Blender - Cut With Cube

To split an object perfectly in half using a plane, use the Boolean modifier method with a Cube instead of a flat plane. This prevents "open mesh" calculation errors and ensures both halves remain solid, closed shapes.

Step 1 - Place Your Cube

1. In Object Mode, press Shift + A ➔ Mesh > Cube.
2. Scale and position the cube so one of its faces aligns exactly where you want to split your object.
3. Ensure the rest of the cube completely covers the half of the object you want to separate.

Step 2 - Create the First Half

1. Select your original object.
2. Go to the Modifier Properties tab (blue wrench icon).
3. Click Add Modifier ➔ Generate ➔ Boolean.
4. Set the Operand Type to Object.
5. Set the Operation to Difference.
6. Use the Eyedropper tool to click and select your cutting cube.

Step 3 - Duplicate and Create the Second Half

1. Press Shift + D to duplicate your object, then right-click immediately so the copy stays in the exact same position.
2. Select this new duplicated object and look at its Boolean modifier.
3. Change the Operation from Difference to Intersect.
4. Hide your cutting cube (H) to see the results.