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I have a scene where I need to be able to "interactively" cut a mesh. I have set up a bounding box, and the object I need to cut is set inside. When I move the vertices of the bounding box, the object is cut because of my implementation of a boolean modifier with the "union" property. Here is an example:

However, the sphere is just being flattened in this image. What I need is to be able to literally "cut" the sphere, so that it is hollow on the inside. Is this possible, and how can I do it?

Here is how I want it to look, but with the ability to be animated.

Any help/suggestion is welcomed!

Edit: I added a photo of how I want the image to look.

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    $\begingroup$ See this discussion: blenderartists.org/forum/… (Bisect as modifier?) $\endgroup$
    – CodeManX
    Commented Jan 27, 2014 at 1:42
  • $\begingroup$ Could you add an image of how you want to look? I'm not sure what you mean by "hollow". $\endgroup$
    – gandalf3
    Commented Jan 27, 2014 at 4:09

3 Answers 3

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You could add a solidify modifier to the sphere before the boolean modifier:

enter image description here

Also note that you can set the boolean modifier to Difference and use a plane as the Object, it may be easier to animate than a cube.

For this to work, the normal of the plane must be facing the sphere:

enter image description here

You can flip the direction of the normals by

  • Pressing Flip Direction in 3D view > Tool Shelf (N) > Basic > Normals

  • Pressing CtrlN and enabling Inside in the Redo menu (either at the bottom of the Tool Shelf, or by pressing F6).

Result:

enter image description here

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  • $\begingroup$ If the plane is "cutting" through the Sphere, shouldn't the plane have the Boolean modifier set to Intersect? When I try your solution nothing happens, the plane and sphere are both visible and no clipping of the sphere happen (checked normals, applied scale etc) $\endgroup$
    – MicroMachine
    Commented Dec 13, 2018 at 20:05
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    $\begingroup$ @MicroMachine With the new bmesh solver it seems using an open plane doesn't work consistently (I've reported a bug about it here). In the meantime you can use carve on 2.7x or a closed mesh (such as a cube) in 2.8. $\endgroup$
    – gandalf3
    Commented Dec 14, 2018 at 8:48
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If not animated:

Edit mode

Menu: Mesh > Bisect

Click and select options at left (T tools panel in 3D View), like fill or quit parts. Get it from: http://wiki.blender.org/index.php/Doc:2.6/Manual/Modeling/Meshes/Editing/Subdividing/Bisect

The boolean operations always try to conserve the mesh.

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  • $\begingroup$ Thank you for the advice, but I need it to be animated. If you have any more ideas, please let me know! $\endgroup$
    – Lamikins
    Commented Jan 27, 2014 at 2:27
  • $\begingroup$ @Lamikins You can animate the Plane Point values after using the Bisect tool. $\endgroup$
    – iKlsR
    Commented Jan 27, 2014 at 5:51
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    $\begingroup$ No you can't animate operator settings. $\endgroup$
    – Rhys
    Commented Jan 27, 2014 at 9:56
  • $\begingroup$ @Lamikins You could get the parts generated with Bisect and make them separate or hide on the correct time during animation. Perhaps if you explain more about your animation could be more easy help you. $\endgroup$
    – user2266
    Commented Jan 27, 2014 at 10:05
  • $\begingroup$ See my comment to the question, there has been talk about bisect and if it's possible to make it a modifier. But so far, you could only bisect for every frame like suggested by gabrign, which means there will be one mesh datablock for each frame of the animation with no transition in subframes. $\endgroup$
    – CodeManX
    Commented Jan 27, 2014 at 11:32
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You could put a second smaller sphere within the first one with boolean difference.

modifiers

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