Boolean null and universal sets

[AdrianBowyer]

A feature request.

When writing Python to build shapes it'd be very useful to have the Universal and Null sets available in the Part API. (I suspect these are already used internally.) Then one could write:

Code: Select all

a = Part.Null()
for i in range(0, n):
 a = a.fuse(MyShapeThatDependsOnN(n))

or

Code: Select all

a = Part.Universal()
for i in range(0, n):
 a = a.common(MyShapeThatDependsOnN(n))

Both would also be useful in conditional code:

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a = SomeShape()
if n > 0:
 b = MyShapeThatDependsOnN(n)
else:
 b = Part.Null()
a = a.fuse(b)

[Kunda1]

bumping this for more disussion

[wmayer]

Part.Shape() delivers the null shape. A universal shape doesn't exist, only a half-space solid is supported by the kernel.
The best what you can do to have a universal shape is creating a sphere with a very high radius:

Code: Select all

Part.makeSphere(1e10)

[AdrianBowyer]

Part.Shape() delivers the null shape. A universal shape doesn't exist, only a half-space solid is supported by the kernel.
The best what you can do to have a universal shape is creating a sphere with a very high radius:

Code: Select all

Part.makeSphere(1e10)

Sadly that doesn't work. The first piece of code in my original post then gives the error:

<class 'Part.OCCError'>: Base shape is null

[AdrianBowyer]

Sadly that doesn't work. The first piece of code in my original post then gives the error:

<class 'Part.OCCError'>: Base shape is null

I use this to make the null set, which is horrible, but which works:

Code: Select all

def NullSet():
 a = Part.makeBox(1, 1, 1)
 a.translate(Base.Vector(10, 10, 10))
 return a.common(Part.makeBox(1, 1, 1))

[Kunda1]

Sadly that doesn't work. The first piece of code in my original post then gives the error:

<class 'Part.OCCError'>: Base shape is null

I use this to make the null set, which is horrible, but which works:

Code: Select all

def NullSet():
 a = Part.makeBox(1, 1, 1)
 a.translate(Base.Vector(10, 10, 10))
 return a.common(Part.makeBox(1, 1, 1))

Hello @AdrianBowyer, It's excellent to see you on this forum! Just a quick question, what version of FreeCAD are you using? (please copy/paste About) Thanks!

[AdrianBowyer]

Hello @AdrianBowyer, It's excellent to see you on this forum! Just a quick question, what version of FreeCAD are you using? (please copy/paste About) Thanks!

OS: Ubuntu 20.04.2 LTS (ubuntu:GNOME/ubuntu)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.19.2)
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.8
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: C/Default (C)

[wmayer]

git commit 666f67f8d9

Allows you to write:

Code: Select all

a = Part.Shape() # Null shape
b = Part.makeBox(1,1,1)

c = b.cut(a)
c.isNull()

c = a.cut(b)
c.isNull()

c = a.fuse(b)
c.isNull()

c = b.fuse(a)
c.isNull()

c = a.common(b)
c.isNull()

c = b.common(a)
c.isNull()

[AdrianBowyer]

Hi!

That doesn't work, I'm afraid. It gives a

<class 'Part.OCCError'>: Base shape is null

error, by which it means the shape is undefined. The CSG null set is a perfectly well defined shape - empty space.

[wmayer]

Have you built the latest version that includes these changes?