Evaluating the right tool to start working on RE engineering task as a new service for an existing company.
No experience on CAD, the first customer demand are eyewear and nautical propeller.
The parent company does have CATIA seats, but IMHO this is a steep start on the task.
Searching for easier yest complete solutions I was looking at Rhino and SpaceClaim.
Some doubts:
- does Rhino have specific tools for RE, or I did need to add T-Splines, RhinoResurf or Mesh2Surface.
- how steep is the learning curve vs CATIA.
- does Rhino on RE create only surfaces or also solids
@davide445,
for doing accurate freeforms with continuity between (trimmed) surfaces check out RhinoReverse. Mesh2Surface is more directed to mechanical reverse engineering.
Rhino is a surface modeler, but a closed polysurface counts as a solid. The learning curve is relatively flat, however RE is a job on itself and requires quite some experience. Many basic tools for remodeling are available in core Rhino.
c.
Thanks.
Free-form surfaces are the only form of RE in Rhino, or will be possible i.e. to blend sections of the mesh as borders?
Not sure if i understand this. If you mean blending naked mesh edges with curves, this is possible. Blending surfaces is possible too, if you have surface edges to blend from. Maybe you could show an example file of a mesh you plan to reverse engineer with Rhino / RhinoPlugins ?
c.
Attached a (very bad) scan of part of the eyewear sidepiece.
With blending I did mean cutting the part using parallel planes and reconstruct the profile using the cuts profile, as I’ve done as a test in SpaceClaim.
An alternative method of RE vs surfaces, but I did find it useful for more regular mechanic shapes (i.e. the propeller we will RE as next activity).
@davide445,
the slicing & cutting can be done without additional plugins in Rhino. You might try out the demo version using commands like _Section, _Contour, _Project (to project lines and curves on the mesh) and _MeshSplit to split the mesh with planes. I think that creation of mechanical shapes also does not require any additional tools.
c.
As clement suggests, use Section or Contour to create curves from the mesh. I have done this when modeling boat hulls using dense surface meshes from photogrammetry.
Rhino has several methods to create surfaces from curves. The user needs to know how to use Rhino to model the part. It is not a simple “push button” operation.
If the plain eyeframe temple is typical of the “reverse engineering” you anticipate frequenting, it would made more sense to just skip the 3D scan altogether and model it using careful caliper measurements:
http://b9c.com/forum/viewtopic.php?f=22&t=371
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Ok will check this feature, also to understand the Rhino learning path compared with SpaceClaim.
Need to do full eyewear RE, this part is just a test. Next request nautical propeller.
Tried the Section tool, really easy to use.
How is possible to do the next step, I suppose the JoinCurves?
Really new to Rhino I’m just trying to understand the easier way to achieve our goals.
@davide445,
after sectioning you usually start to cleanup the resulting polylines into usable curves for your construction. Either by rebuilding with a lower pointcount or in case of curved forms using a higher degree than 1. Then use the cleanup curves for your modeling.
Note that proper alignment of your mesh before doing all this is recommended.
c.
@clement
any hint about the commands needed to clean up the lines?
Experimenting the workflow with many programs I’m overwhelmed with manuals and commands, the right hint can save me hours of trial and error.
@davide445,
for eg. rectangular sections made of a dense polyline, you might use _Split at the corners, using the _Point option on each corner, then use _Rebuild with degree = 1 and point count = 2.
To rebuild a curved Polyline e.g. into a real circle, _ExtractPt followed by _Circle _FitPoints gives good rational circles.
To rebuild a curved polyline into a smooth curve, you might just _Rebuild but with degree = 3 or more and check how accurate it gets if you change the point count. Then before doing the actual modeling, align all curve geometry eg. by projecting it into planes using commands like _ProjectToCPlane or _SetPt.
btw. for mesh pre-alignment i often do this ugly workaround to fit a plane surface to a mesh:
- smear a random zigzag curve an a planar area of the mesh using
_PolylineOnMesh
- use
_ExtractPt followed by _PlaneThroughPt
- finally orient the resulting plane and the mesh to the grid using
_Orient or _Orient3Pt
In general, if you start with Rhino and are doing reverse engineering work the first time, try to work with layers and colors to differentiate all jaggy polylines from smooth curves & clean lines. Only these should be used for the modeling. I´d also suggest to skip other programs than core Rhino and just start with the basic commands it offers. 
c.
To go from a polyline line with many points, created by sectioning a mesh, to a smooth degree 3 curve I usually Rebuild, RebuildCrvNonUniform and/or FitCrv.
I think will give up with Rhino, did find his UX really '90 style with all the command line and stateless design, need ages only to understand how to combine single tasks to perform simple operations.
This obviously IMHO and with the greatest respect of the real professional expert I did find in this forum.
Thanks for your help.
