Why is spline jagged and not smooth?

tim_mckay · June 2019

Long story short, I just opened onshape and I am building a fully parametric wing. I've done this on many CAD programs. I use 9 specific segments all parametric driven by the chord length. I then make a spline for the top and bottom surface connecting each point. Then I used a bridge curve or whatever I have to to get a proper nose shape.

When doing this in Onshape I am getting a jagged and not smooth spline. The strange thing is if I grab the tangent handle at the end of a spline and hold down the left mouse button the spline will smooth itself out. I thought this might be a visual thing where it is only when zoomed it, but I extruded the surface as a quick test and it is a poor surface. I'm I doing something wrong?

Also is there any tool to visually inspect the surface quality of a swept sheet?

Attached is a picture where you can see in Fig 1 the airfoil profile build out, then in Fig 2 you can see the jagged splines, then in Fig 3 you can see while holding down the handle point the spline smooths out...but once you release that it snaps back to a jagged spline.

Thanks....

Image: https://us.v-cdn.net/5022071/uploads/editor/0s/hy76qcak4ewn.jpg

NeilCooke · June 2019

The mathematical shape of the curve is correct. See here for similar issue https://forum.onshape.com/discussion/11817/arc-circle-curve-segmentation-in-sketches/p1

tim_mckay · June 2019

@NeilCooke I read that thread...I was able to improve the surface bodies by right clicking them individually and editing their appearance to 'very fine' tessellation, thanks...

1) Is there a way to make the entire part 'very fine' tessellation from the start so you do not have to right click each solid or surface and edit the appearance?

2) This solution does not fix the poor tessellation of the sketch, is this something you all are working on? A lot of times the spline isn't touching the attachment points even when not zoomed it(see attachement). I don't have a problem with some tessellation, but this seems a bit much when not zoomed in much.

Thanks in advance.