Project to Brep doesn't work in R7

When I try and Project a curve to a Brep in R7 it misses off the part of the curve above the X-axis…

R5 >>

R7 >>

image (11.0 KB)

Has the Project component changed in R7?
Will I find this happening in many other components?

R6 behaves the same as R7, regardless of whether the curve is above, below or inside the brep. But it works as expected on the surface’s Bounding Box.

It’s different in R5

I need to project it on to the revolved surface.

Work fine, Rhino 7

Extruding the curve fails to intersect that surface!? (R6)

Solid Intersection fails as well. That surface is not a “Closed Brep”?


I think there’s something weird going on with your original surface:

bake -> duplicate edges

redrawing the surface with revolve around Z axis gives no problem: (54.1 KB) [edit: wrong file attached]


Something still looks weird to me… I can’t reproduce your result starting with plane intersection.
Why would a full ellipse need to be revolved ‘0 To 2*Pi’?
Seems like 180 degrees (‘0 To Pi’) should be enough?

P.S. OK, I got it to work by using YZ for intersection which yields one half ellipse curve, which can be rotated ‘2*Pi’ (360 degrees) to give a surface that works fine with Project and other tests. (14.8 KB)

Using XZ for plane intersection yielded two full ellipse curves. Rotating one of them 180 degrees (Pi) didn’t work.

Bottom line was that your “bad” Srf was likely created by rotating a full ellipse ‘0 To 2*Pi’?

This interruption to the forum while trying to edit this post DROVE ME MAD!!! until I finally noticed the message:

This site is in read only mode. Please continue to browse, but replying, likes, and other actions are disabled for now.


Thanks… I will look again properly tonight when Lockdown childcare is over!

It’s strange because it works in R5… maybe it is not the Project to Brep component but something to do with the revolve surface component but that just revolves an ellipse through 0 to pi.

Attached is the full gh def up to the project component and below shows that the curves I want to project lie within the Brep so should intersect (and indeed do work in R5) (41.3 KB)

Ah, it works if I split the ellipse and rotate 0 to 2*pi…


Strange why R7 doesn’t like it the other way though!

Who would? I tried to say the same thing yesterday. Can you explain this? (in code you just posted)

Using YZ gives half an ellipse. Using XZ gives two full ellipses. Why?

The original surface in the first post was created by rotating a full ellipse through 0 to pi radians not, as you asked, through 0 to 2*pi. You can see that in the def I posted above… the D Domain input for the RevSrf is 0 to pi

Thanks for the idea to use a half ellipse. I had misunderstood some of your reply about
intersecting the internalised surface but I see what you were doing now.

I have no idea why…

I guess the lesson here is do not use a closed curve, rotated 0 to pi for RevSrf.

I seem to have a vague memory of a discussion about this either here or on the old forum. Does it create a bad seam in the surface?

I had no way to know that from yesterday’s code so was speculating. I tried everything.

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