Silhouettes can be used to mark and measure ‘closed surfaces’ or volumes. However, the photography for modeling silhouettes differs somewhat from the photography for a regular points-based project.
You’ll see in the Help file silhouette example the 2 photos for the mouse project are taken from directly above the object and directly from the side, which allows the solid shape to be shaped correctly (imagine the light rays shaving the volume to size and shape from a given camera angle through the silhouette photo marks). Again, the silhouette photo requirements are quite specific about this.
This is from the Help file in the “To create a Silhouette Surface” section:
“Take photographs of the object trying to ensure that every plane of the surface is in a photograph that is perpendicular to that part of the surface. In other words, try to photograph every surface
”edge on” in at least one photograph.”
So you may need to add photos to your project to more suitably mark the silhouette. Note that standard photos are required for orientation and modeling other features (eg points and lines) but for the silhouette you’ll want to mark it on additional photos at perpendicular camera angles for better results.