Macro to compute center of mass

[PrzemoF]

I changed version of FreeCAD & updated your macro - now works. It was not finding any materials - only custom & default were available, but no calcs were performed. Thanks!

[schupin]

I just add a new button to automatically change the color of shapes depending on the density indicated :

colorify_1.png (161.6 KiB) Viewed 1758 times

It might help on big model to identify materials.
(maybe it already exists on the BIM workbench, I didn't look at it...)

[Syres]

Thanks for the update and the colours should prove helpful. Just for info I had to change line 27 to:

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__Icon__ = 'https://www.freecadweb.org/wiki/images/4/41/Macro_CenterOfMass.png'

in order to stop this error :

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<unknown exception traceback><class 'SyntaxError'>: ("(unicode error) 'utf-8' codec can't decode byte 0xb3 in position 27: invalid start byte", ('E:/Data/FreeCAD/Macro/CenterOfMass.FCMacro', 126, 4, None))

I'm guessing there's a non-English character in there causing the error.

OS: Windows 7
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16079 (Git)
Build type: Release
Branch: master
Hash: 6363c90a20b296ab69d7b52230009928199d90df
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedKingdom (en_GB)

[schupin]

Thanks for the feedback, I'm always struggling with unicode issues...

I've to check some other things, it seems that it doesn't download icon files while using the addon manager.

[schupin]

I looked at the video here : https://www.youtube.com/watch?v=nKZuiw2DVZ8 and tried to do the same exercice using the center of mass macro.

It worked pretty well :

Question5.png (61.23 KiB) Viewed 1500 times

I also continue the test through the question 6 and 7 using A2plus :

Question7.png (151.88 KiB) Viewed 1500 times

I'm pretty pleased to see that FreeCAD tools are dealing perfectly with this "standard" SW exercice:)

[hds]

Thanks for this macro and i'am using it currently to get the COM of my VIIC. Two issues i did find though but maybe it is just me beeing to much oldschool and not OO compatible ...

1) There might be a bug within the polar array calculation. The macro does not step through the solids in the array but it occurs to me that it takes the center of rotation as the center of mass which is not necessarily coincident.

Center of mass when calculated on array:

CenterOfMassWrong.png (126.3 KiB) Viewed 1392 times

Center of mass with dicretes solids:

CenterOfMassCorrect.png (148.12 KiB) Viewed 1392 times

2) With FC 0.19 at least on my screen the height of the output lines and buttons collapses to be barely visible. I changed the calculation of the COM Popup to be in % of screen height and introduced a few global variables including the output height. Not sure if this is elegant or whatever.

CenterOfMassCollapsed.png (145.31 KiB) Viewed 1392 times

OS: Ubuntu 18.04.2 LTS (XFCE/xubuntu)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.
Build type: Release
Python version: 3.6.7
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)

[UR_]

... height of the output lines and buttons collapses to be barely visible...

Seems to be a Ubuntu "feature"

Annotation 2019-05-21 090429.png (60.67 KiB) Viewed 1384 times

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.16810 (Git)
Build type: Release
Branch: master
Hash: fc37053210d2abc058c6e14b06d7b8e28aeee8ea
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)

[hds]

Around line 300 this patch seems to work. But i'am not 100% certain. May be a professional could have a closer look at it.

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            #2: an array is selected
            if hasattr(sel[sol], 'ArrayType'):
                if sel[sol].ArrayType == 'polar' and sel[sol].NumberPolar > 0:
                    # self.centerofmasses[sol] = sel[sol].Center
                    self.centerofmasses[sol] = FreeCAD.Vector(0,0,0)
                    for hds_sol in sel[sol].Shape.Solids:
                        self.centerofmasses[sol] += hds_sol.CenterOfMass
                        #print(hds_sol.CenterOfMass)
                    self.centerofmasses[sol] /= sel[sol].Shape.Solids.__len__()
                else:

COMpatched.png (152.58 KiB) Viewed 1347 times

[hds]

just found that for multiple arrays or clones thereof there needs to be an additional patch around line 276:

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            # Find the center of mass depending of the type of object.
            if hasattr(objs[sol], "CenterOfMass"):
                self.centerofmasses[sol] = objs[sol].CenterOfMass
            elif hasattr(objs[sol], "Solids"):
                    # self.centerofmasses[sol] = objs[sol].Solids[0].CenterOfMass
                    self.centerofmasses[sol] = FreeCAD.Vector(0,0,0)
                    for hds_sol in objs[sol].Solids:
                        self.centerofmasses[sol] += hds_sol.CenterOfMass
                    self.centerofmasses[sol] /= objs[sol].Solids.__len__()
            #estimate cdg of a mesh
            elif hasattr(objs[sol],"Points"):

MultipleArraysClones.png (124.46 KiB) Viewed 1326 times

[schupin]

Thanks a lot for your corrections HDS !

I hope it will help your boat to float

I'll investigate on your graphic bug : I'm on ubuntu (kde), the Freecad-Daily works well.

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OS: Ubuntu 19.04 (KDE/plasma)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.
Build type: Release
Python version: 3.7.3
Qt version: 5.12.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: French/France (fr_FR)

Seems you have an older version of Qt than me (but younger than UR_).

I'll take a deeper look.