Can't project a group of curves onto a polysurface. Any idea?

I used the project command in the past and it worked well, but this time it’s not working as I expected.
I constructed a set of panels that are slightly inclined inward (as would pyramid walls). I then constructed a set of closed curves that represent the holes I need to extrude on each panel so that it creates an extruded structure (similar to punching holes in a metal sheet to obtain a perforated surface).
I thought I could “map” those curves onto the surface of each panel so that I matches the shape and orientation of the panel, but I can’t get it to work.
So I’m definitely doing something wrong here… Any advice would be welcome! Thank you.

Hi David - Better post the file… otherwise we’ll just be making stuff up. My guess, in the meantime, is that you probably want to set a CPlane (CPlane>Object) to the surfaces and draw your curves in place. RemapToCPlane could also come in handy. Keep in mind that Project uses the current CPlane normal as the projection direction, so any input curves or target surfaces that are not parallel to that plane will result in distorted projections.


1 Like

Hi Pascal,

Thank you for your time and recommendation.
Yes, I thought I should post at least a picture of the current problem. The full project is under NDA, though. I’ll follow your recommendations, and if I keep messing up, I’ll post some files.

This is where fear of messing up comes in. I still don’t have a good commend of setting C-plane to any targeted surfaces.
I thought I could use the commend “OrientOnSurface” but it very erratic… I also thought that Rhino would have a simple commend as such as “Map onto surface”. One could take a group of drawings, map them on the target surface (either distorted or rigid) and then follow up with for example extrusion or embossing?


As Pascal says, we start making things up when we don’t see what’s going on but I was wondering in which direction your extrusion will go. Will it be perpendicular to the sloping surface or parallel to the XY plane? I would assume the latter (this is where I start making up things). If so, you are better off just extruding those and then trimming surfaces.

“Project” projects perpendicular to the current C-Plane. Remember that in Perspective view the default current C-Plane is the in the plane of the global X-Y axis. Project does not depend on the camera location.

Pull is another useful command. It pulls an object towards a target surface. If the target surface is a plane then it is equivalent to setting the C-Plane to the target surface plane and using Project. If the target surface is curved it pulls the object onto the surface based on the local surface normal. “Pull” may be equivalent to the your desired “Map onto surface”.

Also consider creating a simple example of the problem you are having to post here.

The extrusions have to be parallel to the panel (that is to the sloping surface).
In the same range of idea, I aligned my extrusion pattern the best I could to the slop and tried to extrude from there but the result is unreliable and not precise at all.

Hi David,
Thank you for your contribution.
Yes, you, Pascal and Wim are right about the C-Plane issue. After a few hours trying several methods found on the McNeel tutorials, I started to realize that the C-Plane might be the key factor. So, after I read your comments I started to train myself with some exercises on shifting C-Plane from a surface to another and so on. It starts to make a lot of sense. It is like re-orienting one’s paper sheet when sketching on free paper.
I’ll try the “Pull” commend today and will let you know how it goes (including some demo of the situation).
Thank you!