Cutting Shape from Solid Object

Hello everyone!

I need to cut a piece about 1/4 of and inch
from a solid object. What is the correct tool to cut from a solid object and control the thickness of the cut? But I need to keep that cut piece and not delete it.

Think of it like cutting a shape out of the big piece of jello. But I don’t want to cut all the way through, I need to control the cut thickness.

Thanks for any advice!

Hi Landia - you’ll need to make an object(s) that represents the thickness of the cut - two parallel surfaces, say. Then the command to use is BooleanSplit.

CutWithThickness.3dm (238.6 KB)


Here is an example I just created:

I created the oval shape above the sphere. I wanted to project the oval shape on top of the sphere and cut it out but keep the oval shape. I did it before but can not remember what tool I use. You just highlight the oval shape and command it to project down on the object and you can control the cut depth. Like cut 1/4 of an inch into the surface of the sphere.

I think you are on the right path.

Hi Landia - Extrude the oval shape through the sphere, and then BooleanSplit …does that get what you need? Or from the Top view just Split the sphere using the curve. A little different result.


Ah. ok - then Extrude it that far - then BooleanSplit. If the bottom of the cut needs to be spherical as well, then you need a little more work - hang on a bit.
BooleanSplitExample.3dm (388.8 KB)


Hi Pascal.

That is it! You found the answer to what I was looking for. But how did you get the oval shape to lay on the surface of the sphere? What is the command to lay the oval shape on the surface of the sphere so I can do the BooleanSplit?

That is correct, the bottom of the cut needs to be spherical as well. If you can help me to lay the oval shape on the surface of the sphere, I can Extrude it to the depth I want.

Hi Landia - the part that labeled BooleanDifference cuts the inner sphere from the extruded ellipse. See how that shape is then correct for BooleanSplit on the outer sphere.


Is there a way to lay the TOP oval shape around the surface of the sphere? Like project the oval shape right onto the surface of the sphere? The sphere is just an example of what I am trying to do. But here is what I am really trying to make:

I am trying to create a headlight cover for a car. I need to cut a shape out from the main body of the car and make it into the headlight cover. I need that cut piece so I can apply Glass material.

Hi Landia- the Project command should do what you need. Split the target surface with the curve and then OffsetSrf, Solid=Yes. Are we getting close?


Thanks Pascal!

The Project command is perfect for what I was looking for.

Hi Pascal.

Last question. When I did the OffsetSrf command, I lost the top piece of the oval shape. But the OffsetSrf command is a great feature but it did not save the top oval shape. How do I get the top oval shape?

As you can see from the picture, I got the oval shape cut out from the sphere but the oval shape piece is gone and I need that oval shape.


You only lost that part when you did a BooleanDifference, right? [I don’t see why the OffsetSrf would do that.]

You should either:
offset the ellipse before projecting, splitting, and offsetting the resulting surface and use that to boolean cut into the sphere

first do the boolean difference without deleting the input. Then explode the cutting object, offset the edge of the upper surface, trim that surface with the new curve, and OffsetSrf the resulting surface.

Hi Wim.

Before I try your methods. I wanted to try this first. Is there a way to make the oval shape into a solid object and give it a half an inch thickness? The problem is the oval shape is curve and I can not make it into a solid oval shape with thickness.

The oval in the picture is highlighted in yellow. I tried the Solid > Extrude Planar Curve > Straight but it did not work. If there is a way to make that curve oval shape into a solid with a thickness, I am all good to go. I can than put it over the sphere and it should fit nicely.

I just got it to work now. Thank you both for your help!

After reading through this, I have what I hope is a useful observation.

@Landia is approaching this modeling exercise from a “solid” point of view, instead of from a “surface” point of view.

Rhino is a surface modeler that can make solids. You do this by making surfaces the right shape and location that can be cleanly Joined and enclose volumes.

Maybe that will help as you approach future modeling tasks.

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Thanks John!