Hi,

Been playing around now with MoI for a bit and now want to push myself with more complex situations after seeing some great examples of more complex models.

Till now I have been content will basic cutting and joining of solid shapes as advised but I think (I maybe wrong) to get complex subtle intricate models one has to start playing around with joining surfaces created via Loft,Revolve,sweep blend etc to form solids :)

The first thing I want to understand is techniques to the create smooth transitions of shapes/surfaces. For example the transition between the car body to the car wing, a transition of a jet wing to the fuselage etc.

Now I have been reading posts but I confess to be getting slight confused as I'm no Cad Person (but wanting to learn :) )

I attached a a very simple example of the beginnings I want to achieve. It consists of

a) a main body created from via the Loft command
b) a joined surface created from another loft which was constructed from a projection of a eclipse on the body to a series of circles

Although this result is great (to me) I cannot boolean union these two together without strange artefacts being created

Again the question is this the correct way of going about it

Hope this post makes sense :)

Steve

Hi Steve - so really the problem in this case is that it's having some difficulty figuring out how to slice the objects together because the objects are sort of barely skimming right along one another.

It can be easier for the booleans to handle stuff if your objects actually push through each other a little ways instead of the barely skimming over each other kind of situation.

So for example if you move your side piece inward a little bit so that there it actually pushes through the other one by a small amount, you should then find it will boolean union ok.

Another thing you can try is if you have a problem with booleans figuring out how to do stuff you can try to use Trim instead, which in some ways is a bit more simple of an operation, particularly when using curves.

In your case here if you use Trim to cut a hole in the object using the edge curve of the other one as the cutting object you can get a result like this (I moved one piece a little so you can see how I made the hole):



Then after doing that I used Edit > Join to join those 2 surface objects together into a full solid, see the attached 3DM file.


But basically the boolean operations are focused on trying to intersect objects to find cutting areas, and then they decide which pieces of things to discard according to what volume they are in.

But 2 surfaces that just barely hug right along each others surfaces can be a lot more difficult to intersect - it's hard to see it but in your case there, it will actually have a really slight amount of undulations where some areas of the surfaces are slightly apart from each other and some areas are pushed through one another. If you make it more all pushed through then that simplifies things for the intersection calculations with the booleans.

Also it won't always be an issue - there are a lot of cases where skimming surfaces for booleans can also work ok, and I suppose that can add to the confusion if you've seen other things like you've built here work ok before - but it's just generally a more difficult kind of calculation for the booleans to handle so it's better to try and make things push through a bit more as a best practice to give things the best chance of working more smoothly.

Hope this helps,

- Michael

Another workflow possible
move -10 the wing on X axe
Copy move 10 the big round wing curve to the fuselage
Trim fuselage + big curve
kill the fuselage surface intersection + big curve
Move 10 the Wing on X axe
Boolean union all

PS Just type 10 in the box number Entry d before makes the moves ;)

And basically the strange artifact is a result of the booleans not getting a full closed intersection curve at the juncture point.

If you look at the weird result on the main body you'll see that there are some places where there are not any edges, like here:



So the edges that you do see there are sort of more like little infinitely thin slits cutting the surface, rather than it having a full closed boundary making a proper hole there. Probably your side surface is just very slightly hanging to the outside of the main body in those particular areas.

If you move it over just a little bit so it pushes through, it will help make the 2 surfaces have a cleaner intersection between them - that's basically why having things push through each other a little bit instead of skimming can help.

- Michael

Hi Steve, also you wrote:

> but I think (I maybe wrong) to get complex subtle intricate
> models one has to start playing around with joining surfaces
> created via Loft,Revolve,sweep blend etc to form solids :)

And no, you're not wrong about this - for a lot of types of more complex models particular ones that have swoopy parts instead of blocky stuff you will be creating some portions out of a freeform surface command like Sweep and then incorporating that into part of your model.

I guess the main trick is that if you're planning on combining the pieces together by booleans and then putting fillets between them, it's easiest to make the pieces push through each other rather than barely skim right along each other. In a certain sense making things push through each other can simplify things a bit as well because you don't have to worry quite so much to set things up, you just let excess parts get sliced off and let new common edges between pieces get created by intersections.

- Michael

;) No artifact for me :)

Thanks for your help.

This really did help me out here !!



Michael using the trim and join workflow did help me out here I must make a mental note of this.

For some dumb reason I thought only to use the the edit/trim/join when constructing the 2d curves but not once they used as part of a surface/object


Till this time I used Boolean Diff/Union is there a difference between this and edit/trim/join

Trim is more for "Surfaces" and "Curves", Boolean for "Solids" or "2D curves"

thanks my friend

Hi Steve,

> Till this time I used Boolean Diff/Union is there a difference
> between this and edit/trim/join

Trim and join are sort of more "low level" tools than the booleans.

You might kind of think of the booleans as a sort of batch mode trim & join where they do a similar job but automatically decide which pieces to discard from the trimming according to what volume they are contained inside of.

Trim will cut things up but then it's up to you to pick which pieces you want to discard, and then you will need to follow it up with a Join afterwards - those steps are basically built in to the booleans so it's sort of more convenient to use the booleans when possible (which is basically when you are working with solids).


> Till this time I used Boolean Diff/Union

You could still use boolean union in this case if you made the pieces stick through each other a little bit instead of having that side piece sort of exactly skimming along the outer surface of the main body - it's that skimming situation that the booleans are having difficulty with in your particular case here, when they try to intersect the 2 surfaces they are not getting a clean intersection result because the side surface has just a tiny amount of empty space between it and the main body in a few areas.

- Michael

Hi Steve - attached here is what I mean by moving your object a little bit over so they push through each other.

If you look at this one, the side object is sunk down a little ways into the main body instead of just skimming right along its surface.

Now you can use boolean union with it as you were trying to do originally.

It's easier for the booleans if you make pieces push through each other a little bit like this rather than making pieces that barely touch.

- Michael

right gotcha,

Thanks again Michael

Hi,

Here's another example I seem to run into quite often. I'm trying to blend/loft these two pieces together however as you see the main piece is not a clean surface it has surface lines which seem to mess up the potential blend.

What would you do in this situation?

Hi Steve - so in a case like that if you want to use Blend you have to split up the long edge into pieces so that you'll have a 1-to-1 match between edges on both sides.

You can use the Edit > Trim command to cut an edge up into smaller edge pieces - select the edge, run Trim, then click the "Add trim points" button and then you'll be able to click the points on the edge where you want it to be split at.

I will be working on upgrading Blend in v3 so that you won't need to do that anymore, but for now you've got to arrange your edges so that there is a matching pair of edges.

- Michael

Another thing you might do to make things easier would be to take this curve here which is made up of 3 segments:



Join those together and run the Rebuild command on it
http://moi3d.com/2.0/docs/moi_command_reference10.htm#rebuild

You get those additional edges in your original one because the curve that you were extruding was made up of several segments - the segmentation of the curve will come through into surfaces that you construct from it, with one face for each segment of the original curve.

So you can eliminate those interior edges by reforming the curve to be made up of just one single smooth segment instead of being multiple segments - the Rebuild command is the easiest way to reconstruct a curve like that.

Then when you extrude it, you'll see it's just one surface instead of multiple faces:



- Michael

Thanks very much Michael,

Interesting............I give this a go :)


Cheers
Steve

Hi Steve,

I have attached my approach based on your example.
Yust hide the solid and switch on the controlpoints with the Show pts command.

What i did is projected the blue lines on the shape.
Then trimmed the curves at the border and turned on the controlpoints
With Line/both sides command(see green lines)snapping on the endpoint of the mastercurve(orange) and the nearest controlpoint.
I switched on the controlpoints of the cyan colored curves and snapped the nearest controlpoint on the green lines.
At last i used Sweep/two curves.

Ps. You can play with the rebuild command(R shortcut key) to add or reduce control points.

Hey thanks my friend, very good of you to do this

Much appreciated

Steve