Notes about Coordinate systems

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manos
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Re: Notes about Coordinate systems

Post by manos »

Shalmeneser wrote: Sat Jul 02, 2022 1:51 pm https://en.wikipedia.org/wiki/Open_file_format : .odt (LibreOffice)
So .odt is file format used by both Windows and Linux users ?
chrisb
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Re: Notes about Coordinate systems

Post by chrisb »

Additions by chrisb in this color. I have also used the strike through for edits, where you need a sharp eye to spot them.
manos wrote: Sat Jul 02, 2022 10:19 am In FreeCAD allThe objects at space are positioned using Coordinate systems. The most used system is the Cartesian.
It is a system with invariable axis and the less used by simple users.
What does this mean? It is the coordinate system used most often by all Part workbench users, and by all Arch and Draft users too.
The following objects DO NOT have their own axis system: Document, Group,
It can well be argued that the coordinate system of the Document is the global one.
For some objects We can view the (Local) Coordinate system of the objects contained in the Body: e.g. Tree view ->Body->Origin and hitting Space.
It doesn't show the CS of the objects inside of the body.
Sketches have their own Coordinate system too which is …….. of the Body in which they are contained.
I don't understand this
Shapes contained in a Body have their own Coordinate system which is … of the Body in which they are contained.
What Shapes are you talking about?
For the objects inside the Body we can create an Auxiliary Local Coordinate system using the command: PartDesign CoordinateSystem.
It's not for the objects inside of a body. It's just a CS, and the main purpose is to attach things to it.
If we want to combine more bodies to make an Assembly we can use a Std Part. A Std Part provides its own (Local) Coordinate System.
Bodies inside a Std Part keep their own coordinate System.
For such a document it seems absolutely necessary to talk about attachments.
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manos
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Re: Notes about Coordinate systems

Post by manos »

GeneFC wrote: Sat Jul 02, 2022 3:02 pm
I do not believe there is any advanced format that is standard and commonly used across all platforms. Limited capability formats such as TXT and PDF are used, of course, but these have either limited capability or limited editability.

Gene
Isn't true that both users of Windows and users of Linux (LibreOffice Writer) can work and know how to work with .doc files ?
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mfro
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Re: Notes about Coordinate systems

Post by mfro »

If that text helps your understanding, good.

I'm not sure, however, if it would help all the other users understanding what coordinate systems are there.

First, FreeCAD does not really have several different coordinate systems, there is basically only one: the global coordinate system. Objects can have a local coordinate system, but FreeCAD will recalculate coordinates from that LCS into global coordinates as you deal with them - LCS are meant to make things easier (not harder) for you, the user.

Think of an analogy where it perfectly makes sense to express the street locations of your hometown in (literally) global coordinates when you're using the maps application on your phone or your GPS device to find your way home. You might as well name the corners of your property of your new house's plans in this same coordinate system, but GPS coordinates will likely give your bricklayer a hard time if he needs to figure out how long your walls are supposed to be or how much open space your windows will need.

In FreeCAD, this is exactly the same: the "Position"-attribute tells everybody where your property (= Body) is located in global coordinates (just like your phone does navigating you home).

The direction of your properties' edges (= orientation of the base planes of your Body's "Origin"-object) is expressed by it's axis vector and rotation angle because its rather unlikely that your property is perfectly aligned to the "global earth planes".

When you design the first wall (= Sketch) of your new house, you might decide you don't want it to be aligned to your property's edge, but rather to the nice view down the valley. This is why sketches can be attached to the body in arbitrary orientation (=Attachment). Now you can draw your sketch with exactly the information (length, window space, ...) your bricklayer will need.

Even better, should your neighbour decide your new house is a nice one and wants to build the same, he can just take your finished plans and give it to his bricklayer, all he needs to adapt is the Position attribute of his own property (=Body). In FreeCAD, you can do exactly the same (e.g. when you clone a Body).
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Shalmeneser
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Re: Notes about Coordinate systems

Post by Shalmeneser »

manos wrote: Sat Jul 02, 2022 3:36 pm Isn't true that both users of Windows and users of Linux (LibreOffice Writer) can work and know how to work with .doc files ?
.doc is evil, period :evil:
GeneFC
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Re: Notes about Coordinate systems

Post by GeneFC »

manos wrote: Sat Jul 02, 2022 3:36 pm
GeneFC wrote: Sat Jul 02, 2022 3:02 pm
Isn't true that both users of Windows and users of Linux (LibreOffice Writer) can work and know how to work with .doc files ?
I can work with anything. I cannot generalize for other Windows and Linux users. (Yes, I do actively use Linux, just not for FreeCAD. :mrgreen: )

Gene
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adrianinsaval
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Re: Notes about Coordinate systems

Post by adrianinsaval »

mfro wrote: Sat Jul 02, 2022 3:54 pm In FreeCAD, this is exactly the same: the "Position"-attribute tells everybody where your property (= Body) is located in global coordinates (just like your phone does navigating you home).
Not at all, an object's placement property is always relative to it's parent coordinate system, all of this is very complex and as chrisb says it's really necessary to talk about placement and attachment to truly understand these subjects.

As for the document format, I just find it annoying having to download a file and open a full blown office text processor just to read/edit some plain text. That's why I pasted the text directly in the forum.
manos
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Re: Notes about Coordinate systems

Post by manos »

mfro wrote: Sat Jul 02, 2022 3:54 pm If that text helps your understanding, good.

I'm not sure, however, if it would help all the other users understanding what coordinate systems are there.

First, FreeCAD does not really have several different coordinate systems, there is basically only one: the global coordinate system. Objects can have a local coordinate system, but FreeCAD will recalculate coordinates from that LCS into global coordinates as you deal with them - LCS are meant to make things easier (not harder) for you, the user.
So I have to correct my phrase: FreeCad offers to its users the possibility of using several coordinate systems.

Do you agree ?
Thanks for your vivid representation of Coordinate system.
manos
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Re: Notes about Coordinate systems

Post by manos »

chrisb wrote: Sat Jul 02, 2022 3:25 pm
manos wrote: Sat Jul 02, 2022 10:19 am In FreeCAD allThe objects at space are positioned using Coordinate systems. The most used system is the Cartesian.
Agree
It is a system with invariable axis and the less used by simple users.
What does this mean? It is the coordinate system used most often by all Part workbench users, and by all Arch and Draft users too.
Part WB and Draft WB are considered obsolete any more. Does PartDesign and Sketcher WB use GCS to that extend ?
.....
For some objects We can view the (Local) Coordinate system of the objects contained in the Body: e.g. Tree view ->Body->Origin and hitting Space.
Agree . The phrase should be "We can view the (Local) Coordinate system of the Body: Tree view ->Body->Origin and hitting Space."
Sketches have their own Coordinate system too which is …….. of the Body in which they are contained.
I don't understand this
Agree . The phrase should be "Sketches have their own Coordinate system too" . We can see it when editing the Sketch.
Shapes contained in a Body have their own Coordinate system which is … of the Body in which they are contained.
What Shapes are you talking about?
The phrase should be "Objects with shape have their own Coordinate System"
For the objects inside the Body we can create an Auxiliary Local Coordinate system using the command: PartDesign CoordinateSystem.
It's not for the objects inside of a body. It's just a CS, and the main purpose is to attach things to it.
The phrase should be:"We can create an Auxiliary Local Coordinate system inside a Body using the command: PartDesign CoordinateSystem.It can be used by objects inside the Body and not only"
If we want to combine more bodies to make an Assembly we can use a Std Part. A Std Part provides its own (Local) Coordinate System.
Bodies inside a Std Part keep their own coordinate System.
For such a document it seems absolutely necessary to talk about attachments.
Of course we will talk about attachments. It will be your punishment of not having written chapter 41 of Sketcher Lecture.
@Chrisb thank you so much.
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Re: Notes about Coordinate systems

Post by drmacro »

Part workbench and Draft workbench are certainly not obsolete.

There are many things that only they do and they are complementary to many other workbenches.

Draft is heavily used in conjunction with the Arch.

IMO, anyone who intends to become really proficient with FreeCAD must be able to use far more than just Part Design workbench.

You should read this link thoroughly and work through the example at the end that creates the same component with each exclusively. https://wiki.freecadweb.org/Part_and_PartDesign
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
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