Subtract

Regions of a volume can be removed using the Subtract option.

1. Select the Geology workflow tab
2. Select at least two geometry volumes or one volume and one surface. All volumes must intersect each other to be able to subtract any volume. If you select one volume and one surface, ensure the surface cuts through the entire volume. Ensure the entire Entity is selected for each added volume or surface.
3. Select Geometry > 3D Boolean > Subtract in the menu or click on the Subtract icon in the toolbar.
4. A dialog should appear to allow you to select the Volume to Split and the Splitter used to calculate the region to remove from the volume to split. You can modify the volume to split and the splitter using the drop down menu.
5. For two selected volumes it is relatively straight forward to visualize the volume of the splitter that is removed from the volume to split.
6. For one selected volume and one surface, the volume removed is based on the direction of the surface normals. Each plane section of a surface has a plane normal, which should all be oriented so that one side of the surface is the positive side (the side the normals are pointing towards) and a negative side (the side the normals are pointing away from). The volume that is on the negative side of the plane normal is removed. You can try this by drawing a volume and a plane that fully cuts through the volume. Try using the Subtract tool and then rotating the surface 180 degrees and trying it again.