Is Clipper as opaque as CGAL?
I know that there’s effectively no access to CGAL during interpretation, and that the dream of being able to poll for dimensions after transformation is going to remain a dream, but is the same true for Clipper?
I have been developing an increasing list of modules and functions that manipulate arrays of points and finding that very helpful for many modelling projects.
It would be fantastic if there was access to clipper’s 2D boolean functions like Union, Difference, Intersection etc… so my question is with regard to the availability of clipper functions in an OpenSCAD program. It it like CGAL and it’s just a closed box, or is it possible that OpenSCAD functions could be made available that performed 2D boolean operations on point lists?
I’m sure this has been asked before, but I did do some research and didn’t come up with any history on this matter, so I do apologize if this has been answered a thousand times before. I appreciate that the power of such functionality is so appealing that if it could be done it would have been done already, but I thought I’d ask.
About 3 months ago I submitted PR#3288 to OpenSCAD to provide full access to ClipperLib Boolean geometry. I’m still waiting to see if it will be accepted and merged.
https://github.com/openscad/openscad/pull/3288
In the meantime, if you really need it, I’ve implemented 2D Boolean geometry in the BOSL2 library. It not yet a complete library yet, but if you really need it, the code is there.
https://github.com/revarbat/BOSL2
-Revar
On Jul 28, 2020, at 4:24 PM, Hugo Jackson hugo@apres.net wrote:
I know that there’s effectively no access to CGAL during interpretation, and that the dream of being able to poll for dimensions after transformation is going to remain a dream, but is the same true for Clipper?
I have been developing an increasing list of modules and functions that manipulate arrays of points and finding that very helpful for many modelling projects.
It would be fantastic if there was access to clipper’s 2D boolean functions like Union, Difference, Intersection etc… so my question is with regard to the availability of clipper functions in an OpenSCAD program. It it like CGAL and it’s just a closed box, or is it possible that OpenSCAD functions could be made available that performed 2D boolean operations on point lists?
I’m sure this has been asked before, but I did do some research and didn’t come up with any history on this matter, so I do apologize if this has been answered a thousand times before. I appreciate that the power of such functionality is so appealing that if it could be done it would have been done already, but I thought I’d ask.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
CGAL isn't a closed box, it is just very very slow. The main reason you
don't get access to geometry is it isn't evaluated with CGAL during a
preview when OpenCSG is used to make pictures of it.
On Wed, 29 Jul 2020 at 01:03, Revar Desmera revarbat@gmail.com wrote:
About 3 months ago I submitted PR#3288 to OpenSCAD to provide full access
to ClipperLib Boolean geometry. I’m still waiting to see if it will be
accepted and merged.
https://github.com/openscad/openscad/pull/3288
In the meantime, if you really need it, I’ve implemented 2D Boolean
geometry in the BOSL2 library. It not yet a complete library yet, but if
you really need it, the code is there.
https://github.com/revarbat/BOSL2
-Revar
On Jul 28, 2020, at 4:24 PM, Hugo Jackson hugo@apres.net wrote:
I know that there’s effectively no access to CGAL during interpretation,
and that the dream of being able to poll for dimensions after
transformation is going to remain a dream, but is the same true for Clipper?
I have been developing an increasing list of modules and functions that
manipulate arrays of points and finding that very helpful for many
modelling projects.
It would be fantastic if there was access to clipper’s 2D boolean
functions like Union, Difference, Intersection etc… so my question is with
regard to the availability of clipper functions in an OpenSCAD program. It
it like CGAL and it’s just a closed box, or is it possible that OpenSCAD
functions could be made available that performed 2D boolean operations on
point lists?
I’m sure this has been asked before, but I did do some research and didn’t
come up with any history on this matter, so I do apologize if this has been
answered a thousand times before. I appreciate that the power of such
functionality is so appealing that if it could be done it would have been
done already, but I thought I’d ask.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Hey, thanks for this… I hope it gets incorporated into the official relase!
On Jul 28, 2020, at 5:02 PM, Revar Desmera revarbat@gmail.com wrote:
About 3 months ago I submitted PR#3288 to OpenSCAD to provide full access to ClipperLib Boolean geometry. I’m still waiting to see if it will be accepted and merged.
https://github.com/openscad/openscad/pull/3288 https://github.com/openscad/openscad/pull/3288
In the meantime, if you really need it, I’ve implemented 2D Boolean geometry in the BOSL2 library. It not yet a complete library yet, but if you really need it, the code is there.
https://github.com/revarbat/BOSL2 https://github.com/revarbat/BOSL2
-Revar
On Jul 28, 2020, at 4:24 PM, Hugo Jackson hugo@apres.net wrote:
I know that there’s effectively no access to CGAL during interpretation, and that the dream of being able to poll for dimensions after transformation is going to remain a dream, but is the same true for Clipper?
I have been developing an increasing list of modules and functions that manipulate arrays of points and finding that very helpful for many modelling projects.
It would be fantastic if there was access to clipper’s 2D boolean functions like Union, Difference, Intersection etc… so my question is with regard to the availability of clipper functions in an OpenSCAD program. It it like CGAL and it’s just a closed box, or is it possible that OpenSCAD functions could be made available that performed 2D boolean operations on point lists?
I’m sure this has been asked before, but I did do some research and didn’t come up with any history on this matter, so I do apologize if this has been answered a thousand times before. I appreciate that the power of such functionality is so appealing that if it could be done it would have been done already, but I thought I’d ask.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
I confess I don’t really know enough to even be asking intelligent questions… but I would submit that speed is not a primary concern if one has access to a functionality that can do something that would be extremely difficult to do otherwise. By way of comparison, I would suggest minkowski… which depending on its application adds signficant processing times for a render… on the other hand, I presume that for some users, that functionality is worth the wait… regardless of how long it takes.
Anyway, I appreciate that I”m probably mixing ‘problems’… in that boolean operations are a different animal than my dream of being able to get the boundaries of an object after an operation is performed rather than having to calculate what it will be independent of the actual operation.
Regardless… OpenSCAD is great!
On Jul 29, 2020, at 12:37 AM, nop head nop.head@gmail.com wrote:
CGAL isn't a closed box, it is just very very slow. The main reason you don't get access to geometry is it isn't evaluated with CGAL during a preview when OpenCSG is used to make pictures of it.
On Wed, 29 Jul 2020 at 01:03, Revar Desmera <revarbat@gmail.com mailto:revarbat@gmail.com> wrote:
About 3 months ago I submitted PR#3288 to OpenSCAD to provide full access to ClipperLib Boolean geometry. I’m still waiting to see if it will be accepted and merged.
https://github.com/openscad/openscad/pull/3288 https://github.com/openscad/openscad/pull/3288
In the meantime, if you really need it, I’ve implemented 2D Boolean geometry in the BOSL2 library. It not yet a complete library yet, but if you really need it, the code is there.
https://github.com/revarbat/BOSL2 https://github.com/revarbat/BOSL2
-Revar
On Jul 28, 2020, at 4:24 PM, Hugo Jackson <hugo@apres.net mailto:hugo@apres.net> wrote:
I know that there’s effectively no access to CGAL during interpretation, and that the dream of being able to poll for dimensions after transformation is going to remain a dream, but is the same true for Clipper?
I have been developing an increasing list of modules and functions that manipulate arrays of points and finding that very helpful for many modelling projects.
It would be fantastic if there was access to clipper’s 2D boolean functions like Union, Difference, Intersection etc… so my question is with regard to the availability of clipper functions in an OpenSCAD program. It it like CGAL and it’s just a closed box, or is it possible that OpenSCAD functions could be made available that performed 2D boolean operations on point lists?
I’m sure this has been asked before, but I did do some research and didn’t come up with any history on this matter, so I do apologize if this has been answered a thousand times before. I appreciate that the power of such functionality is so appealing that if it could be done it would have been done already, but I thought I’d ask.
OpenSCAD mailing list
Discuss@lists.openscad.org mailto:Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
OpenSCAD mailing list
Discuss@lists.openscad.org mailto:Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Minkowski is a powerful tool for modeling. It is less used because it is
not as easy to learn and it is very slow even on preview. The preview of a
model involving minkowski could be dramatically speeded up if the way it is
done avoided CGAL in its last step. As it was reported here, by Torsten, I
think, minkowski operates by first decomposing the objects to be "added" in
convex chunks. The appropriate pairs of chunks are then easily combined
with minkowski (by a fast convex hull) and the union of all these
combinations produces the final result. CGAL is responsible for the
decomposition and the final union. This last step, the more demanding task,
would be a lot faster if it was done like any other union in preview: using
the z-buffer to avoid CGAL. A fast preview of minkowski would increase the
productivity in the developing phase of a project, promoting a broader use
of it, and pushing its reputation of being very slow just to the final
model render.
I confess I don’t really know enough to even be asking intelligent
questions… but I would submit that speed is not a primary concern if one
has access to a functionality that can do something that would be extremely
difficult to do otherwise. By way of comparison, I would suggest minkowski…
which depending on its application adds signficant processing times for a
render… on the other hand, I presume that for some users, that
functionality is worth the wait… regardless of how long it takes.
Anyway, I appreciate that I”m probably mixing ‘problems’… in that boolean
operations are a different animal than my dream of being able to get the
boundaries of an object after an operation is performed rather than having
to calculate what it will be independent of the actual operation.
Regardless… OpenSCAD is great!
Yes I think that would be a good usability improvement as long as convex
decomposition isn't too slow. I haven't come across anything the CGAL does
in a reasonable time.
On Wed, 29 Jul 2020 at 15:27, Ronaldo Persiano rcmpersiano@gmail.com
wrote:
Minkowski is a powerful tool for modeling. It is less used because it is
not as easy to learn and it is very slow even on preview. The preview of a
model involving minkowski could be dramatically speeded up if the way it is
done avoided CGAL in its last step. As it was reported here, by Torsten, I
think, minkowski operates by first decomposing the objects to be "added" in
convex chunks. The appropriate pairs of chunks are then easily combined
with minkowski (by a fast convex hull) and the union of all these
combinations produces the final result. CGAL is responsible for the
decomposition and the final union. This last step, the more demanding task,
would be a lot faster if it was done like any other union in preview: using
the z-buffer to avoid CGAL. A fast preview of minkowski would increase the
productivity in the developing phase of a project, promoting a broader use
of it, and pushing its reputation of being very slow just to the final
model render.
I confess I don’t really know enough to even be asking intelligent
questions… but I would submit that speed is not a primary concern if one
has access to a functionality that can do something that would be extremely
difficult to do otherwise. By way of comparison, I would suggest minkowski…
which depending on its application adds signficant processing times for a
render… on the other hand, I presume that for some users, that
functionality is worth the wait… regardless of how long it takes.
Anyway, I appreciate that I”m probably mixing ‘problems’… in that boolean
operations are a different animal than my dream of being able to get the
boundaries of an object after an operation is performed rather than having
to calculate what it will be independent of the actual operation.
Regardless… OpenSCAD is great!
On 29.07.2020 16:26, Ronaldo Persiano wrote:
Minkowski is a powerful tool for modeling. It is less used because it is
not as easy to learn and it is very slow even on preview. The preview of
a model involving minkowski could be dramatically speeded up if the way
it is done avoided CGAL in its last step. As it was reported here, by
Torsten, I think, minkowski operates by first decomposing the objects to
be "added" in convex chunks. The appropriate pairs of chunks are then
easily combined with minkowski (by a fast convex hull) and the union of
all these combinations produces the final result. CGAL is responsible
for the decomposition and the final union. This last step, the more
demanding task, would be a lot faster if it was done like any other
union in preview: using the z-buffer to avoid CGAL. A fast preview of
minkowski would increase the productivity in the developing phase of a
project, promoting a broader use of it, and pushing its reputation of
being very slow just to the final model render.
The most complicated aspect of Minkowski is subdividing the original
model into a collection of convex parts. I don't think you can avoid
that by some preview smartness. The rest is not too difficult but it is
processor heavy. I have made an independent Carve-based implementation
of Minkowski, so I have a bit of experience.
Carsten Arnholm
On 29.07.20 18:09, Carsten Arnholm wrote:
The most complicated aspect of Minkowski is subdividing the
original model into a collection of convex parts. I don't
think you can avoid that by some preview smartness.
Measurement with CGAL says there might be a chance:
http://forum.openscad.org/rendering-problem-tp29209p29225.html
Summary:
Minkowski: decomposed into 124 convex parts
Minkowski: decomposition took 1.029088 s
...
Minkowski: Computing union of 124 parts
Minkowski: Union done: 26.550561 s
Which again comes back to CGAL being especially slow
with unions.
ciao,
Torsten.
On 7/29/2020 12:37 AM, nop head wrote:
CGAL isn't a closed box, it is just very very slow. The main reason
you don't get access to geometry is it isn't evaluated with CGAL
during a preview when OpenCSG is used to make pictures of it.
I started to write that, but then I saw that the OP asked about offering
boolean operations on point lists, which is a different problem. Or at
least it's at a different point in the pipeline.