CSG

The basic operations of constructive solid geometry (CSG in short) are union, intersection, difference.

Union

We have already seen how to make a compound object. This corresponds to the union and you can use it in CSG constructions.

Intersection and difference

The difference of A and B is defined by amputed_by. The intersection is defined by intersected_by Note that the cutting shape may mark the amputed object with its color depending on the options.

By default, when A is cut by B, B is glued on A so that when you move A , the hole that you made will not move relativly to A (a hole in the center remains in the center for instance).

wall=Cube(2,2,2).colored("Brown").translate(origin-X-Y+.5*Z) # the cube is moved above the plane

cyl=Cylinder(start=origin,end=origin+5*Z,radius=0.5).colored('SpicyPink')

axis=Segment(point(0,0,0),point(0,0,1))
cyl2=ICylinder(axis,0.25).colored('Yellow') #an infinite cylinder 


# Using amputations : corresponds to the yellow and pink marks since the elements amputed don't keep their textures
cyl.amputed_by(cyl2,keepTexture=False,takeCopy=False)
wall.amputed_by(cyl,keepTexture=False,takeCopy=False)

# Using intersection : no change of colors since keepTexture is true by default.
axis.translate(3,0,0)
cyl3=ICylinder(axis,3.2).colored("Green")
axis.translate(-6,0,0)
cyl4=ICylinder(axis,3.5).rgbed(1,1,1)
wall.intersected_by([cyl3,cyl4],takeCopy=False)
wall.rotate(Segment(origin,Z),.5)

In the above, we put

camera.filmAllActors=True

Nevertheless, the cylinders used to cut the cube do not appear. The reason is that the tool used to cut is declared invisible. By default, in A.amputed_by(B), B is not seen, does not follow when A is moved, does not impose its texture/color

The general syntax with the possible options is:

A.intersected_by(cuttingShape,throwShapeAway=True,keepTexture=True,takeCopy=False,glued=True)
A.amputed_by(cuttingShape,throwShapeAway=True,keepTexture=True,takeCopy=False,glued=True):

The intersection and difference is not recursive, ie. does not include the children. To intersect A with B and its children:

for tool in B.descendants_and_myself():
  A.intersected_by(tool)