Hello,

I used openscad to design my new thing.
(To fix ideas, imagine 16 alu profile, ~30 small laser cuts, ~150
screws-nuts-rivet, ~10 parts from shelf)

I'm currently in the process of writing an assembly manual for the end user,
who will assemble everything.

I'd like to get something that looks like an ikea manual.
Kind of simplified wireframe perspective view, black&white optimized for
printing.

And I'd like to be able to modify my model and simply regenerate all the
assembly views as automated as possible.

I know that in openscad I can programmatically set a view (camera position &
direction, angle, etc...)

How would you do?
Play with openscad wireframe view, change the colors to just black and
white, and export bitmap?
Rotate the object, and make a projection, to export dxf?
Or export a 3D model, STL, or CSG, and process with an external tool, and
which one?

any idea, advice, experience feedback will be much appreciated, Pierre

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You are tackling a problem I had many times, but never found enough reason to
go deeper into it and implement a solution. I think many people are
confronted with it and would appreciate to have some build-in function at
best, or at least a viable solution for this.

Let me sketch my approach, which is - no wonder - quite similar to the
algorithm I proposed to Jon in  the  flattening curved surfaces
http://forum.openscad.org/flattening-curved-surfaces-tp19727p19736.html
thread.
Jon wanted to unroll dominant surfaces of 3D objects (by the way, Jon, how
is your progress?) on 2D. For this he had to separate the model into a set
of surfaces. Using the assumption the surfaces are unrollable, it is enough
to test the scalar product of the normals of adjoint triags against a
threshold.

The same approach can be used to find the dominant "borders" of a surface.
In this case the unrollability assumption can be weakend into a "almost
unrollable" criterium, which (I hope: to Ronaldos relief) is exactly the
semantics of the threshold test. Let's draw "almost unrollable surfaces", by
skipping less important lines and staying in 3D.

So a "cheap" recipe could be: find all common edges of all adjoint triag
pairs, for which the threshold test fails and draw them on top of the model
similar to the visualisation in my  unrolling sufaces demo
http://forum.openscad.org/flattening-curved-surfaces-tp19727p19807.html  .

While this little helper is a someliner e.g. in Matlab, it is (again) beyond
the scope of OpenSCAD language as long as no import function for STL data is
available. Having this import function would serve many more requests - from
boundingboxes, calculating distortions, calculating testless unions and many
more.

So my question to the dev team would be: Is it planned, or are there any
objections I might have missed?

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@tp3 : Thanks! Although I didn't know blender and it looks like an airliner
cockpit for beginner like me, I managed to find the three options to get
there :
http://forum.openscad.org/file/n20111/4.png

To be honest, the result is better than expected. :-)

Now I just have to found a way to render let's say 30 different views
without redoing everything 30 times.
But it's not anymore an openscad issue....

@Parkinbot, I must admit your approach is not very clear to me, but anyway,
thanks.

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@Parkinbot

I haven't understood your approach either. Maybe you are trying to find the
silhouette edges of the model seeing from a point of view.

Regarding "import function for STL data": this is a reiterate
question/feature request here. I myself asked in a recent thread why
bounding box functions (which are computed by resize(), for instance) is not
available in code level. Torsten answer that: " internally the geometry will
be known, there's currently no
means to communicate this information to the back to the script." So, I
understand it as a language limitation: there is no way a function can
receive a model as input in the current language. It will be easy in
OpenSCAD2 though.

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Of course (and it's a note to myself in the same time, good idea) :

after deleting default cube, importing your stl, set your view, ctlr+alt+0
to set the camera view.

In World properties, change "Horizon color" to white
In Render tab
resolution 1920x100 100%
check "Freestyle"
In Render layers tab :
under 'layer', uncheck solid
under 'freestyle line style, thickness at 1.5

Render...

That should be enough.

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