To Project one curve
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 From:  jbshorty
286.8 
it does work as Michael described, but not in perspective (3D) view. You must be in an orthogonal view (front, left, right, back, etc...)...

jonah
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 From:  Frenchy Pilou (PILOU)
286.9 In reply to 286.8 

In fact that works even in 3d view as Michael said :)
Just makes as he said (after that you see on the image)
Select the "projected line" : Ctrl + C = Copy
Undo = kill the trim
Ctrl + V = repast the "projected line" on the surface
et voila :)

EDITED: 10 Jan 2007 by PILOU

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 From:  jbshorty
286.10 In reply to 286.9 

it does and it doesn't. there are a few trouble spots when using this technique in 3D view:

1) ability to trim is affected by the rotation of the curve. find a situation that trims a surface, then rotate the curve 90 degrees and try it again. Does it still work?

2) what axis are you intending to project along? I think Moi defaults to whatever seems most logical based on position of the objects. that's fine for most cases, but maybe not always.

3) If your object and your trim curve are centered around same location, which axis will it use?

4) How do you trim along Z-axis?

all of these issues are resolved by using an orthogonal view. It also helps to visualize exactly where the trim will be created...

jonah

EDIT - It seems this technique also has some strange reults created by "pulling" the curve towards the 0,0,0 origin when i trimmed along the Z axis, the resulting trim curve was pulled off the axis. So it seems there is no way to trim along the Z unless you first rotate an object and then trim along X or Y... Also i think maybe the results are affected by a curve being planar or non-planar...

EDITED: 10 Jan 2007 by JBSHORTY

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 From:  Michael Gibson
286.11 In reply to 286.10 
Re: trim projection.

When trimming curves to other curves, the view you use can make a difference if the curves don't intersect and need to be projected to intersect. The construction plane of the view will get used for that projection.

But trimming a surface or solid to a curve is not view dependent in MoI - you will get the same results for this no matter which viewport you use, which is a little different than Rhino.

The process works like this - the first thing that is checked is if the curve is actually already on top of the surface or solid - if it is then it will not be projected. I guess this might be good to change since it can inhibit the projection of a planar curve through to the other side of the object.

Anyway, the next test is if the curve is planar. If it is then it will be projected along its plane normal.

If it is not planar, then it will get sucked down on to the surface by finding the closest point on the surface for every point on the curve ("pullback" method in Rhino).

So the view used actually doesn't have any influence on curve-to-surface projection.

If you want explicit control over the projection direction, you can just extrude your curve along the desired direction and use the extrusion for the cutting object in the trim.

- Michael
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 From:  Frenchy Pilou (PILOU)
286.12 

Useful precisions
So the extrud + direction is the best friend of triming / Projection

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