# Dealing with complex curvature

**URL:** <https://discourse.shapr3d.com/t/dealing-with-complex-curvature/17536>\
**Category:** Modeling Questions\
**Created:** [February 19, 2022, 8:52pm UTC](https://discourse.shapr3d.com/t/dealing-with-complex-curvature/17536 "2022-02-19T20:52:12Z")\
**Posts on this page:** 1\
**Showing post:** 9

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**Author:** ![PEC](https://avatars.discourse-cdn.com/v4/letter/p/67e7ee/32.png) [@PEC](https://discourse.shapr3d.com/u/PEC)\
**Post date:** [February 20, 2022, 3:28pm UTC](https://discourse.shapr3d.com/t/dealing-with-complex-curvature/17536/9 "2022-02-20T15:28:54Z")

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Hi  
Here how I proceeded, the key point is that elements that are shared by two orthogonal planes **must** be perfectly at the same position. Almost the same is not good enough. The loft tool has no tolerance at all on this aspect.  
1- create a spline curve **in fit mode**. This is important because we want the curve to pass exactly at the control points. Ensure the tangent on the top is horizontal if you want a smooth surface. **Lock the curve**. This is important because we don’t want it to move later on.  
2- create the vertical and horizontal lines to close the shape and **lock them**.  
3 and 4 : mirror the spline regarding the vertical line.  
5 : leave the sketching view and click on the top point (intersection of the 2 splines and the vertical line) : the original spline + mirrored one + vertical line must highlight, which proves they are connected.  
6 : select the splines and the vertical axis, and make a 90° rotation around axis with copy  
7-8-9 : **this is the key point** : the two perpendicular lines are not always connected : click on the top point of the rotated splines (7), move this point up (8) and then back to the original position (9).  
Now, the 4 splines highlight and there top point is the same.  
10- **lock** this top point so it won’t move anymore.  
And now go the the newly created sketch and edit the shape of the splines.

More generally, I do the 7-8-9 check at every point that is common to several sketches planes, because you don’t know for sure to which the point belongs to.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/2/202fd12df7b5d0abc8ecbc839105a33fc61e9751.jpeg)

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