Projecting body/sketch to a mesh or brep

[Anonymous]

Hello everyone,

Please forgive my naiveté, as I'm still learning the ropes of Fusion 360!

My goal of this design is to create a "head-post" which has a "X" base that curves perfectly along the surface of an imported-from-stl skull file, as seen in (1).

The skull is imported as a mesh, and as per some of the advice that I've seen online, I have reduced it and converted it to a Brep in order to work with it more easily.

Ive had 2 approaches to achieve my goal:

1) Create a body of the "X" base, and somehow project the face of the body, or the body itself (if that is possible?), along the surface of the skull to achieve that desired curve, as seen in (2). From here, to then proceed to build the actual "post" component and modify it to look like (1). 

2) Create 2 sculpted planes that intersect the surface of the skull in the desired manner, then do an intersection curve to create a line where the planes intersect the top surface of the skull, along the surface, to then sweep a rectangle across the line which should leave me with the curved "X" base, as seen in (3).

In both approaches I haven't been able to interact with the surface of the skull (Brep) easily. Im lost as to which workspace I should work within, as well as what tools I should use to achieve this general goal, with either approach. Any information that points me in the right direction would be tremendously appreciated. 

Please let me know if I can provide anymore information.

Thank you very much.

Paul

[davebYYPCU · Accepted solution]

The Projected curve method is closer to the right track.

It appears that the example has a top view profile, that is not a straight strip.

How much tolerance to the actual shape are you requiring.  

Design dependant - one leg at a time,

construct two planes and two Intersect curves, strip width apart,

for the two vertical faces, smooth the outcome with a spline.  Offsetting the Splines by the thickness of the material, gives you 4 Splines, Join the top to bottom end points on each sketch.  

Loft the left to right side profiles.  Repeat for other strap, combine and decorate to suit.

Might help......

[TrippyLighting · Accepted solution]

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@Anonymous wrote:

The skull is imported as a mesh, and as per some of the advice that I've seen online, I have reduced it and converted it to a Brep in order to work with it more easily. 

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Can you post the un-reduced .stl ?

As you've experienced converting a .stl into a BRep goes along with a substantial loss of detail. And of course the resulting BRep is faceted, and unless that is actually desired, is ugly as sin.

Does it have to be that particular skull or would another Skull also serve the purpose ?

Yep, I have a much better workflow in mind creating a much superior result!

It would also be a mesh, but as opposed to that horrendous triangulated .stl garbage it would be a pristine quad-mesh that can be turned easily into a buttery smooth T-Spline.

[Anonymous]

The design must be based on the geometry of this specific skull!

Ive attached the .STL file of the top surface.

Id be very appreciative if you could describe/screen cast your suggested workflow!

[Anonymous]

Thank you so much for your guidance!

With my lack of experience, I am able to follow your workflow, however when it comes down to implementation im a little lost - may I ask you to screen cast, should you have the time?

It seems that designing the legs isn't as much of a problem as is being able to interact with the surface of the skull, which is a Brep currently (converted from reduced mesh). While I have created my planes, I cannot seem to do an intersect curve as the surface of the skull is either un-selectable, or only one of the facets seems to get selected which throws things off. 

Closest design to the actual shape is preferable - no specific tolerance threshold. At this point, ill take what I can get!

Apologies if anything is unclear!

Ive attached the top surface .STL file!

[TrippyLighting · Accepted solution]

Is this the original .stl or the reduced version ?

This has a few artifacts I'd expect from a low quality scan. Holes, spurious vertices and triangles ...

Also, this only is is only about as big as my thumb. Is that the size you are looking for ?

[Anonymous]

This is the reduced .STL - I was unable to send in the original as it was far too large. 

Also, the dimensions are correct! It should be a little larger than a thumb.

The artifacts/holes shouldn't pose too much of a problem as long as the general shape of the skull's surface, primarily along the path of the "X" base, is captured. The original scan was not of the best quality, also!

[TrippyLighting · Accepted solution]

OK. Here is the skull, re-topologized in Blender and turned into a T-Spline in Fusion 360. I'd been waiting for a good not too difficult project to demonstrate this technique. It's very powerful and can be used effectively on more complex organic shapes.

I used this technique to get to a clean quad mesh:

[davebYYPCU · Accepted solution]

Lots of weird stuff today, this will be 3rd time to post the same answer, will leave the file off, see if that helps.

Send the file next one.

[davebYYPCU]

Nope can't get the file posted, back later in the day, can't do it now....

[Anonymous]

Thank you so much for your time !

[TrippyLighting]

If you can accept @davebYYPCU and my replies as the solution we can close this thread out.

[Anonymous]

Forgive me for returning to this thread!

Ive tried to repeat this process for a few different shapes of skulls since, and I haven't quite been able to produce such a quality re-topologized mesh as you have - not to mention converting it to a Tspline with only 4 faces.

Is it that you used only 4 planes in Blender (using the techniques shown in the video), or was this done in fusion?

I find that I have to use many planes to even generate an accurate shape of the surface of the skull, and even then it is not quite smooth.

Do you think that you could ever record a quick tutorial of how you achieved this? Its absolutely wonderful and I feel like it would be such a great contribution to the community - especially for beginners as I (0 prior experience in Blender).

Thank you so much for your time!

[TrippyLighting · Accepted solution]

Did you ever look at the T-Spline in the file I posted above ?

Here is a screenshot of it. Not sure how many T-Spline faces are in there but more than 4 😉

The 4 faces you are seeing are the NURBS surfaces that are created when the T-Spline is converted.

I would probably not use this approach anymore and use RetopoFlow 2. Ive retested it and it works very fast for this sort of stuff.

[TrippyLighting]

I also recently created a tutorial using a somewhat more automated approach that might be interesting for you to watch.