Hi David, sorry it's not easy to follow just the general text description of a concave piece and a door handle, it really helps to be able to actually see the specific shapes that you're working on, preferably by attaching the 3DM model file here so it can be examined.

> I thought revolving a matching elipse and doing a boolean
> subtract would do it but that did not work either

Could you please attach the 3DM model file that has the pieces in it that you were trying to boolean so I could see what did not work in this case?

Is the door an open surface instead of a closed solid? If that is the case, then you will most likely need to use the Trim command to cut them with each other rather than using Booleans. Boolean commands are more oriented towards working with cutting a solid - if you want to cut a surface use Trim instead and Trim will allow you to manually pick which cut up fragments you want to keep or discard.

But I'm not really sure if that was what you were running into or not - if you can post the 3DM model file here that will help a lot to see what the problem was.

- Michael

Micheal,
Attached is the .3dm file. As you see, I want to cut away half the blister leaving the inside concave half.

Thanks for looking at this.

Hi David - you're running into some difficulty because the revolve was not quite done cleanly - it looks like the shape you revolved did not quite extend fully to the revolve axis.

Note that if you zoom in here you can see a little tiny additional additional surface:






Little tiny surface fragments like that will make for more difficulty when doing surface intersection and cutting type operations.

If you get your ellipse shape to be better constructed with the endpoints of the curve being revolved exactly aligned to the revolve axis instead of a little bit of space between the endpoints and the revolve axis you should get a better result.

- Michael

The egg revolve is malformed, and the "pre-trim" hole in the door doesnt match the egg also...

You can untrim the joind surfaces by running seperate and selecting all the edges and delete, then re-join the 2 surfaces.. I redid the revolve by extracting the edge of it and deleting the original, then "flattened it" with the edit fram in the top view. Then I went to the right view and used the rotation widget to align the eggs edge with the joined surfaces edge and ran trim and selected done for a trim all, then deleted the outer egg surface and the joined surfaces cap that was left behind...

Hi David - I've attached here a version with a cleaned up ellipsoid that should now work properly.

I did an "untrim" (selected the boundaries and deleted them) of the doors to get them back to their full surfaces, and for the ellipsoid I extracted the edge of the ellipsoid and did a new revolve, making sure to snap the ends of the revolve axis exactly on to the ends of the generator curve.

Now you can use the Trim command to cut the ellipsoid and the door at the same time.

To do that, select both the door and the ellipsoid. Then run the Trim command.

The command prompt in the upper-right area of the window will say "Select cutting objects or Done for mutual trim" - in this case you want to make each object both cut the other and also be cut itself, which is the "mutual trim" method. So at this stage of the Trim command just push Done or right-click in a viewport to tell Trim that you are not picking any other cutting objects.

Then there will be a pause for a moment as it calculates the fragment pieces, and then the next stage of Trim you can either just push Done to keep all the pieces, or you can pick the pieces you want to have discarded. Sometimes it is easiest to just have it slice up all the pieces and then delete the ones you don't need after Trim is finished. If you do it that way then you can use Join after you have finished deleting things to glue things together.

- Michael

EDIT: Same thing Burr is saying above...

Hi David - another thing I noticed in this model is that this surface here seems a bit odd:




If you use Edit > Separate to break it apart from the other one and then turn on its control points, you can see that its control point grid is kind of badly formed and kind of squashed together:




It looks like this was created as something like a network surface between 3 curves like this:




Usually it's better to construct something with a rounded outline like that by first making a simple broad rectangular surface (which will then have a nicely formed control point grid and not be squashed together anywhere) and then trim that surface by a side profile that has the rounded corners in it, more like this:










A surface created in that way by a more regular initial rectangular base surface, will retain that surface as the underlying thing below the trimmed away areas:




Just in general you will tend to get much higher quality surfaces with this method - the other way you can easily get ripples and bumps and even self-intersecting areas by trying to build a network directly to a non-rectangular outline like the other one.

- Michael

Thanks for the help. Following your instructions I was able to correct and complete the door.

Many Thanks!

Michael,

I finished the Audi TT and posted it in the Gallery. (but are they ever really finished?)

I have been thinking about what you said: "control point grid is kind of badly formed".
Maybe I should be thinking more about the overall shape of my object for creating Networks rather than individual parts
like doors, quarter panels, etc. I can Trim out parts later in the process, assuring a better relationship of the individual components.

What do you think?

Thanks again.

Hi David, your audi turned out great!

> Maybe I should be thinking more about the overall shape of my
> object for creating Networks rather than individual parts
> like doors, quarter panels, etc. I can Trim out parts later in the
> process, assuring a better relationship of the individual components.

It can kind of depend on the situation, but yes if you want to make something that has pieces that look like they all come from the same flowing shape, it can be a good technique to make a bigger surface and then trim the pieces out from that.

At the same time though, you generally don't want to make a surface contort and try to change shape too much between different forms, it's hard to get a good quality surface when you try to apply too much force to it to try and make it change shape too much. Areas of your model where things go through a sharp bend kind of signal an interruption in the base form, and it's not so good to try and build a network that traverses too many areas like that.

But when the pieces all look like they come from the same underlying broadly shaped form, that's a good time to use a larger surface + trimming.

- Michael