backpack design challenge

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looo
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backpack design challenge

Postby looo » Sat Aug 11, 2018 10:43 am

Dear FreeCAD-community :)

I want to make a little design challenge. The goal is to create a backpack for carrying an ultralight paraglider (~2kg) + equipment. I would like to involve the community in the design procedure, as the community-knowledge is one of the main strengths of FreeCAD. Also I have to admit that I do not have much knowledge about curves and surface workbenches (which I think will play a big part for this project to succeed)

I already did one prototype, which mainly was about testing the mesh-unwrapping features [1]. This prototype is for sure not very well designed (using part, and part-design, draft)[2]. I guess the curves and surface workbench will give much more advanced possibilities.

As we use a 3d modeler for this task, I would like to integrate design and functionality as much as possible. For example normally the straps of the backpack are simple attached and more like a 2d part. My idea was to make the connection between straps and pack via a 3d design. Also other ideas how to integrate design and functionality as much as possible are welcome.

For sure your ideas will be honored. If we manage to get this project done, we will contribute back via donations to FreeCAD. Also I think it's a way to improve/test workbenches and tools.

So keep the ideas coming :D

[1] https://forum.freecadweb.org/viewtopic. ... 50#p217652
[2] https://forum.freecadweb.org/viewtopic. ... 90#p217386

edit.: one limitation for the project is that everything has to work with python3, so maybe this is also a nice task to get workbenches, tools ready for python3...
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dbecad
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Re: backpack design challenge

Postby dbecad » Sun Aug 12, 2018 1:26 am

One of the coolest design I saw recently is this armadillo shape shell backpack:
https://mypangolin.com/collections/renegade
Maybe easier to design than some completely soft fabric surface? Each of the segments are flat and stiff and bent in 1 direction, there is an inside liner to fill the gap between the segments and regulate their spacing.
Cheers
-dbe
looo
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Re: backpack design challenge

Postby looo » Sun Aug 12, 2018 5:23 pm

Very interesting design, but not what we are looking for. The backpack should be made from thin clothes to be as lightweight as possible. It should have a bit of volume (30-40 litre) to store the eqippement. No other constraints so far
..
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looo
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Re: backpack design challenge

Postby looo » Tue Aug 14, 2018 1:17 pm

Today I made some progress with the surface-creation. I guess what I really need is an interactive tool to manipulate the poles of a bspline surface...

So the workflow will be like this:
- create a 2d-face from sketcher-bsplines
- convert the face to nurbs
- get poles, weights, knots and compute the influence matrix (for given uv-points)
- drag poles and compute a quadmesh (interactive design)
- once result is satisfying get back a shape

no idea if this can be done fully parametric.

This is the direction I want to go:
first_design.png
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looo
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Re: backpack design challenge

Postby looo » Wed Aug 15, 2018 9:09 am

adding the straps should work with one bspline surface.
version1.png
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triplus
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Re: backpack design challenge

Postby triplus » Wed Aug 15, 2018 3:33 pm

Nice project.
looo wrote:
Tue Aug 14, 2018 1:17 pm
I guess what I really need is an interactive tool to manipulate the poles of a bspline surface...
That too. But as for the next step. There are around 4 developers tackling surfaces directly and as a personal point of interest. And around 2 more having the knowledge when it comes to splines and have done some work in this area in the past. Anyway a lot of experimenting have been going on in the past. Things likely have matured for all this to be gathered under some common goal. And to achieve some basic but more streamlined surface related tools for FreeCAD in one or two development cycles. Somebody would i guess need to outline the basic goals and invite others to collaborate.

Anyway interested to see how the backpack challenge will evolve therefore keep us updated. For the things that currently don't work or can't be achieved. It makes sense to mention that too. On how it i guess should work but it doesn't ATM.
looo
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Re: backpack design challenge

Postby looo » Thu Aug 16, 2018 11:41 am

triplus wrote:Nice project.
It's something I wanted to do for a long time. If the project succeeds I think we can also have a FreeCAD-version with logo and laptop pocket :D But some prototypes have to be made first.
triplus wrote:That too. But as for the next step. There are around 4 developers tackling surfaces directly and as a personal point of interest. And around 2 more having the knowledge when it comes to splines and have done some work in this area in the past. Anyway a lot of experimenting have been going on in the past. Things likely have matured for all this to be gathered under some common goal.
Yes I absolutely agree. To make tools usable efforts have to be merged and compromises have to be found. But the step from getting a workflow useable for my own tasks to getting something ready to be as generic as possible and acceptable from the average user is quite big... Also there is another problem: Interactive Spline-design is not parametric. At least I don't know how you can do this in an parametric way. (eg.: adding additional poles) So I don't know if this work-flow will satisfy the average freecad-user used to parametric objects...
Another problem I see with the interaction nodes them self: If we add them to FreeCAD master, we will somehow depend on pivy... As we have seen support for coin and pivy won't last for ever. So I don't know how much sense it makes to add additional stuff which will be very hard to port to something like vulkan-osg. I guess porting the sketcher interaction-nodes will be already difficult enough, so nobody want to do this... In my mind we should abandon the idea of ever switching from opengl to vulkan!!!
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freecad-heini-1
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Re: backpack design challenge

Postby freecad-heini-1 » Fri Aug 17, 2018 12:39 pm

looo wrote:
Tue Aug 14, 2018 1:17 pm
I guess what I really need is an interactive tool to manipulate the poles of a bspline surface...
+1
Like the Moi3D helmet.
phpBB [video]
looo
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Re: backpack design challenge

Postby looo » Sat Aug 18, 2018 4:57 am

freecad-heini-1 wrote: Like the Moi3D helmet.
I am not sure if curve-design alone will be enough. Currently I am manipulating the poles of the surfaces directly. But I guess with curves it's possible to create a more parametric workflow

This is how the current design is made:
The slow fps is coming from the capturing tool. But the computation is quite fast. The nurbs representation is computed in python, but the heavy part is done as a sparse-matrix (scipy) product, which is quite fast.
interaction.gif
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hammax
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Re: backpack design challenge

Postby hammax » Sat Aug 18, 2018 8:04 am

… some days ago I saw some longdistance-paragliders in TV with something like an inflatable trailingedge
in/on their bagpacks, I suppose to reduce leeward drag.

Backpack_h.PNG
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