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# Curve from projections

savi_garcia
Member Posts:

**6**✭Let's create two vectors (using bridge curves) `V1`

and `V2`

. There aren't parallel or anti-parallel.

Let's then create two planes (via mid-plane, or line-angle) `P1`

and `P2`

. Then, we draw two curves `C1`

and `C2`

upon these planes.

Is there a way to compute the final 3D curve `Cf`

, such that these two curves `C1`

and `C2`

will be the projections of` Cf`

upon `P1`

and `P2`

?

For reference, we can do this on freecad using Curve Workbench→ Mix Curves. Thank you

0

## Answers

5,574Can you create a document manually to show what you are trying to achieve. Initial gut feel is no, not in a single step without FeatureScript.

6✭Ok, to clarify: If i create a document in onshape mimicking what I want to do, would that suffice?

As I dont know how to do what I want to do on OnShape, actually doing it is out of question

170It's a pretty abstract description but I've made something - perhaps you can tell us if it is correct or not…

The orange curve (Cf) is the 3d projection of C1 and C2 which are on P1 and P2 respectively.

https://cad.onshape.com/documents/ebc0f2bd740d39f521ad64f2/w/c7a3e902abc311796c4b0024/e/287740c3ba6adbf6e00179d8

6✭YES that is where I am trying to go- In the first and second examination it looks perfect.However I'd also like to know, if there's a tolerance/error in the result that is inherent to the calculation that onShape does.

170The projection is very accurate, within the very tight tolerance of the modeling kernel. The curve resulting from the projection of 2 sketches is calculated by the intersection between extruded surfaces. This intersection curve will (likely) be a multispan deg3 curve. (For trivial cases of projecting 2 line segments, the projection will also be a line/deg1 curve). You can experiment by reprojecting the intersection back onto a plane and see no loss of original fidelity.

6✭Thank you.

Now, and actual application:

https://cad.onshape.com/documents/8554fe39d930f846602f9194/w/ccaadf1311aaa66bad50dcba/e/d959ef0d904f87e3f25b9f08?renderMode=0&uiState=66dd5a32dcc2976b5f7ee031

Consider the planes: Plane_TEST_00 and Plane_TEST_01, and the curves CURVE_00 and CURVE_01.

I select

projected curve; and then select "two curves" - and then choose the curves CURVE_00 and CURVE_01 as the two sketches. This fails the generation.If i modify the curves to be more "rounded", i.e, make the turns softer, it

willwork out.That leads me to the next question:What limitations should I take into mind for applying this procedure? Thank you.