Thank you colin. Yes I tried to make the sphere with windows cut out of it. This is an attempt at reverse projective geometry. A grid on a plane projected into the center of a sphere. I tried to reproduce what you did. Here is a pic:

On the left is the assembly of pyramids I want to subtract from the sphere.

The next three images show the construction of the hollow sphere. Basically I create an annulus first. Then I create a circle orthogonal to it. Then I click on the circle, click follow me tool, and then click on the annulus to get the hollow sphere.

Finally I move the sphere into position but for the life of me cannot figure out how to subtract the pyramids from the sphere. I keep getting the ‘not a solid’ error dialog. Attached is the model I have. I downloaded your model and yes it is very close to what I am trying to achieve. Interestingly, when I move the viewpoint into the middle of your sphere, nothing is visible outside

.pyr4.skp (3.3 MB)