Hi Guy, and re: booleans - like Pilou if you have a hole in your object making it an open surface rather than a closed volume, then the booleans will behave differently, you are trying to work in this case with a now open surface since you basically "un-solidified" it when you did a trim on it initially instead of a boolean.

See here for some more information on boolean behavior with open surfaces:
http://moi3d.com/forum/index.php?webtag=MOI&msg=5195.14

If you want to use the booleans you usually need your base object to be a solid, and then they will work like you were expecting.

So your initial steps for creating this object would go like this - start with your base solid like so:



Then go to the 2D front view and draw in your curve cutting shape like this:



This looks like this in the 3D view now - it does not matter at what depth level the ellipse happens to be at:



Now, you do NOT need to do any more preparation work - if you're doing stuff like projecting curves on to surfaces and doing trims, that's all a bunch of extra work that you can just skip, instead let the booleans do all that work for you!

To get the final result, just select your solid here, and run Construct > Boolean > Diff, select the 2D ellipse curve as the cutting object and you will then get this result right away:



Check out the attached 3DM file for these objects - it's all set to boolean just run boolean difference and use the ellipse as the cutting object and you're done!

By the way these methods of doing booleans to cut solids with 2D curves is covered in the introductory video tutorials, if you have not watched them before it's probably a good idea to go over those, they will help get you going easier:
http://moi3d.com/2.0/docs/tutorials.htm

Basically if you just want to do simple "drill a hole with a 2D profile", and you have a solid as your base object, just draw in your 2D curve and then do a boolean operation and that handles a bunch of work for you - the booleans handle extruding the 2D shape into a "side wall" cutting object, trimming things and throwing away the right pieces, and then joining those pieces back into a solid so that's a lot of individual steps that you don't have to do when you use the booleans.

It looks like you were previously trying to do a bunch of those steps manually, maybe including even projecting the curve onto the solid before trimming with it? Even that projection step would be extra actually since Trim also has built in projection in it, you usually only need to do projection manually if you want to use the curves for some other purpose than cutting, like if you want to build some sweeps with them as rails or things like that. So there are probably a whole lot of extra steps that you were doing which are not necessary at all.

- Michael

Hi Michael,

Clear ! Thank you very much for all these explanations.
Yes I watched your 3 video tuts, but maybe due to my bad English spoken understanding for sure some teached stuff you told was lost for me...
I am learning English spoken a bit more with audio books, so I hope this will be resolved soon enough O:-)

About what interest us here, I have almost what I needed except one : how can I bolean-cut perpendicularly to my inclined surface in my example ?
Say I need to cut the ellipse perpendicular to the side, but as you know my piece is not straight (surface is curved a bit) nor vertical

So what is the best and clever way to project my cutting bolean axis perpendicular to what I have to cut ?

Cordially,
Guy

Hi Guy, the boolean will cut based on the orientation of the 2D curve, so if you need the cut to be angled you just need to rotate the curve to the angle you require and then use the same steps I described above, you don't need to do any projection this time either.

To do the rotation, go to a side view and then you can do it like this:



There I just drag the ellipse over so that it's centered on an edge of your object and then grab the rotation grip and drag it over and snap on to the same edge.

After that do the same boolean steps that I described above - select the solid and run Construct > Boolean > Diff, select the now rotated curve as the cutting object and it will make this result (also see attached 3DM file):



Hope this helps!

- Michael

Another method
For your ellipse : be sure your big surface is entierely plane
draw the ellipse entierely on the surface, then size it as needing, and move it to the place wished with the helper lines and direct snap enable + gride disable
like this you must be sure that is // to the surface so perpendicular for the Boolean diff ;)

Hello,

Many thanks for your explanations Michael, this lets me understand and learn a bit more :-)
Both methods (yours and Pilou's one) was very good to make my ellipse perpendicular to my surface.

However I prefer to draw directly on the surface with "object snap" enabled because this surface is not really planar, so drawing directly onto it lets the ellipse axis (say hole axis) exactly perpendicular just as I needed.



Thank you very much again for your so precious help ! :-D

Best thinking and cordially yours,
Guy

<< because this surface is not really planar, so drawing directly onto it lets the ellipse axis (say hole axis) exactly perpendicular just as I needed.

You can have surprise if your "surface is not surface really planar" !
In this case you must take some true marks (repères) somewhere!

(A moins que que " not surface really planar" signifie juste inclinée par rapport aux axes ? )

You know Pilou you can draw an ellipse directly on an egg surface, which is yet less planar than my piece was here ! (I'm joking don't worry ;-)

"not really planar" means "not planar" : my surface is rounded as an extruded circle and a bit like a conic one, also.
Yes, I know, a very complex surface for a so simple piece. O:-)
Anyway as you can see on my image - showing your method at the left and Michael's method at the right - this worked well enough :-)

Well, as you have imagined to be exact the ellipse was not all round touching on the "non-planar" surface, but as you understood I just simply drawn my ellipse with its hot points in touch on the surface, then this was enough to obtain my "perpendicular axis" as well as I needed for perpendicularly cutting as it was done.

Cordially,
Guy

It's for a new concept of trimer patatoes ? :)

lol..............

Peace,
Rich_Art. ;-)

Not for potatoes, but for carrots.
And only those that are cooked.

That is a new concept.
Yes, I know, difficult to understand.
But say "thanks" because it is just for this you are still alive. And after thinking, maybe also a bit because the men in black are so busy nowadays... ;oP

Be quiet,
Guy