Hi David,
Just some notes... Your curves are kindof "scewed" around differently, which is making a surface structure kindof bent or twisted and can lead to problems.. Turn on control points for that surface and review them.. Getting them to be more uniform can help with your process further down the road.

The trimming curves doesnt go all the way up to the top of the surface.. If you look at the front view and zoom in, you will see a gap at the top area.. You could run extend on those ends to get them to go all the way up.. I could then trim out that area by extruding the curve through and doing a surface/surface trim... However, I would rework a few things here before moving on...

Lyes model may be something you want to review...

Hi David, are you trying to cut the surface with this curve here? :



A couple of different problems - one is that the surface kind of sags a ways away from the curve, if you look at it from the side a bit you can see this:



For a curve to cut a surface it's best for the curve to be either a 2D planar curve which will then project on to the surface by the perpendicular direction from its plane, or for the curve to be actually right on the surface instead of kind of a ways off of it like this currently is.

Then in addition to that, it looks like the ends of the trimming curve don't quite reach all the way to the edge of the surface (like Burr already mentioned, I just saw), which means that the curve will not fully divide the surface into different regions. You can see this if you zoom in to this area here:


So note there that when zooming in the curve is just a little bit shy of actually hitting the surface edge:



You want cutting curves to extend all the way to the surface's boundary to make sure that they will be able to cut the surface into distinct pieces. It's ok to actually make a cutting curve overshoot the boundary a bit, so you may want to do that just to make sure that it fully divides the surface.

I've attached an example 3DM model file that has a curve that should work to trim your surface now. I took your curve and flattened it in the Top view (just grab one corner grip on the edit frame that shows up when you select things and squish it down until you get the "flat" snap), so that it would be planar and project on to the surface, and then I turned on control points and grabbed the end 2 control points and pulled them up so they crossed the surface edge like this:



So with this version you can select the surface and run the Trim command, then select the cutting curve - that will then divide the surface into 2 regions, then you can select which region you want to have removed and right-click to finish the Trim command.

- Michael

Michael,

Thanks for taking the time to explain this to me.

The next step I had envisioned, after deleting the hightlighted trimed surface was to use the edge of the new "hole" as one rail of a Sweep to create an inside wall for the air scoop. I discovered that I don't have the option to do this.

I need to better orient my thinking on how to use the software for this problem but being a newbie, I'm still learning.

Thanks again.

Hi David,

> The next step I had envisioned, after deleting the hightlighted
> trimed surface was to use the edge of the new "hole" as one
> rail of a Sweep to create an inside wall for the air scoop. I
> discovered that I don't have the option to do this.

But yes actually you can do that - any edge can be used as an input curve to surfacing commands like sweep, extrude, revolve, etc... - so you can draw a little curve coming off of that hole edge and then select it and run sweep and select the edge as the rail path curve.

If the edge is fragmented into some pieces, you will need to do a bit of preparation work - either select the multiple edge pieces and then run the Join command to create a new curve that has those pieces joined together to use as the rail, or you can also use the Merge command to merge together 2 edge fragments that touch each other and are smooth where they meet:
http://moi3d.com/2.0/docs/moi_command_reference10.htm#merge

I've attached an example file where I've drawn a little curve hanging off the end of the hole - select it and then run sweep and select the edge as the rail curve.

You may want to place curves at both the start and the end of the rail in situations like this so that you have direct control over how the sweep is shaped at the ends of the sweep.

Was there some reason why you thought that you could not use Sweep along the edge of the hole?

- Michael

Michael,

Thanks to your email- the problem is solved.

The problem I was having is that after the trim/delete is done the newly created curve did not highlight when moused over
as other curves or lines do. I didn't initially understand that the network needs to be highlighted first before the curve(s) will highlight.
This may have been because, as you pointed out, the new curve was fragmented. Once I did a Join on the two segments, the new curve
would highlight as any other curve does.

Looking forward to completing the project.

Thanks again.

Hi David... There is a difference between curves and "surface edges"... To select a surface edge you need to do a "drill down" pick, which is as you describe, selecting the surface then the second pick will target that surfaces edge.. The same is for the faces of solids or joined surfaces.. Select the object then the face will become selectable.. The edges take precedence, so you may have to zoom a bit on smaller faces to be able to target them...

Hi David, yup Burr has described that well - selecting edges is a bit different than selecting a "standalone" curve. To select an edge you first do one click on it to select the "whole object" and then a second click will drill in to select either edge or face sub-objects.

That gives you a method to control selecting either an entire solid (with just the first click) or also going in and selecting sub-object pieces with the secondary clicks.

Check out here for some description of how selection works:
http://moi3d.com/2.0/docs/moi_introduction.htm#selection

- Michael