[Solved] PartDesign: Mirror along X and Y / Point Reflection / Multitranform but only keep result

Post here for help on using FreeCAD's graphical user interface (GUI).
Forum rules
and Helpful information
IMPORTANT: Please click here and read this first, before asking for help

Also, be nice to others! Read the FreeCAD code of conduct!
Post Reply
thomas-huber
Posts: 13
Joined: Wed Jan 26, 2022 4:02 pm
Location: Oberneukirchen, Bavaria

[Solved] PartDesign: Mirror along X and Y / Point Reflection / Multitranform but only keep result

Post by thomas-huber »

Hello FreeCAD community,

I'm in the PartDesign module and want to mirror a pocket along the x AND the y axis at the same time (point reflection through the center)
PartMirror doesn't have that option so I tried Multitranform. But Multitranform keeps the in-between steps. So at the end I have three pockets: The original, the one mirrored around X and the one mirrored around XY.

What can I do?

Thanks
Thomas

OS: KDE Flatpak runtime (X-Cinnamon/cinnamon)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.14555 (Git shallow)
Build type: Release
Branch: (HEAD detached at 0.19.4)
Hash: 476ecf091941bead59b14e44afa6064d5a66afa3
Python version: 3.9.9
Qt version: 5.15.3
Coin version: 4.0.0
OCC version: 7.3.0
Locale: German/Germany (de_DE)
Last edited by thomas-huber on Wed May 18, 2022 12:10 pm, edited 2 times in total.
drmacro
Veteran
Posts: 8872
Joined: Sun Mar 02, 2014 4:35 pm

Re: PartDesign: Mirror along X and Y / Point Reflection / Multitranform but only keep result

Post by drmacro »

thomas-huber wrote: Wed May 18, 2022 11:44 am Hello FreeCAD community,

I'm in the PartDesign module and want to mirror a pocket along the x AND the y axis at the same time (point reflection through the center)
PartMirror doesn't have that option so I tried Multitranform. But Multitranform keeps the in-between steps. So at the and I have three pockets: The original, the one mirrored around X and the one mirrored around XY.

What can I do?

...
Hmm...it is probably obvious, but I've not had much coffee as yet today... 8-)

I'm having trouble picturing what exactly "point reflection through center" means.

Can you provide an image (hand drawing, or link to something) that is an example...
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
Haavard
Posts: 217
Joined: Wed Feb 17, 2021 10:48 pm

Re: PartDesign: Mirror along X and Y / Point Reflection / Multitranform but only keep result

Post by Haavard »

Create a reference plane angled 45', and mirror the pocket to that?
thomas-huber
Posts: 13
Joined: Wed Jan 26, 2022 4:02 pm
Location: Oberneukirchen, Bavaria

Re: PartDesign: Mirror along X and Y / Point Reflection / Multitranform but only keep result

Post by thomas-huber »

I mean something like this:

Image

I found a solution myself in the meanwhile:
I used the PolarPattern and just rotated the pocket around the center. Still I'm interested if this is the common approach for this
thomas-huber
Posts: 13
Joined: Wed Jan 26, 2022 4:02 pm
Location: Oberneukirchen, Bavaria

Re: PartDesign: Mirror along X and Y / Point Reflection / Multitranform but only keep result

Post by thomas-huber »

Haavard wrote: Wed May 18, 2022 11:58 am Create a reference plane angled 45', and mirror the pocket to that?
That sounds like a good idea. I tried to use a line as reference not a plane. I couldn't reference a line so I gave up on that
User avatar
Shalmeneser
Veteran
Posts: 9475
Joined: Wed Dec 23, 2020 12:04 am
Location: Fr

Re: [Solved] PartDesign: Mirror along X and Y / Point Reflection / Multitranform but only keep result

Post by Shalmeneser »

Central symmetry or Point reflection is just a particular Rotation (+/-180°).
edwilliams16
Veteran
Posts: 3112
Joined: Thu Sep 24, 2020 10:31 pm
Location: Hawaii
Contact:

Re: [Solved] PartDesign: Mirror along X and Y / Point Reflection / Multitranform but only keep result

Post by edwilliams16 »

Any rotation is equivalent to the product of two reflections.

In 2D, sequential reflections of any point about two lines through the origin creates a rotation of the point by twice the angle between the lines.

In 3D, sequential reflections of any point in two planes through the origin creates a rotation of the point by twice the angle between the planes about the axis defined by their intersection.

This all generalizes to n dimensions, but is much harder to visualize. This equivalence is the ultimate source of the various expressions for rotations that involve half the rotation angle, whose existence would otherwise be quite puzzling.
Post Reply