I'm trying to perform a boolean difference to cut a piece out of this treasure chest lid to change to a pop-in hinge: The model is an STL from Thingiverse. I created a shape that I want to cut out of the lid in Fusion360, exported it as an STL, and imported it into Blender: I lined them up in Blender and then added a boolean difference modifier to the treasure chest lid, setting the cutting shape as the object to subtract. Instead of cutting a piece out of the lid, it looks like it performed a union instead: The original cutting shape is hidden, so what is visible here is the result of the operation. It looks like it unioned the two shapes.
I checked all the common reasons for problems:
- Normals - Normals look fine when I show them. To be safe I opened each object in edit mode and did
Mesh > Normals > Recalculate Outside. No change.
- Duplicates - I attempted to eliminate duplicate points using
Mesh > Clean Up > Merge By Distancefor each object. No change.
- Non-Manifold Geometry - When I go to
Select > Select All by Trait > Non Manifold, nothing is selected for either object.
What else could be causing my boolean difference to fail? What can I do about it?
Here's a Dropbox link to the Blender file.