From Photoscan to Shapeways: Process 2/N

TL;DR:  Nice idea, but fail.

Holy crunch this is taking a lot of hands on stuff figuring out what works, and what doesn’t.   I decided to step back and take a look at the strength / weaknesses of everybody and see if I could meta a process out of it.

Program	Strengths	Weaknesses
Agisoft Photoscan	Can fill holes; gets normals correct when filling holes Can Export and Import .OBJ Can Export and Import WRL Unique: can create textures from images	Cannot select only visible surfaces for deletion; has to select hidden as well Can only close holes; does not always generate manifold Cannot export STL Cannot resize Import object cannot have been moved
Netfabb	Great job filling holes Can detect non manifold Unique: Very good at making things manifold automatically Import/Export OBJ, STL, WRL Can resize	No direct mesh manipulation Free version cannot remove extra shells
Blender	Unique: Can do union operations to add missing chunks together Can detect non-manifold very well In depth mesh editing Can resize Thin wall detection Import/Export OBJ, STL, WRL Can remove extra shells	Fills holes with akward normals Cannot auto-fix manifold Deleteing faces causes complex manifold problems which escalate quickly
Windows / etc	Can ZIP files	heh
Shapeways	Import texture with ZIP files Thin wall detection Unique: Can print in color!	Cannot directly import multi part objects unless ZIP first Cannot resize Thin wall fixes loose texture Cannot get texture when importing OBJ

Proposed Flow

Agisoft	Generate mesh Save as A.obj Use circle and block delete to remove chunks to be replaced in blender Save as B.obj
Netfabb	Import B.obj Fill holes / clean up / repair Save C.obj
Blender	Import A.obj Import C.obj – should be manifold Create additional surfaces D1,D2 etc to union using A for reference Union them with C <– not sure if this will work every time.  If it works, save as F.obj If unioning does not work, then: Import B.obj Prune surfaces D1,D2 etc so that there is no overlap with B Create faces to join B and D1,D2 etc so that a fill holes will do the right thing Save as E.obj
Agisoft (if stuck at E)	Load E.obj Fill holes Call this F.obj
Agisoft	Load model from F.obj Generate textures Export as G + GT (.obj)
Blender	Start over Load G + GT (.obj) Relocate, Orient Scale, Apply scale Thin wall detect Save as H  + GT (.X3D)
Windows	Zip H+GT to HZ
Shapeways	Upload HZ Look at thin walls situation -> leave open
Blender	Fix thin wall situations (and other problems) Save as I + GT (.x3d)
Windows	Zip I+GT to IZ
Shapeways	Replace with IZ Hopefully can print.

Wow, that’s a lot of steps.   No wonder I’m a bit frustrated.  

Update as of 6/1 (3-4 days after writing this): 

I tried it.  Twice.   5 hours later: It’s a fail.     The reason is that:  When I get to step G->H in Blender – when I do any fixes in blender – if those fixes involve cutting away dead faces and closing holes or anything like that – I loose texture.  As I usually have to do this surgery around places where I filled it in during step C+DN, Its all over the model, and It would look ugly.

However, I did learn a bit about fitting NURBS spheres onto human faces.   You go into Alt-Q 4-way view (Top, right, front), and first fit the edge pieces (where the surface comes all the way out to the control point); before going on to the other bits.  In the case of a human head, the anchor points are:  just above the ears, an imaginary line going back from the chin, just under the nose, etc.    This could be its own blog post, but I’d need more practice to verify that it works well every time. 

Next up I’m going to try a much-reduced polygon count – get rid of some of this detail that causes the thin walls.  The idea would be to use color and texture to make it look like the human.