# Repetitve subtraction **URL:** \ **Category:** SketchUp\ **Created:** [February 9, 2020, 9:55pm UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851 "2020-02-09T21:55:56Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![bwana](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/bwana/32/20446_2.png) [@bwana](https://forums.sketchup.com/u/bwana)\ **Post date:** [February 9, 2020, 9:55pm UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/1 "2020-02-09T21:55:56Z")
I have a sphere and a bunch of pyramids that looks like this: ![pyr4-2](https://global.discourse-cdn.com/sketchup/original/3X/c/9/c91b016e5f40c33abe95e703b8eda488f5784c29.jpeg) I want to subtract the pyramids from the sphere. I made the pyramids into a group and tried to subtract the group from the sphere but sketchup says I need two solids. TWO SOLIDS ONLY. ![Untitled](https://global.discourse-cdn.com/sketchup/original/3X/7/5/75ae6f8111fa393d559b7df8eed27180c15c38af.png) so i ungrouped the cluster of pyramids and started subtracting each pyramid from the sphere like so: ![pyr4-3](https://global.discourse-cdn.com/sketchup/original/3X/6/1/619b69a99036ca928d739138680975616b877217.jpeg) Isnt there a way to subtract all the pyramids from the sphere at once? ---
**Author:** ![DaveR](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/daver/32/7601_2.png) [@DaveR](https://forums.sketchup.com/u/DaveR)\ **Post date:** [February 9, 2020, 9:59pm UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/2 "2020-02-09T21:59:28Z")
What version of SketchUp are you using? Please complete/update your profile. Upload the model so we can see exactly what you are working with. ---
**Author:** ![bwana](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/bwana/32/20446_2.png) [@bwana](https://forums.sketchup.com/u/bwana)\ **Post date:** [February 9, 2020, 10:15pm UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/3 "2020-02-09T22:15:00Z")
how/where do i upload the model? BTW, I can start w a bunch of pyramids and start subtracting them one by one from the sphere ok. But if I try and save my work, sketchup complains that there is a problem and it wants to fix it. If I fix the problem, save , quit, and reopen then it will not allow me to continue my work-rather it gives me the error dialog pictured in the second image above. ---
**Author:** ![DaveR](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/daver/32/7601_2.png) [@DaveR](https://forums.sketchup.com/u/DaveR)\ **Post date:** [February 9, 2020, 10:16pm UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/4 "2020-02-09T22:16:36Z")
> [@bwana](#): > > how/where do i upload the model? Same way you uploaded the image. > [@bwana](#): > > sketchup complains that there is a problem and it wants to fix it. If I fix the problem, Probably due to the dimensions of the model. ---
**Author:** ![MikeWayzovski](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/mikewayzovski/32/98346_2.png) [@MikeWayzovski](https://forums.sketchup.com/u/MikeWayzovski)\ **Post date:** [February 9, 2020, 10:47pm UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/5 "2020-02-09T22:47:10Z")
Select all the pyramids, explode them and while still selected immediately make a group Then perform the solid action ---
**Author:** ![colin](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/colin/32/266703_2.png) [@colin](https://forums.sketchup.com/u/colin)\ **Post date:** [February 10, 2020, 12:52am UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/6 "2020-02-10T00:52:58Z")
My attempt (I replaced the model, wasn’t sure what the end result is supposed to be like, so I did a couple of variations). [pyramids.skp](https://forums.sketchup.com/uploads/short-url/1Ac6JhanJ51AygBtUkkjYT5eVbK.skp) (671.0 KB) ![pyramidholes](https://global.discourse-cdn.com/sketchup/original/3X/4/8/483eeb0b81086ab1ca493b73355a2733c83931d2.png) ---
**Author:** ![bwana](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/bwana/32/20446_2.png) [@bwana](https://forums.sketchup.com/u/bwana)\ **Post date:** [February 10, 2020, 3:48am UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/7 "2020-02-10T03:48:06Z")
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: ![pyr4](https://global.discourse-cdn.com/sketchup/original/3X/3/c/3cbeb0010e98343ec2b104a030b074a0f63f5e98.jpeg) 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](https://forums.sketchup.com/uploads/short-url/hTJOpXctS1l1mgjsqnOTrMuAquE.skp) (3.3 MB) ---
**Author:** ![bwana](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/bwana/32/20446_2.png) [@bwana](https://forums.sketchup.com/u/bwana)\ **Post date:** [February 10, 2020, 4:06am UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/8 "2020-02-10T04:06:56Z")
I went back to the beginning and created a simple hollow sphere. I then subtract a few pyramids from it one by one. But then, I noticed my sphere wasnt hollow any more but each cavity made by a pyramid subtraction left walls in the channel. I then have to delete each individual wall-way too much work. ![pyr4first](https://global.discourse-cdn.com/sketchup/original/3X/0/4/04e459a4e9a6e8b0de4076352a57881ff67e3de0.jpeg) It looks a little like the spaceship from 2001 A space odyssey. Here is the model [pyr4first.skp](https://forums.sketchup.com/uploads/short-url/lnUzh1znVVzHo2TxxtfNfPFuxMx.skp) (2.0 MB) ---
**Author:** ![colin](https://sea2.discourse-cdn.com/sketchup/user_avatar/forums.sketchup.com/colin/32/266703_2.png) [@colin](https://forums.sketchup.com/u/colin)\ **Post date:** [February 10, 2020, 5:00am UTC](https://forums.sketchup.com/t/repetitve-subtraction/115851/9 "2020-02-10T05:00:20Z")
I did a screen recording that also shows how I did the pyramids using built in tools. You should watch the dimensions box, that’s where a lot of what I did goes on. When the sphere disappears it’s because I cut it, to paste in place later on. I used keyboard shortcuts quite a bit, one of which is a custom one. I have ctrl-shift-z to Zoom Selection, it’s very handy. All done using my MacBook Pro trackpad. For the moment going to YouTube will show better quality. I expect it will look better here later on. [![](https://global.discourse-cdn.com/sketchup/original/3X/d/3/d365f0f8063420bbe336fb1512260d79b2904fec.jpeg "Holes in a sphere from 100 pyramids") ](https://www.youtube.com/watch?v=kSJxY8NLJc0)