mesh, either explicitly modeled as such
or the result of mesh based boolean operations, changing the shape
translates to transforming the polyhedron vertex coordinates, using
different transformations for different vertices (i.e. "non-affine
transformation" of the model).
It seems that starting with polyhedron described by a 3d vertex set (and
face list) one could also achieve the desired result. It basically boils
down to the question of representing the desired transformation. The
problem, of course, is that OpenSCAD doesn't expose that information, so you
can't just do it to geometry. You could use one of the existing sweep
modules to generate the necessary input from the 2d gear cross-section.
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cacb wrote
> On 2019-05-24 23:41, adrianv wrote:
>> I suppose it's a somewhat advanced effort, but I don't think it would
>> be
>> particularly hard to write a "bent_sweep" module that would take a
>> polygon
>> expressed as a series of point coordinates and a second "destination"
>> polygon also as a series of points. You could project the first
>> polygon
>> onto the second one and then build it up to the desired thickness (in
>> the
>> normal direction), constructing the vertices and faces of the necessary
>> polyhedron.
>
> A polygon in OpenSCAD is a 2d object with only (x,y) coordinates, so the
> "destination" cannot exist anywhere but in the (x,y) plane. I think you
> would "be on your own" having to write such from scratch using lists of
> 3d coordinates. Possible perhaps, but somewhat inconvenient.
I was suggesting a strategy for producing the desired gear model, not a
fully general approach to melting. In my conception, the gear is defined by
a 2d polygon. The gear in the image is deformed by being wrapped around an
extrusion, so the 3d surface it is wrapped around also has a 2d description.
So you can construct the top and bottom of the "melted" gear through a
projection operation that is relatively simple.
> The melting/morphing case is quite different, it begins with an existing
> valid 3d model created using any method. Usually keeping the topology of
> the model fixed, the *shape* of the 3d model is modified. If the model
> is represented as a polyhedron mesh, either explicitly modeled as such
> or the result of mesh based boolean operations, changing the shape
> translates to transforming the polyhedron vertex coordinates, using
> different transformations for different vertices (i.e. "non-affine
> transformation" of the model).
It seems that starting with polyhedron described by a 3d vertex set (and
face list) one could also achieve the desired result. It basically boils
down to the question of representing the desired transformation. The
problem, of course, is that OpenSCAD doesn't expose that information, so you
can't just do it to geometry. You could use one of the existing sweep
modules to generate the necessary input from the 2d gear cross-section.
--
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C
caterpillar
Sun, May 26, 2019 1:09 AM
I made a melted clock with an animation demo.
https://www.thingiverse.com/thing:3653698
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M
MichaelAtOz
Sun, May 26, 2019 2:42 AM
I made a melted clock with an animation demo.
I get:
This video does not exist.
Sorry about that.
Admin - email* me if you need anything, or if I've done something stupid...
- click on my MichaelAtOz label, there is a link to email me.
Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above.
The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
Sent from: http://forum.openscad.org/
caterpillar wrote
> I made a melted clock with an animation demo.
I get:
This video does not exist.
Sorry about that.
-----
Admin - email* me if you need anything, or if I've done something stupid...
* click on my MichaelAtOz label, there is a link to email me.
Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above.
The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
--
Sent from: http://forum.openscad.org/
M
MichaelAtOz
Sun, May 26, 2019 3:27 AM
This video does not exist.
Sorry about that.
Looks like it don't like Pale Moon, it worked in Firefox...
Pretty nifty.
Admin - email* me if you need anything, or if I've done something stupid...
- click on my MichaelAtOz label, there is a link to email me.
Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above.
The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
Sent from: http://forum.openscad.org/
MichaelAtOz wrote
> This video does not exist.
> Sorry about that.
Looks like it don't like Pale Moon, it worked in Firefox...
Pretty nifty.
-----
Admin - email* me if you need anything, or if I've done something stupid...
* click on my MichaelAtOz label, there is a link to email me.
Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above.
The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
--
Sent from: http://forum.openscad.org/
C
caterpillar
Sun, May 26, 2019 3:27 AM
The video is here.
https://www.youtube.com/watch?v=U5cAOi-gwtY
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P
Parkinbot
Sun, May 26, 2019 1:10 PM
I would have expected the clock to melt over time ... ;-)
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I would have expected the clock to melt over time ... ;-)
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HL
Hans L
Sun, May 26, 2019 2:34 PM
I think the big question is why go through the trouble of modeling plastic
deformation of a printed plastic part when you can get the same slumping
effect with a little post-print heat application(particularly if PLA is
used). Soften in boiling water, or apply a heat gun, or just print in
black+leave in sun (I learned this last one the hard way a few years ago
when I left a Prusa i2 printer in the hatchback of a car for one Texas
summer day, with black PLA used for the frame vertices)
On Sun, May 26, 2019, 8:11 AM Parkinbot rudolf@digitaldocument.de wrote:
I think the big question is why go through the trouble of modeling plastic
deformation of a printed plastic part when you can get the same slumping
effect with a little post-print heat application(particularly if PLA is
used). Soften in boiling water, or apply a heat gun, or just print in
black+leave in sun (I learned this last one the hard way a few years ago
when I left a Prusa i2 printer in the hatchback of a car for one Texas
summer day, with black PLA used for the frame vertices)
On Sun, May 26, 2019, 8:11 AM Parkinbot <rudolf@digitaldocument.de> wrote:
> I would have expected the clock to melt over time ... ;-)
>
>
>
> --
> Sent from: http://forum.openscad.org/
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CA
Carsten Arnholm
Sun, May 26, 2019 3:44 PM
On 26.05.2019 16:34, Hans L wrote:
I think the big question is why go through the trouble of modeling
plastic deformation of a printed plastic part when you can get the same
slumping effect with a little post-print heat application(particularly
if PLA is used).
The small answer is that such techniques are not just for "melting", but
more generally for morphing which has other applications, including
adapting 3d text to a non-flat surface.
Carsten Arnholm
On 26.05.2019 16:34, Hans L wrote:
> I think the big question is why go through the trouble of modeling
> plastic deformation of a printed plastic part when you can get the same
> slumping effect with a little post-print heat application(particularly
> if PLA is used).
The small answer is that such techniques are not just for "melting", but
more generally for morphing which has other applications, including
adapting 3d text to a non-flat surface.
Carsten Arnholm
DM
Doug Moen
Mon, May 27, 2019 12:51 AM
The operation that is being discussed here is often called "bend", and it bends a shape around a cylinder. It's a useful general purpose CAD operation, and it's strange that more CAD programs don't include it. A simple example is adding a bend to a pipe. I often use it for bending long skinny objects into rings.
Another "plastic deformation" that I get a lot of use out of is "twist".
Here's an old SIGGRAPH paper that makes the case for including "bend" and "twist" in CAD programs:
https://www.cs.drexel.edu/~david/Classes/CS586/Papers/p21-barr.pdf
On Sun, May 26, 2019, at 10:35 AM, Hans L wrote:
I think the big question is why go through the trouble of modeling plastic deformation of a printed plastic part when you can get the same slumping effect with a little post-print heat application(particularly if PLA is used). Soften in boiling water, or apply a heat gun, or just print in black+leave in sun (I learned this last one the hard way a few years ago when I left a Prusa i2 printer in the hatchback of a car for one Texas summer day, with black PLA used for the frame vertices)
On Sun, May 26, 2019, 8:11 AM Parkinbot rudolf@digitaldocument.de wrote:
The operation that is being discussed here is often called "bend", and it bends a shape around a cylinder. It's a useful general purpose CAD operation, and it's strange that more CAD programs don't include it. A simple example is adding a bend to a pipe. I often use it for bending long skinny objects into rings.
Another "plastic deformation" that I get a lot of use out of is "twist".
Here's an old SIGGRAPH paper that makes the case for including "bend" and "twist" in CAD programs:
https://www.cs.drexel.edu/~david/Classes/CS586/Papers/p21-barr.pdf
On Sun, May 26, 2019, at 10:35 AM, Hans L wrote:
> I think the big question is why go through the trouble of modeling plastic deformation of a printed plastic part when you can get the same slumping effect with a little post-print heat application(particularly if PLA is used). Soften in boiling water, or apply a heat gun, or just print in black+leave in sun (I learned this last one the hard way a few years ago when I left a Prusa i2 printer in the hatchback of a car for one Texas summer day, with black PLA used for the frame vertices)
>
>
>
>
> On Sun, May 26, 2019, 8:11 AM Parkinbot <rudolf@digitaldocument.de> wrote:
>> I would have expected the clock to melt over time ... ;-)
>>
>>
>>
>> --
>> Sent from: http://forum.openscad.org/
>>
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>> Discuss@lists.openscad.org
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