The 3D files from the Structure scanner often have holes and unwanted geometry. After following this guide you'll get a watertight model that is ready for (colour) 3D printing. A basic understanding of mesh manipulation in Blender is necessary. This guide uses Blender, but here is a guide that describes this process for Meshmixer.
The structure scanner delivers the 3D object in 3 parts:
Model.obj
is the 3D objectModel.jpg
is the texture fileModel.mtl
is a file that links the object to the texture.
You only have to open the .obj
file. The program will find the other files on its own:
File > Import > Wavefront (obj)
. Choose the .obj
fileleft mouse click
Set Origin > Geometry to origin
.
The scan data coming from the Occipital Structure sensor isn't yet joined in a single mesh. It consists of multiple sections that overlap on the edges. To test this, hover the cursor over the object and go to Select > Select Linked > Linked
(Shortcut: l
) (lower caps L). This selects all vertices that are linked. As you can see, only a single section is selected.
Select > All
(shortcut: a
).Mesh > Clean Up > Merge by Distance
. The default distance should do.Mesh > Normals > Reset Vectors
The 3D print add-on for Blender is helpful in preparing your object for 3D printing: enable the add-on 3D-Print Toolbox
in the Blender preferences.
Cut away unwanted parts, like the surface the model was standing on.
Delete loose parts
Select > None
(shortcut: alt + a
).l
(lower caps L).Select > Invert
(shortcut: cmd + i
)Mesh > Delete > Vertices
(shortcut: x > Delete Vertices
)The 3D scanner generates a mesh with messy topology. There are areas with very large faces, and others where there are lots of vertices crammed together. This creates visible stress points in the mesh. The relax function moves the vertices away from densely populated areas in order to be more equally distributed. Having the mesh relaxed will prevent a series of problems later on. This will change the shape of the mesh a little bit though.
a
Vertex > Relax
. A single iteration will do.Fill tiny holes by merging vertices together. This way the texture will stay visible.
left mouse button
shift + left mouse button
Vertex > Merge Vertices > At Last
(shortcut: alt + m > Merge At Last
).l
(lower caps L) to select and then delete all linked vertices.New faces added to the mesh appear black or show random colours. They are referencing meaningless parts of the texture. Let's project the selected vertices to the texture and clone the surrounding texture onto that area.
UV > Unwrap
(shortcut: u > Unwrap
).Ctrl + left mouse click
(the 3D cursor will indicate the position). Now you're ready to draw.
When the holes are big, closing them with Vertex > New Edge/Face from Vertices
(shortcut: f
) results in a flat surface that interrupts the flow of the shape. Here are two ways to reconstruct the natural curve of the object. Clean up the edge of the hole as described above.
Face > Grid Fill
.
Both versions aren't perfect. Mesh stress areas are marked with the red circles.
Clean up dark spots by resetting the normal vectors:
Mesh > Normals > Reset vectors
Clean up visible edges with the smoothing brush in the Sculpting workspace.
This is more tedious, but it allows for better control over the shape .
Vertex > New Edge/Face from vertices
. (shortcut: f
) to fill the gap with a single n-gon. Vertex > Connect Vertex Path
(Shortcut: j
). This will not create overlapping faces, but instead divides the current n-gon in half. The new vertex path will include any edge it runs through. This method allows you to define the new surface in steps, going from a rough definition to fine surface details.
Tips:
Vertex > Slide Vertices
(Shortcut: shift + v
or double tap g
)Mesh > Delete > Dissolve …
(shortcut: ctlr + x
) This way you keep the existing faces intact instead of making a hole. Retexturing is the same as described above.
Mesh > Normals > Recalculate Outside
(Shortcut: shift + n
).Mesh > Normals > Flip
.
Show the face normals for a visual check. In Edit mode: Overlays > Enable face normals
.