Plug-in features for 3-d print modeling

[jentron]

Lately I've been thinking about some features it would be great to have in AC3D to help in preparing models for 3D printing:

• Better extrude by normal. I roughed some math in pseudo code on this thread that keeps the new surface parallel to the old surface so the extrusion distance is more exact.
  
• Water tight test. I believe ensuring every edge is shared by exactly two edges is a simple test of water tightness. Perhaps the plug-in could change leaky surfaces to a specified material. A brief look through the SDK makes me think this is already 95% done in AC3D.
  
• Consistent normals. Once we've achieved every edge being shared by exactly (one or) two vertexes, I think if we test the edges to ensure one goes from V0->V1 and the other goes from V1->V0 we can know the normals are consistent.
  

I am hoping to gain some free time in the near future to work on these things. If someone would like to step-up to mentor my on the internals of AC3D, that would be great.

There are also some things I don't have an idea how to solve:

• Self-intersection test. Testing to make sure no surfaces intersect each other.
  
• Wall thickness test. The 3D print service I've been using has minimum required wall thicknesses.
  
• Object volume. The 3D print service I've been using also charges by the cubic centimeter, so it would be nice to figure out how much a model would cost before I upload it.

[jentron]

Is it possible to switch selection modes from C++? I don't see a prototype in the SDK header but see a few candidate functions in the binary:

• set_new_select_mode_ui
• set_new_select_mode
• add_undoable_change_select_mode
• set_select_mode_ui %s
• set_select_mode

I assume I should do something like:
add_undoable_change_select_mode("My Plugin thing");
set_select_mode(SELECT_SURFACE);

But I don't know what the prototype should look like or which of the 4 sets is the 'best' to use?

Thanks,

Ron

(Extrude by normal switches to surface mode and leaves the new surfaces selected. I would like to emulate that. Also, in the watertightness plug-in I would like to switch to surface mode and leave any "bad" surfaces selected.)

[Andy]

You should probably use this one:

Prototype void add_undoable_change_select_mode(int newmode, char *undotext) // remembers selection and changes to new mode

Originally Posted by jentron

Is it possible to switch selection modes from C++? I don't see a prototype in the SDK header but see a few candidate functions in the binary:

• set_new_select_mode_ui
• set_new_select_mode
• add_undoable_change_select_mode
• set_select_mode_ui %s
• set_select_mode

I assume I should do something like:
add_undoable_change_select_mode("My Plugin thing");
set_select_mode(SELECT_SURFACE);

But I don't know what the prototype should look like or which of the 4 sets is the 'best' to use?

Thanks,

Ron

(Extrude by normal switches to surface mode and leaves the new surfaces selected. I would like to emulate that. Also, in the watertightness plug-in I would like to switch to surface mode and leave any "bad" surfaces selected.)

[Edymnion]

Having a plugin that could essentially smoke test a mesh to see if it were ready for 3D printing would definitely be something I'd be interested in.

Something that could determine if a mesh was water tight and then automatically ensure that all of the surfaces were facing out correctly would be very useful indeed.

[jentron]

Edymnion,

I have a plug-in now that selects leaky surfaces. When I ran it on the Tardis model you uploaded it pointed out several leaky edges:

The dome light had a few "extra surfaces." I know Shapeways.com doesn't like those.
The right side vertical panels had a vertex that didn't connect to the horizontal panel.
The handles didn't have surfaces on their rears.

If you'd like a copy of the source code, let me know.

Ron

[Andy]

Sounds great - Yes please!

[jentron]

https://gitorious.org/ac3d-plugins/watertight

Includes watertight.cpp and a Linux makefile. With thanks to Dennis Hawthorne for selcon.

[Edymnion]

Excellent, gratci!

[jentron]

Andy wrote:
"AC3D 7.2 also includes Ron Jensen's plugin for checking the integrity of an object prior to 3D printing."

I guess I'm (in)famous now.

[Edymnion]

Been using this one a lot with my latest project. If for nothing else, its awesome at finding places where I extruded a surface and it left behind a wall inside the model that I didn't see (which proceeds to wreak havoc when subdividing).