blender – A Geeky Gulati

Using blender to make 3D font thingies to print at Shapeways

Posted in a how-to video here:

[youtube=https://www.youtube.com/watch?v=muMX3byfJ9o&w=448&h=252&hd=1]

0:00 Intro
0:49 Choosing a Font
1:06 Blender the inadequate Intro
2:00 The “Fast” route that doesn’t always work
6:07 “Reliable” way
9:40 Deleting Inner Shells
10:43 Exporting to Shapeways via OBJ – No Texture
12:00 UV Mapping, Texture
15:31 Exporting to Shapeways via X3D – With Texture

Having now finished the video, it occurs to me that using a picture as texture would work very well with cylindrical or spherical mapping.

While in this video I’m focusing on printing at Shapeways, its possible to print at home – just export to STL. However, Shapeways uses a different process which allows for filler material which makes supports a lot easier for this kind of complexity, compared to the FDM process I would use at home on my Solidoodle.

Video captured using Open Broadcaster Software; edited down using Premiere Pro.

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.

From PhotoScan to Shapeways: 1/N – Using Blender as an intermediary

Shapeways is one of several print services that offer full color prints – something I cannot afford myself. However, they do not allow on-site scaling – you have to scale the model yourself. There are also various cleanup steps that have to happen before shapeways will print your model. For these I use blender. (ref: shapeways page on blender editing)

Scaling, then Lighting, then Checking for Problems

Blender does not (by default) understand units of measurement; however during import, shapeways will ask what the unit is. I go with mm; I want the model to be up to 50mm in size.

The original is starting out at (Dimensions) 0.972 (assumed mm) as its largest dimension. If I scale it up by 50, I get 31 x 48 x 40 instead. Then, very important: apply scale so that the XYZ coordinates are actually changed (some tools, like solidify, work before scaling – used for hollowing out an object).

Side note if you want to check textures: A this point, the model is a bit dark as the original light is now inside the model, and not quite bright enough. I usually find and drag the Lamp gand drag it out into the open, and give it a distance for falloff of 3000 and more energy.

And now the fun part! Turn on the 3d printing tools (via extensions), and … don’t believe everything. But do check for minimum wall thickness of 2mm. and.. ouch. A lot of stuff. Now, Shapeways may not complain about all of this – you are always welcome to upload. In fact, I’m doing just that, to see what they will come back with.

Shapeways

False End #1: Do not export as .OBJ. Shapeways does not process the .MTL and the .PNG file, and you get no color. Instead, try .X3D.

If you open the .x3d with a large-text-file editor (like notepad++, or even in blender), you’ll find that it has a reference to a texture file with a different name:

Be aware of it – zip both the .png and the .x3d file into a .zip file for upload to shapeways.

After the file uploads and gets processed (30 seconds?), you get this screen:

And if I scroll all the way down, to the interesting stuff – Full Color Sandstone:

First, $23.13 .. OUCH. Second, Thin walls. It’s a link. Follow the link.

As you can see, this is not the sea of yellow that we saw earlier. But, it also has this “Fix Thin Walls” button.

Oh my, we gave Dan the pox. Well, no big deal, lets print that anyway …

But now we have lost color. No deal. Back to fixing wall thickness in blender (and reducing the size of the model!)

Photoscan: Using Blender as an intermediary touch up tool

I’m glad that I have a solution (use a good camera and lens) for capturing 3D models – but I’m still trying to get the process matured – to the point where I could run a scan-and-print booth at a flea market. (not that I’m going to; I’d just like to be that good at it).

The Problem: No Noggin

This is a DSLR Dan Scan with a Medium Dense Point cloud on Moderate (Ultra high didn’t really add to the detail). The top of the head is missing, and there’s a large seam in the back that is not filled. Also, the bottom isn’t a good base for a printed model.

The Solution: Blender!

It is important to leave the model where it comes in – I have to export it at that exact spot in order for Photoscan to pick it up. Luckily, I can select the object and zoom to it using “.” on the keyboard. (Blender: shortcuts keys are dependent on which window is active, it has to be the 3d window for . to work)

I then remove stuff from the model, and add in some more surfaces (NURBS surface shown here), to get the model closer to what I want:

a b c

d e f

a: I use perspective + border select + delete vertices to clear away an even cut which I will augment with a surface.
b,c: I create (separate object) a NURBS surface with “Endpoint=UV”; I fit the outer borders first (so that there is a little gap showing) and then move the inner points (how much it sticks out) in; I try to ensure there’s always a gap between the actual model and it (easier to join later)
d: For the base, I create a square (cylinder would have been better?), move the edges in, and then delete the top surface. I subdivide till it has the right “resolution”.
I then convert NURBS to meshes; select the meshes; subdivide them to match resolution, and join them everything into a single mesh.
e: Sometimes to avoid “helmet head” effects, I have to delete some of the edge faces of the former NURBS by hand.
f: Stark from Farscape.

Another touch-up I can do in Blender is to smooth skin surfaces using “Scuplt”:

Wrapping it up

I have to join the pieces together by hand *somewhere*, so that the holes have boundaries. Try to keep each hole in 1 axis. Notice how I subdivide the larger mesh so that the points line up. Don’t forget to Normalize faces outward when done.

I can then export the .OBJ back to disk, and in to Agisoft Photoscan, where I finish the hole-filling process. (I’ve tried filling the holes in blender, but I run into vertex normalization / faces being inverted problems.)

And then, we can build a texture, and Dan’s noggin won’t be left out.

And Now for Something Completely Different:

The other direction to go is to use a completely different mesh and see what happens:

suzanne the monkey:

sphere scaled to head shape:

We could also do a Minecraft version of Dan – by joining several rescaled cubes, and then building a texture around that. That would make for an excellent Pepakura model. However, I’m out of time on this blog post (1h24m so far), so I’ll save that for another day.

(after editing: 1h40m taken)

Freakin Holes

This is my part in NetFabb. Its Fine.

This is my part in Blender with Select NonManifold. its Fine.

This is what Repetier Host and Slic3r 0.99 think of my part. They are not fine.

Following the Trail

Loading the part up in blender, translating it by the X Y Z indicated in Repetier host, and then putting the 3d cursor at the specified coordinates:

Nothing suspcious? Rereading: it said “near edge”, so there should be an edge between those two locations. Because the X and Z stay constant, its along the Y axis. So it must be one of these guys:

Aha – I think I found it. There’s actually several vertices here. Ctrl-+ a few times to grow selection, Shift H to hide unselected, and then move some stuff around.

Delete the vertex, look for holes and fix:

Send it back over to slicer, and try again:

Not winning today.

Update: didn’t seem to have any problems with slic3r 1.01. Now I have to figure out how to configure Repetier Host to talk to a new slic3r install on the computer. (Update: very easy. Tell RH which directory slic3r lives in, and it handles the rest).