Curve Free-Form Sketch draw on Polygon Mesh alteration

While drawing a curve on a Mesh surface and going upwards, the curve is visible and goes OK, but when you reach a certain height on the screen, the drawing of the curve stops until you come back to the lower área of the screen (where the curve stopped), and at this point (height) the curve returns to normal drawing, and is suddenly connected to the last part of the curve that was originally visible, not obeying to the last path that was drawn.
Seems that something occurs, that in the lower part of the screen the command is well executed, but in the upper part or área of the screen, it ceases to work normally.

Hi Rafa- what command are you using? and can you post a file that shows the problem?



Hi Pascal.
I have a female body as an Open Mesh.
My intention is to draw three equal curves, closed, resembling three vertical ellipses.
The first in the leg, the second higher and to the rigth of the first one, and the third more to the rigth and higher than the second.
So I use the command Curve/Free-Form/Sketch on Polygon Mesh (closed)
Then I draw manually with the mouse the first vertical curve (kind of an ellipse) as the “First curve” layer (in black) and the whole curve is accepted as it was drawn. Until this point everything is OK.
But then I draw the next curve (“Second curve” layer in blue) as similar as possible to the first one (same vertical and horizontal dimensions) and the problem begins then when the curve reaches a certain heigth, and the drawing line disappears until I go down again for finishing and closing the ellipse. Here, when the curve is at the same height where it disappeared, it suddenly appears again and is automatically connected to the fisrt part that was drawn OK. As result of this problem, the curve is small and is cut in its height.
In the third attempt with the third ellipse (“Third curve” layer in green) again I try to draw an ellipse as similar as possible to the first one, but again it is cut at the same altitude (like an horizontal imaginary border).
So in a short description, the second and third ellipses cannot be drawn as they should be in their correct vertical dimension (like the first one) because they are cut in a kind of horizontal band where both curves disappear. Sketch curves on a body.3dm (2.6 MB)

Hi Pascal
As I supposed the versión I was working with, was automatically detected and established, I omitted to tell you I work with versión 5.0.2 for Mac for evaluation.
In the posts I have been working on I have just seen a flag of “Rhino for Windows” so it is not OK. The images and file I sent you is from my Mac.
So I am sorry about my ommission and now the problem I am having can be clearer to you.

Tank you,

(changed to Rhino for Mac category)

Hello again Pascal.

I have not received any answer to the problem I am having.
What can I do?


Hi Rafa,

Try turning on Vertex Osnaps while you draw the curves. This works fine here to draw three loops on the mesh. Another option would be to disable Osnaps and draw the curves in an orthographic view. Then use the Project command to apply them to the mesh.

Hi Brian.

With your clue of using the Vertex Snap, using the “On mesh” snap resolved the problem.
Now I can draw any curve on the Mesh I need.

Thank you very much,