Sketcher tutorial

A place to share learning material: written tutorials, videos, etc.
100th man
Posts: 2
Joined: Thu Sep 10, 2020 7:07 pm

Re: Sketcher tutorial

Postby 100th man » Thu Sep 10, 2020 8:02 pm

Thank you Christoph Blaue
Improved several usage methods for me as a recent FreeCAD user. Forty-five days ago I downloaded and began. With a bit of old AutoCad familiarity. Well, your tutorial inspired me to write a thank you and even registered to do so.
There are a few things I should probably know "before" this tutorial, like when I need two bodies. Does that generate two parts that can be movement constrained by constrained datum lines? Looking forward to your chapters that help locate sketches, when user defined coordinates are helpful or needed.
The program has already been helpful for drawings I would have difficulty defining adequate for the build-able objects I hope for, much appreciation to all contributors.
Concise is not gonna happen but I think you have well packaged a well rounded sketcher tutorial. I will practice the items I recall, re-read it and maybe even do a couple of the demonstrations.
Peter DeKraker
p[.s.
Probably just a silly thought but...
What if entangle particles are actually one particle in one place at aspects of a wormwhole.
Same thing no? Maybe FreeCAD v29
chrisb
Posts: 29060
Joined: Tue Mar 17, 2015 9:14 am

Re: Sketcher tutorial

Postby chrisb » Thu Sep 10, 2020 8:44 pm

Thanks for the feedback. If it is useful than it was worth the work.
A Sketcher Lecture with in-depth information is available in English, auf deutsch, en français, en español.
User avatar
thomas-neemann
Posts: 1547
Joined: Wed Jan 22, 2020 6:03 pm

Re: Sketcher tutorial

Postby thomas-neemann » Wed Oct 21, 2020 9:45 am

very good video about sketcher:

phpBB [video]
ajoeiam
Posts: 147
Joined: Sun Mar 03, 2019 9:36 pm

Re: Sketcher tutorial

Postby ajoeiam » Wed Oct 28, 2020 8:17 pm

OS: Debian GNU/Linux bullseye/sid (LXQt/lightdm-xsession)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.21857 (Git) AppImage
Build type: Release
Branch: master
Hash: 750c169a6cb999f084915494f2fbec7c07297aae
Python version: 3.8.2
Qt version: 5.12.5
Coin version: 4.0.0
OCC version: 7.4.0

I have worked through the sketcher pdf a number of times.

I'm still struggling to do something that 'should' be simple.

When I draw a rectangle (at this point I'm using 4 lines).
Constraints:
1. one long side
2. end point
3. short side
4. end point
5. end point
6 end point
7. long walls equal
8. short walls equal
9. long wall length defined
10. short wall length defined
11. long wall length defined as an equivalence
12. one short and one long wall defined as being perpendicular
13. 2nd short wall and second long wall defined as being perpendicular
14. short wall length defined as an equivalence

listed as an under-constrained sketch with 2 degrees of freedom

if this were a system of defined sticks this system is not moveable (no way no how).
what further constrains are needed?
kisolre
Posts: 2372
Joined: Wed Nov 21, 2018 1:13 pm

Re: Sketcher tutorial

Postby kisolre » Wed Oct 28, 2020 8:26 pm

ajoeiam wrote:
Wed Oct 28, 2020 8:17 pm
OS: Debian GNU/Linux bullseye/sid (LXQt/lightdm-xsession)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.21857 (Git) AppImage
Build type: Release
Branch: master
Hash: 750c169a6cb999f084915494f2fbec7c07297aae
Python version: 3.8.2
Qt version: 5.12.5
Coin version: 4.0.0
OCC version: 7.4.0

I have worked through the sketcher pdf a number of times.

I'm still struggling to do something that 'should' be simple.

When I draw a rectangle (at this point I'm using 4 lines).
Constraints:
1. one long side
2. end point
3. short side
4. end point
5. end point
6 end point
7. long walls equal
8. short walls equal
9. long wall length defined
10. short wall length defined
11. long wall length defined as an equivalence
12. one short and one long wall defined as being perpendicular
13. 2nd short wall and second long wall defined as being perpendicular
14. short wall length defined as an equivalence

listed as an under-constrained sketch with 2 degrees of freedom

if this were a system of defined sticks this system is not moveable (no way no how).
what further constrains are needed?
Without the actual sketch it is just a guess: I don't see anywhere fixing relative to the origin or X, Y axes.
chrisb
Posts: 29060
Joined: Tue Mar 17, 2015 9:14 am

Re: Sketcher tutorial

Postby chrisb » Wed Oct 28, 2020 9:29 pm

If it's not what kisolre guessed, upload the file.
A Sketcher Lecture with in-depth information is available in English, auf deutsch, en français, en español.
ajoeiam
Posts: 147
Joined: Sun Mar 03, 2019 9:36 pm

Re: Sketcher tutorial

Postby ajoeiam » Thu Oct 29, 2020 11:49 am

kisolre wrote:
Wed Oct 28, 2020 8:26 pm
ajoeiam wrote:
Wed Oct 28, 2020 8:17 pm
OS: Debian GNU/Linux bullseye/sid (LXQt/lightdm-xsession)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.21857 (Git) AppImage
Build type: Release
Branch: master
Hash: 750c169a6cb999f084915494f2fbec7c07297aae
Python version: 3.8.2
Qt version: 5.12.5
Coin version: 4.0.0
OCC version: 7.4.0

I have worked through the sketcher pdf a number of times.

I'm still struggling to do something that 'should' be simple.

When I draw a rectangle (at this point I'm using 4 lines).
Constraints:
1. one long side
2. end point
3. short side
4. end point
5. end point
6 end point
7. long walls equal
8. short walls equal
9. long wall length defined
10. short wall length defined
11. long wall length defined as an equivalence
12. one short and one long wall defined as being perpendicular
13. 2nd short wall and second long wall defined as being perpendicular
14. short wall length defined as an equivalence

listed as an under-constrained sketch with 2 degrees of freedom

if this were a system of defined sticks this system is not moveable (no way no how).
what further constrains are needed?
Without the actual sketch it is just a guess: I don't see anywhere fixing relative to the origin or X, Y axes.
Thank you - - - - - those were the missing constraints.

Question -- - - is there a more streamlined method of constraining a rectangle?
Somehow 16 data values to describe a rectangle seems a bit excessive.
chrisb
Posts: 29060
Joined: Tue Mar 17, 2015 9:14 am

Re: Sketcher tutorial

Postby chrisb » Thu Oct 29, 2020 11:54 am

See my Sketcher Lecture, page 31.
A Sketcher Lecture with in-depth information is available in English, auf deutsch, en français, en español.
ajoeiam
Posts: 147
Joined: Sun Mar 03, 2019 9:36 pm

Re: Sketcher tutorial

Postby ajoeiam » Thu Oct 29, 2020 11:33 pm

chrisb wrote:
Thu Oct 29, 2020 11:54 am
See my Sketcher Lecture, page 31.
Thanks - - - that helped.

Note: (for anyone reading this)
There is only ONE way to actually achieve a fully constrained sketch.
1. sketch rectangle
That gives you your first 8 constraints.
2. place a dot somewhere about in the symmetric center of the rectangle
3. you MUST constrain 2 diagonal points and the center point
(If you do not do this at this point you will not be able to successfully constrain the rectangle!!!)
4. constrain your rectangle vertical distance
5. constrain your rectangle horizontal distance
(it seems that #4 and 5 do not require a specific order)
HTH
chrisb
Posts: 29060
Joined: Tue Mar 17, 2015 9:14 am

Re: Sketcher tutorial

Postby chrisb » Thu Oct 29, 2020 11:59 pm

A rectangle doesn't give 8 degrees of freedom (DOF), only 4, because it is fully defined by two diagonal corners, each of them having 2 DOF.
Point 3 in your list can be replaced by constraining a corner point; in the simplest case by creating a coincidence with the origin.
A Sketcher Lecture with in-depth information is available in English, auf deutsch, en français, en español.