Difference between modelling with Openscad and Freecad

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Difference between modelling with Openscad and Freecad

Robin2
I don't mean the user-interface, which is obviously very different between
Openscad and Freecad. Different people like different interfaces but anyone
could learn either or both of them if necessary.

It seems to me there is a more fundamental difference. With Freecad (and
other similar CAD programs) you can define an object and later "ask
questions" about that object. For example you can select a point that is the
corner of a cube and it will tell you the coordinates in 3D space. And you
can locate the surface of a face of the cube even though it may have been
rotated or scaled.

However with Openscad the process of defining a model is mono-directional.
You define the object (such as a cube) and you can have no further
interaction with it. You cannot "ask questions".

Is this a fair assessment, or am I completely muddled?

As I see it very many projects can be created with an Openscad approach -
i.e. without ever needing to be able to "ask questions". But I suspect there
are some projects where the ability to easily locate a point or a surface of
an existing object would be essential. And for those cases Openscad would
not be an option.

...R



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Re: Difference between modelling with Openscad and Freecad

nophead
Yes you can't query the geometry in OpenSCAD but I never need to do that because I specify the geometry precisely with maths. 

I don't make anything with hand tools, so I don't need dimensioned drawings. I make my designs so that they fit around parts they need to mount or mate with. I don't care what the final dimensions are, they are often far from round numbers due to the build up of parameters and clearances and radii. If I want to sanity check something, I examine the STL in NetFabb before printing it.

Before OpenSCAD I used CoCreate but since switching to OpenSCAD I would never consider a GUI based CAD system because I a computer programmer, not a mechanical design engineer. I can't even sketch anything in 3D and have difficulty imagining 3D shapes. I start with a mental model of how the non printed parts need to be arranged and design the plastic around them.

On Wed, 2 Oct 2019 at 11:35, Robin2 <[hidden email]> wrote:
I don't mean the user-interface, which is obviously very different between
Openscad and Freecad. Different people like different interfaces but anyone
could learn either or both of them if necessary.

It seems to me there is a more fundamental difference. With Freecad (and
other similar CAD programs) you can define an object and later "ask
questions" about that object. For example you can select a point that is the
corner of a cube and it will tell you the coordinates in 3D space. And you
can locate the surface of a face of the cube even though it may have been
rotated or scaled.

However with Openscad the process of defining a model is mono-directional.
You define the object (such as a cube) and you can have no further
interaction with it. You cannot "ask questions".

Is this a fair assessment, or am I completely muddled?

As I see it very many projects can be created with an Openscad approach -
i.e. without ever needing to be able to "ask questions". But I suspect there
are some projects where the ability to easily locate a point or a surface of
an existing object would be essential. And for those cases Openscad would
not be an option.

...R



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Re: Difference between modelling with Openscad and Freecad

cacb
In reply to this post by Robin2
On 2019-10-02 12:42, Robin2 wrote:

> It seems to me there is a more fundamental difference. With Freecad
> (and
> other similar CAD programs) you can define an object and later "ask
> questions" about that object. For example you can select a point that
> is the
> corner of a cube and it will tell you the coordinates in 3D space. And
> you
> can locate the surface of a face of the cube even though it may have
> been
> rotated or scaled.
>
> However with Openscad the process of defining a model is
> mono-directional.
> You define the object (such as a cube) and you can have no further
> interaction with it. You cannot "ask questions".
>
> Is this a fair assessment, or am I completely muddled?

It is a fair assessment.

OpenSCAD and similar programs are based on the Constructive Solid
Geometry method (
https://en.wikipedia.org/wiki/Constructive_solid_geometry ), which is
kind of an implicit way of defining a model, which makes it harder to
refer to details in the model. Another thing is that the OpenSCAD
language explicitly does not allow any model queries, this is a design
choice. Another difference is that the OpenSCAD internal model
representation is mesh based using CGAL, which is fundamentally
different from the internal model representation in FreeCAD.

In FreeCAD, the internal representation is based on OpenCascade, which
is a boundary representation model (BREP), and not a mesh model. The
OpenCascade model is much more complex and more equivalent to
traditional CAD programs. OpenSCAD (and AngelCAD) are not directly
comparable because of the mesh representation.

Whether you can "ask questions" or not is related to the internal
representation and difficulties of referring to parts of the model, but
it is not the whole story. It is also a question of design philosophy.

Carsten Arnholm

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Re: Difference between modelling with Openscad and Freecad

OpenSCAD mailing list
In reply to this post by Robin2
I am of the opinion that if one creates OpenSCAD code in a parametric manner, it is not necessary to query an object. By creating the object in this way, you've "told" OpenSCAD everything that you'd need to know later.

cube([10, 20, 5]); definition is fine for many.
cube([b_width, b_depth, b_height]); allows for referencing those assignments as often as necessary. If location is important, having parametric values in a translate command provides that information for future use.

I learned this method from another OpenSCAD user, many moons ago, and I'm thankful for having been put on the right track. As I assist others in our makerspace, I do my best to pass along what I've learned.

On Wednesday, October 2, 2019, 6:35:37 AM EDT, Robin2 <[hidden email]> wrote:


I don't mean the user-interface, which is obviously very different between
Openscad and Freecad. Different people like different interfaces but anyone
could learn either or both of them if necessary.

It seems to me there is a more fundamental difference. With Freecad (and
other similar CAD programs) you can define an object and later "ask
questions" about that object. For example you can select a point that is the
corner of a cube and it will tell you the coordinates in 3D space. And you
can locate the surface of a face of the cube even though it may have been
rotated or scaled.

However with Openscad the process of defining a model is mono-directional.
You define the object (such as a cube) and you can have no further
interaction with it. You cannot "ask questions".

Is this a fair assessment, or am I completely muddled?

As I see it very many projects can be created with an Openscad approach -
i.e. without ever needing to be able to "ask questions". But I suspect there
are some projects where the ability to easily locate a point or a surface of
an existing object would be essential. And for those cases Openscad would
not be an option.

...R



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Re: Difference between modelling with Openscad and Freecad

acwest
There are two use cases I can think of for being able to query objects for information. One is when you import external objects and then wish to add things to them. The second is to make implementing generic library code.
In the first instance, I spend a LOT of time rendering objects with shadow cubes in various positions to determine the actual dimensions of the imported objects. This work then has to be repeated whenever the original object is updated to a new version. Tinkercad appears to be particularly bad for putting objects in different positions every time... 
The second instance can be worked around by adding parameters but it is essentially redundant information. For example, a module to put a hole through a cube could have parameters to specify the size and the orientation of the cube, but this is essentially redundant and prone to failure. Any time the same data needs to be specified twice, you are making updates to the code more difficult to get right. 

On Wed, 2 Oct 2019, 09:08 fred via Discuss, <[hidden email]> wrote:
I am of the opinion that if one creates OpenSCAD code in a parametric manner, it is not necessary to query an object. By creating the object in this way, you've "told" OpenSCAD everything that you'd need to know later.

cube([10, 20, 5]); definition is fine for many.
cube([b_width, b_depth, b_height]); allows for referencing those assignments as often as necessary. If location is important, having parametric values in a translate command provides that information for future use.

I learned this method from another OpenSCAD user, many moons ago, and I'm thankful for having been put on the right track. As I assist others in our makerspace, I do my best to pass along what I've learned.

On Wednesday, October 2, 2019, 6:35:37 AM EDT, Robin2 <[hidden email]> wrote:


I don't mean the user-interface, which is obviously very different between
Openscad and Freecad. Different people like different interfaces but anyone
could learn either or both of them if necessary.

It seems to me there is a more fundamental difference. With Freecad (and
other similar CAD programs) you can define an object and later "ask
questions" about that object. For example you can select a point that is the
corner of a cube and it will tell you the coordinates in 3D space. And you
can locate the surface of a face of the cube even though it may have been
rotated or scaled.

However with Openscad the process of defining a model is mono-directional.
You define the object (such as a cube) and you can have no further
interaction with it. You cannot "ask questions".

Is this a fair assessment, or am I completely muddled?

As I see it very many projects can be created with an Openscad approach -
i.e. without ever needing to be able to "ask questions". But I suspect there
are some projects where the ability to easily locate a point or a surface of
an existing object would be essential. And for those cases Openscad would
not be an option.

...R



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Re: Difference between modelling with Openscad and Freecad

nophead
I never specify the same thing twice. If I need a position twice I usually make it a module that positions its children and call it multiple times.

On Wed, 2 Oct 2019 at 14:27, A. Craig West <[hidden email]> wrote:
There are two use cases I can think of for being able to query objects for information. One is when you import external objects and then wish to add things to them. The second is to make implementing generic library code.
In the first instance, I spend a LOT of time rendering objects with shadow cubes in various positions to determine the actual dimensions of the imported objects. This work then has to be repeated whenever the original object is updated to a new version. Tinkercad appears to be particularly bad for putting objects in different positions every time... 
The second instance can be worked around by adding parameters but it is essentially redundant information. For example, a module to put a hole through a cube could have parameters to specify the size and the orientation of the cube, but this is essentially redundant and prone to failure. Any time the same data needs to be specified twice, you are making updates to the code more difficult to get right. 

On Wed, 2 Oct 2019, 09:08 fred via Discuss, <[hidden email]> wrote:
I am of the opinion that if one creates OpenSCAD code in a parametric manner, it is not necessary to query an object. By creating the object in this way, you've "told" OpenSCAD everything that you'd need to know later.

cube([10, 20, 5]); definition is fine for many.
cube([b_width, b_depth, b_height]); allows for referencing those assignments as often as necessary. If location is important, having parametric values in a translate command provides that information for future use.

I learned this method from another OpenSCAD user, many moons ago, and I'm thankful for having been put on the right track. As I assist others in our makerspace, I do my best to pass along what I've learned.

On Wednesday, October 2, 2019, 6:35:37 AM EDT, Robin2 <[hidden email]> wrote:


I don't mean the user-interface, which is obviously very different between
Openscad and Freecad. Different people like different interfaces but anyone
could learn either or both of them if necessary.

It seems to me there is a more fundamental difference. With Freecad (and
other similar CAD programs) you can define an object and later "ask
questions" about that object. For example you can select a point that is the
corner of a cube and it will tell you the coordinates in 3D space. And you
can locate the surface of a face of the cube even though it may have been
rotated or scaled.

However with Openscad the process of defining a model is mono-directional.
You define the object (such as a cube) and you can have no further
interaction with it. You cannot "ask questions".

Is this a fair assessment, or am I completely muddled?

As I see it very many projects can be created with an Openscad approach -
i.e. without ever needing to be able to "ask questions". But I suspect there
are some projects where the ability to easily locate a point or a surface of
an existing object would be essential. And for those cases Openscad would
not be an option.

...R



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Re: Difference between modelling with Openscad and Freecad

Robin2
In reply to this post by cacb
cacb wrote
> It is a fair assessment.

Thanks, and also to @nophead.

I'm trying to figure out how to explain the differences to a novice without
him or her needing to understand the technical foundations so that they can
decide which program is best for what they want to make. A novice will have
to take the trouble to learn no matter what program they decide to use - so
they should not waste time learning one that cannot meet their needs or
waste time learning a complex program if a simpler one would be sufficient.

There are many instructional videos on Youtube (for example making a fidget
spinner) that demonstrate the different programs. But the reality is that
the person making the video already knows how to use the program so the
video does not give a fair impression of how easy it would be for the
novice.

If you know the basics of programming then Openscad's learning curve is a
lot more gentle. But, at least to start with, I suspect it is just as
impenetrable as the other programs for someone who has no experience of
programming and does not know how to conceive a programmed solution for a
problem.

...R




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Re: Difference between modelling with Openscad and Freecad

nophead
>  I suspect it is just as impenetrable as the other programs for someone who has no experience of programming and does not know how to conceive a programmed solution for a problem.

Yes I would think so, but it is a CAD tool for programmers, not the general public. Mechanical engineers I know would use a conventional CAD program and would have no idea how to write programs or use OpenSCAD and even a good friend that is an experienced programmer prefers conventional CAD and thinks I am mad to use OpenSCAD.

On Wed, 2 Oct 2019 at 14:29, Robin2 <[hidden email]> wrote:
cacb wrote
> It is a fair assessment.

Thanks, and also to @nophead.

I'm trying to figure out how to explain the differences to a novice without
him or her needing to understand the technical foundations so that they can
decide which program is best for what they want to make. A novice will have
to take the trouble to learn no matter what program they decide to use - so
they should not waste time learning one that cannot meet their needs or
waste time learning a complex program if a simpler one would be sufficient.

There are many instructional videos on Youtube (for example making a fidget
spinner) that demonstrate the different programs. But the reality is that
the person making the video already knows how to use the program so the
video does not give a fair impression of how easy it would be for the
novice.

If you know the basics of programming then Openscad's learning curve is a
lot more gentle. But, at least to start with, I suspect it is just as
impenetrable as the other programs for someone who has no experience of
programming and does not know how to conceive a programmed solution for a
problem.

...R




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Re: Difference between modelling with Openscad and Freecad

Ronaldo
Besides his or her preference for a programmer's approach in modelling, the OpenSCAD user should be fairly comfortable with geometry and math.

A quarta, 2/10/2019, 14:36, nop head <[hidden email]> escreveu:
>  I suspect it is just as impenetrable as the other programs for someone who has no experience of programming and does not know how to conceive a programmed solution for a problem.

Yes I would think so, but it is a CAD tool for programmers, not the general public. Mechanical engineers I know would use a conventional CAD program and would have no idea how to write programs or use OpenSCAD and even a good friend that is an experienced programmer prefers conventional CAD and thinks I am mad to use OpenSCAD.

On Wed, 2 Oct 2019 at 14:29, Robin2 <[hidden email]> wrote:
cacb wrote
> It is a fair assessment.

Thanks, and also to @nophead.

I'm trying to figure out how to explain the differences to a novice without
him or her needing to understand the technical foundations so that they can
decide which program is best for what they want to make. A novice will have
to take the trouble to learn no matter what program they decide to use - so
they should not waste time learning one that cannot meet their needs or
waste time learning a complex program if a simpler one would be sufficient.

There are many instructional videos on Youtube (for example making a fidget
spinner) that demonstrate the different programs. But the reality is that
the person making the video already knows how to use the program so the
video does not give a fair impression of how easy it would be for the
novice.

If you know the basics of programming then Openscad's learning curve is a
lot more gentle. But, at least to start with, I suspect it is just as
impenetrable as the other programs for someone who has no experience of
programming and does not know how to conceive a programmed solution for a
problem.

...R




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Re: Difference between modelling with Openscad and Freecad

Robin2
In reply to this post by nophead
nophead wrote
> Yes I would think so, but it is a CAD tool for programmers, not the
> general public.

That seems to me a very narrow marketing concept.

I agree that professional engineers are not the target market but shouldn't
the Openscad community be looking for ways to get as many hobbyists as
possible to use Openscad - even if they are not programmers?

...R



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Re: Difference between modelling with Openscad and Freecad

mmaggio
In reply to this post by Robin2
There are ways to keep track of dimensions in openscad using parameters. If you just type cube([10,2,12]); that doesn't produce a record of what those dimensions where. If they are important or used multiple places it can often be a good idea to start the script by stating parameters.

cube_l = 10;
cube_w = 2;
cube_h =12;

cube([10,2,12]);

Now we know the dimension of the object if we need to reference it later like perhaps to put a mitered piece on it. 

Another neat trick is to put a hashtag in front of an object to make it transparent, this way you know what object in the design that line is referencing. So if you aren't sure if a cylinder is a cut out for a hole or part of a different part of an assembly you can pick it out of the design. Be aware this only applies to the f5 preview and has no effect on the final render. You can also have your finished design and use a #cube(); function to find the bounding box by iterating the size of the cube, your precision is limited but it can be useful to ball park the size of the stock you would need to make something in a subtractive manufacturing process.

Last thing i'll say is that it can be useful to take your design and difference it from a cube which you manipulate to form different cutouts. Obviously only relevant if you have internal features, but can be very helpful.

Openscad is powerful when you can express the final shape in terms of a mathmatical relationship between objects, or when some really smart person made a package which does exactly what you want and you can scale it to your application.


On Wed, Oct 2, 2019 at 5:35 AM Robin2 <[hidden email]> wrote:
I don't mean the user-interface, which is obviously very different between
Openscad and Freecad. Different people like different interfaces but anyone
could learn either or both of them if necessary.

It seems to me there is a more fundamental difference. With Freecad (and
other similar CAD programs) you can define an object and later "ask
questions" about that object. For example you can select a point that is the
corner of a cube and it will tell you the coordinates in 3D space. And you
can locate the surface of a face of the cube even though it may have been
rotated or scaled.

However with Openscad the process of defining a model is mono-directional.
You define the object (such as a cube) and you can have no further
interaction with it. You cannot "ask questions".

Is this a fair assessment, or am I completely muddled?

As I see it very many projects can be created with an Openscad approach -
i.e. without ever needing to be able to "ask questions". But I suspect there
are some projects where the ability to easily locate a point or a surface of
an existing object would be essential. And for those cases Openscad would
not be an option.

...R



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Rosalind Franklin University of Medicine and Science
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Office: 224-570-7954
Cell: 815-703-2879 
"Take chances, make mistakes, and get messy!!" - Mrs. Frizzle, PhD

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Re: Difference between modelling with Openscad and Freecad

nophead
> That seems to me a very narrow marketing concept.

Nothing is for sale here.

>I agree that professional engineers are not the target market but shouldn't the Openscad community be looking for ways to get as many hobbyists as possible to use Openscad - even if they are not programmers?

I don't know. I would never recommend it to anyone that isn't a programmer, particularly now that there are good free CAD tools, both open and closed source. Writing software is a very slow process and so is designing objects with OpenSCAD. When I see what James Bruton knocks up with Fusion360 I realise it is much more productive that coding in OpenSCAD.


On Wed, 2 Oct 2019 at 17:50, Matt Maggio <[hidden email]> wrote:
There are ways to keep track of dimensions in openscad using parameters. If you just type cube([10,2,12]); that doesn't produce a record of what those dimensions where. If they are important or used multiple places it can often be a good idea to start the script by stating parameters.

cube_l = 10;
cube_w = 2;
cube_h =12;

cube([10,2,12]);

Now we know the dimension of the object if we need to reference it later like perhaps to put a mitered piece on it. 

Another neat trick is to put a hashtag in front of an object to make it transparent, this way you know what object in the design that line is referencing. So if you aren't sure if a cylinder is a cut out for a hole or part of a different part of an assembly you can pick it out of the design. Be aware this only applies to the f5 preview and has no effect on the final render. You can also have your finished design and use a #cube(); function to find the bounding box by iterating the size of the cube, your precision is limited but it can be useful to ball park the size of the stock you would need to make something in a subtractive manufacturing process.

Last thing i'll say is that it can be useful to take your design and difference it from a cube which you manipulate to form different cutouts. Obviously only relevant if you have internal features, but can be very helpful.

Openscad is powerful when you can express the final shape in terms of a mathmatical relationship between objects, or when some really smart person made a package which does exactly what you want and you can scale it to your application.


On Wed, Oct 2, 2019 at 5:35 AM Robin2 <[hidden email]> wrote:
I don't mean the user-interface, which is obviously very different between
Openscad and Freecad. Different people like different interfaces but anyone
could learn either or both of them if necessary.

It seems to me there is a more fundamental difference. With Freecad (and
other similar CAD programs) you can define an object and later "ask
questions" about that object. For example you can select a point that is the
corner of a cube and it will tell you the coordinates in 3D space. And you
can locate the surface of a face of the cube even though it may have been
rotated or scaled.

However with Openscad the process of defining a model is mono-directional.
You define the object (such as a cube) and you can have no further
interaction with it. You cannot "ask questions".

Is this a fair assessment, or am I completely muddled?

As I see it very many projects can be created with an Openscad approach -
i.e. without ever needing to be able to "ask questions". But I suspect there
are some projects where the ability to easily locate a point or a surface of
an existing object would be essential. And for those cases Openscad would
not be an option.

...R



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Resuscitation Institute (Rm. 1.380)
Department of Medicine
Rosalind Franklin University of Medicine and Science
3333, Green Bay Rd, North Chicago, IL - 60064.
Office: 224-570-7954
Cell: 815-703-2879 
"Take chances, make mistakes, and get messy!!" - Mrs. Frizzle, PhD
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Re: Difference between modelling with Openscad and Freecad

Robin2
nophead wrote
> Nothing is for sale here.

That does not mean that the product should not be marketed - that is, if you
want to widen the user base.


> When I see what James Bruton knocks up with Fusion360 I
> realise it is much more productive that coding in OpenSCAD.

I don't know who James is but I suspect he is very familiar with Fusion360.

I'm thinking of the novice who knows none of the CAD programs and may only
want to build one or two models in a year. For that sort of user a system
that requires very little learning will be very attractive. I think Openscad
can be that system.

...R



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Re: Difference between modelling with Openscad and Freecad

OpenSCAD mailing list
I like math. I like geometry, algebra, trigonometry and even one semester of calculus, but don't ask me to remember any of the latter!

Trying to engage our makerspace members in OpenSCAD hasn't been fruitless, but as soon as numbers come into play, all bets are off. So far, most of them are full GUI users, ala Tinkercad or rarely Onshape, so having to type (no typing skills either) in words and do math and create geometry scares away most.

Recently a new member, with a passing interest in programming became aware of both OpenSCAD and Solvespace. The former you know, the latter is GUI, but parametric and constrained. Useful for a variety of things and a handy tool for the toolbox.

The new member, let's call him John (because it's his name) embraced OpenSCAD with an enthusiasm I've not seen before. He used the same method I enjoy. Look at someone else's work, try something, if it doesn't work, try something else and of course, trouble shoot why the first one didn't cut it.

Every person takes a different approach to a modeling program, and OpenSCAD certainly fits for many people.

The price is hard to beat.

On Wednesday, October 2, 2019, 3:25:11 PM EDT, Robin2 <[hidden email]> wrote:


nophead wrote
> Nothing is for sale here.

That does not mean that the product should not be marketed - that is, if you
want to widen the user base.


> When I see what James Bruton knocks up with Fusion360 I
> realise it is much more productive that coding in OpenSCAD.

I don't know who James is but I suspect he is very familiar with Fusion360.

I'm thinking of the novice who knows none of the CAD programs and may only
want to build one or two models in a year. For that sort of user a system
that requires very little learning will be very attractive. I think Openscad
can be that system.


...R



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Re: Difference between modelling with Openscad and Freecad

Robin2
OpenSCAD mailing list wrote
> The price is hard to beat.

Same as its competitors - Solvespace and Freecad.

So the competition must be fought with something other than price - such as
an easier learning curve?

...R





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Re: Difference between modelling with Openscad and Freecad

Troberg
In reply to this post by OpenSCAD mailing list
OpenSCAD mailing list wrote
> I am of the opinion that if one creates OpenSCAD code in a parametric
> manner, it is not necessary to query an object. By creating the object in
> this way, you've "told" OpenSCAD everything that you'd need to know later.

Well, it's not strictly necessary, true, but in some cases, it would be very
handy.

Examples:

When things move around a lot. Think of a robot arm, with several bend
points. Sure, build it part by part and be careful, and you can do it, but
occasionally (for example if you do an anim), you might want to know where
the claw is without having to to do all the math.

Say that you are doing a an axle, with bunches of nuts and washers, passing
through several  other bits. Sure, the math is easy, but if components are
designed as modules, I need to check out how thick a nut or a washer is,
instead of just "stack them".

Making rounded/chamfered corners on parts. If you could just query the item,
it would be pretty simple to just get the needed dimensions and procedurally
add the roundings/chamfers.



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Re: Difference between modelling with Openscad and Freecad

nophead
For a complex assembly like a robot arm I would have modules to position each segment onto the last one. So there would be say shoulder_upper_arm_position(), upper_arm_forearm_position() and forearm_wrist_position().

In the arm assembly the hand would be a child of the forearm, placed with forearm_wrist_position() and the forearm would be a child of the upper arm, positioned with  upper_arm_forearm_position (), etc.

If I want to say put a ring on a finger it would simply be a matter of calling the right sequence of positioning modules, no extra maths at all. something like:

left_shoulder_position()  shoulder_upper_arm_position () upper_arm_forearm_position() forearm_wrist_position() wrist_ring_finger_position()  ...  ring();

The joint positions might be parameters to each positioning module, or perhaps $variables.

The position of the ring would be a long chain of transformations but that is hidden. If I wanted it in X,Y,Z coordinates I would put the maths from the positioning modules into into functions with the same name. Then the module version would simply be

module  shoulder_upper_arm_position ()  multmatrix(shoulder_upper_arm_position() ) children();

Then I could call the function versions and multiply the matrices together to get a transformation matrix the goes from the origin of the robot to the ring. Mulitpling that by [0, 0, 0, 1] gives the coordinate of the ring.

For stacking washer, my washer and nut modules position their children on top of themselves. So nut(..) washer(..) nut(..) washer(..)  screw(..)  would build a washer kebab.



On Thu, 3 Oct 2019 at 07:34, Troberg <[hidden email]> wrote:
OpenSCAD mailing list wrote
> I am of the opinion that if one creates OpenSCAD code in a parametric
> manner, it is not necessary to query an object. By creating the object in
> this way, you've "told" OpenSCAD everything that you'd need to know later.

Well, it's not strictly necessary, true, but in some cases, it would be very
handy.

Examples:

When things move around a lot. Think of a robot arm, with several bend
points. Sure, build it part by part and be careful, and you can do it, but
occasionally (for example if you do an anim), you might want to know where
the claw is without having to to do all the math.

Say that you are doing a an axle, with bunches of nuts and washers, passing
through several  other bits. Sure, the math is easy, but if components are
designed as modules, I need to check out how thick a nut or a washer is,
instead of just "stack them".

Making rounded/chamfered corners on parts. If you could just query the item,
it would be pretty simple to just get the needed dimensions and procedurally
add the roundings/chamfers.



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Re: Difference between modelling with Openscad and Freecad

Troberg
Neat solutions, nophead, but, as I said, it can be done in other ways, but
sometimes, it would be nice to do be able to ask objects for their
properties. Syntactical sugar has its place as well.



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Re: Difference between modelling with Openscad and Freecad

nophead
I express all the properties I need for my objects with functions and modules. Each parametric object is represented by a list with a set of accessor functions, so nothing is specified twice and I don't need to query the geometry. All the important features of an object are built with its accessor functions. It is a bit clunky as there is a lot of boiler plate to write but it is very simple code in a simple language, so should be easily understood.

Syntactic sugar would be object.property instead of object_property(object). Function literals will allow functions to be embedded in the property list, so objects can be polymorphic.

On Thu, 3 Oct 2019 at 11:56, Troberg <[hidden email]> wrote:
Neat solutions, nophead, but, as I said, it can be done in other ways, but
sometimes, it would be nice to do be able to ask objects for their
properties. Syntactical sugar has its place as well.



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Re: Difference between modelling with Openscad and Freecad

Steven Dick
In reply to this post by Troberg
What OpenSCAD is missing that traditional cad programs have is the
ability to "snap". two pieces together.

Sure you can keep track of where you put the holes, etc., but
something like intersection() creates new surfaces that may be
difficult to find the edges and surface tangents of, may require
complex trigonometry and/or geometry to calculate...

On Thu, Oct 3, 2019 at 6:56 AM Troberg <[hidden email]> wrote:

>
> Neat solutions, nophead, but, as I said, it can be done in other ways, but
> sometimes, it would be nice to do be able to ask objects for their
> properties. Syntactical sugar has its place as well.
>
>
>
> --
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>
> _______________________________________________
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