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Surface loft curvature tangency failing with guides
amCAD
Member Posts: 12 ✭✭
Hello. I was trying to follow the process shown in this tutorial for surface modelling.
The sketches in the video tutorial are fully defined. Mine are not, because I was merely testing the process.
https://youtu.be/a0kZGWsT6sY?t=14m28s
At the point of creating a surface loft for the half of the chair which will later have to be mirrored
- I set the end profile condition to Normal, the loft preview regularly appears
- I select guidelines (appositely created as splines with tangency to the X direction) and the loft fails
I can only use those guidelines if I don't set any condition to the loft's End profile, but then of course the part will not have continuous curvature after it gets mirrored.
One thing I noticed, my model has a similar issue to the one he fixes at 15:03 and 15:16, but I wouldn't know if that's the thing which is causing the issue, and even if it was, I don't see the option to anchor the point to a sketch when I create the "3D fit spline 1" in my model.
My test model... https://cad.onshape.com/documents/49c786d107c712bedee6d65d/w/8a1a53217abf72a816256e60/e/ae08deb2a645555475cac485
Any guesses? Thanks
The sketches in the video tutorial are fully defined. Mine are not, because I was merely testing the process.
https://youtu.be/a0kZGWsT6sY?t=14m28sAt the point of creating a surface loft for the half of the chair which will later have to be mirrored
- I set the end profile condition to Normal, the loft preview regularly appears
- I select guidelines (appositely created as splines with tangency to the X direction) and the loft fails
I can only use those guidelines if I don't set any condition to the loft's End profile, but then of course the part will not have continuous curvature after it gets mirrored.
One thing I noticed, my model has a similar issue to the one he fixes at 15:03 and 15:16, but I wouldn't know if that's the thing which is causing the issue, and even if it was, I don't see the option to anchor the point to a sketch when I create the "3D fit spline 1" in my model.
My test model... https://cad.onshape.com/documents/49c786d107c712bedee6d65d/w/8a1a53217abf72a816256e60/e/ae08deb2a645555475cac485
Any guesses? Thanks
0
Comments
Still having troubles though. I didn't mention in the earlier post, but I tried that too (Normal to profile condition with "0" magnitude).
It looks to me that the "0" value (any other value will make the loft feature fail) nullifies the "normal to sketch" property, since I still see the chair being split right there at the midplane as if the "Normal to sketch" option was not enabled ("curvature visualization" mode or "shaded without edges" makes it easier to notice).
My question is if it's currently possible to create the object as seen in the video tutorial, without a "crest" alongside the midplane after the mirror feature. The only way I was able to have the smooth surface after the mirroring was without implementing the two guide-curves.
And if it's not currently possibile that's great too. I can see the Onshape team paying a lot of attention updating, improving and adding surface modelling tools and I don't know if this this case might eventually help sorting out possible issues of coexistence of loft profile end-conditions with guide-curves.
Thank you again.
Technically Fill feature can handle these cases better (you can indeed select a sketch edge and ask the surface to be curvature continuous, which you can't do with Loft). However in this case I'm assuming due to the tight tip (upper back of the chair), the curvature constraint fails. I will try a bit more, and maybe someone else in the community can come up with a solution
https://cad.onshape.com/documents/cf944d0d25d8940e144289e1/w/9cec00853bedd83122684aa9/e/88b6715dde49685e7da76967
https://cad.onshape.com/documents/cf944d0d25d8940e144289e1/w/9cec00853bedd83122684aa9/e/3be58ac18405ae0b0b46e352
which does not require curvature continuity to get better curvature lines.
projektowanieproduktow.wordpress.com
projektowanieproduktow.wordpress.com
I actually had an intuition about using something like a surface normal to the midplane but I couldn't practically make it work and soon discarded the idea. Will use this procedure from now on whenever needed.
Thank you so much for your help, elif and michał_1.
Much appreciated.