Join does not work...- please help

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 From:  rayman
911.1 
I set up this form using hexagons and used the line tool
with snapping on to fill in the rest of the form.
I think there should not be any open gap so the join
tool should actually work.... but it does NOT.:(
I tried to show someone at the Caligari forum how beatifilly
Moi works to do that kind of thing ... and then I fall int this problem
Any help ß
Here are the worksteps and the file

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 From:  EdwinKlijn (EDWINTSI)
911.2 In reply to 911.1 
If you zoom in on the model you can see the points aren't aligned very wel.
One way to solve this is to 'show points' and move (snap) them together.

EDITED: 15 Oct 2007 by EDWINTSI

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 From:  rayman
911.3 
Hi Edwin !
No ! what you have there if you look at it
is the lines from the front and the lines from the backside.
I zoomed in at a few enlargements and did show points
and see yourself here its just ! point and still does not join.
There must be something else...
see the enlargement here ...
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 From:  Michael Gibson
911.4 In reply to 911.1 
Hi Rayman - it looks like you are trying to join all the curves together?

Curves in MoI can only be joined end to end to form one loop, you can't join curves to make branched structures.

So once you've got a closed curve, you can't join anything else to it, that's why it isn't working for you there.

I'd recommend separating everything out into individual segments and then selecting one loop of segments at a time and running Construct / Planar to build a face there. It isn't necessary to join as a separate step.

Once you have built all the faces then select the faces and use join to make them into a solid.

It looks like there is some additional problem here though, I'm taking a closer look at why some faces aren't building.

- Michael
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 From:  Michael Gibson
911.5 In reply to 911.4 
Hi Rayman - some faces can't be constructed with Construct / Planar because although they touch end to end, they are not all flat in a plane.

For example, these 5 lines here:



When viewed from the front view look like this (dashed construction line added to show what would be a straight edge):




So even though things touch end to end everywhere, this is not actually a polyhedron shape since the faces are not flat.

It is actually harder than what it seems to construct an accurate polyhedron - I'd actually recommend doing it by drawing a pentagon flat on the plane and then using Transform / Rotate / Rotate axis to swing it up by the exact amount needed, I'll try to cook up some steps to demonstrate.

- Michael

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 From:  Michael Gibson
911.6 In reply to 911.5 
I think that the kind of polyhedron that you're trying to build here doesn't exist.

Here I have attached the polygons for the top hex face and pentagon sides - now you can see that these do not line up to create a regular planar hexagon between them (look at it from the front side to see the non-planarity).

You could fill in those hex areas with triangles or something, but it doesn't seem like it is possible to make all simple big regular polygon faces with this arrangement.

If you use a 5-sided base instead of a hexagon base at the bottom, it is possible to create a 12-sided dodecahedron...

- Michael
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 From:  Michael Gibson
911.7 In reply to 911.6 
This seems to be about the closest thing that is possible.

If you try to force the hex faces to be planar like you did, that will result in non-planarity in the pentagon faces.

If you try to force the pentagon faces to be planar like I did, that results in non-planarity of the hexagon faces around the sides.

The angles don't work out for both to be planar at the same time - only certain arrangements of polygons can be made into stuff like this.

- Michael
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 From:  rayman
911.8 
Hi Michael !
Thank you very much for your help !
I managed to flatten out all sides in topmod and delete the edges.
This is a realy good complement to moi3d
if you look at the picture you can see
i even managed to shell it.
The files (obj) for both the basic form
and the shelled are included within this
post.
thank you very much
The basic form is a macro molecular form called Clathrin
Best regards
Peter

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 From:  Michael Gibson
911.9 In reply to 911.8 
Very cool Peter, that turned out great!

If you need to make more things like this, let me know and I can give you some more detailed instructions on how I built that one.

The basic approach is to place the polygons flat down on the plane, and then use Transform / Rotate / Rotate axis to swing them up. But the tricky part is getting the angle for how far to rotate it, that requires setting up several intermediate curves and intersecting them.

- Michael
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 From:  rayman
911.10 In reply to 911.9 
Michael !
That was work of genious what you did !
I tried to replicate what you did and
it is tricky ! that would be a very good
object for an advanced manual (tutorial) ! : )
Thank you very much.
I will come back to your offer when I run into
another example
Best regards
Peter
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 From:  Michael Gibson
911.11 In reply to 911.10 
Hi Peter, I think I figured out how to describe it in not too many steps, sort of.

Starting with a hexagon centered at the origin drawn using Draw curve / Polygon / Center, then I drew a pentagon along side of it using Draw curve / Polygon Edge, to make this:



We're going to eventually use Transform / Rotate / Rotate axis to swing that pentagon up along that shared edge. The tricky part is to figure out what angle to rotate it by, we will need to create a few shapes to create a snap point right at the angle we need so we can snap on to it during the rotation.

To start with, draw this line, which extends the rotation edge a little ways:



Now a second line that drops from the point of the pentagon perpendicular to that extended pivot axis:




Imagine that point of the pentagon as it pivots around that shared edge between the hexagon and pentagon - as it swings around the edge it will follow a path of a circle - we're now going to draw that circle by snapping on to the ends of that perpendicular line that was just drawn, checking the "Vertical" option so the circle comes up vertically from the plane:



Ok, so that circle is the path that corner of the pentagon will follow as it pivots around the shared edge. Now repeat this whole sequence with a second adjacent pentagon, to get this:



The point where these 2 circles intersect is the point where you want to rotate up to - this is where the 2 adjacent pentagons touch exactly as they swing upwards.

Now you can select one pentagon, and run Transform / Rotate / Rotate Axis. This command allows you to rotate objects around any axis line that you pick by clicking 2 points. In this case the axis will be that shared edge between the hexagon and the pentagon, and then the first reference point is that one corner of the pentagon where the circle starts at, and the second reference point is that intersection point between the 2 circles. That will create this:



Now everything else can be erased, and you can select that pivoted pentagon and use Transform / Array / Circular to make 6 copies of it:



These polygon curves can be converted to surfaces by using Construct / Planar, and joined into a combined piece using Edit / Join. Mirror it over to make a top piece.

- Michael

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 From:  Michael Gibson
911.12 In reply to 911.11 
I think this one would be quite a bit easier to describe in a video type screen capture, I hope to get started making those in not too long.
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 From:  rayman
911.13 In reply to 911.11 
Thank you very much Michael !
This is a fantastic explanation .....
It would make a very good tutorial on how to use guides
to construct difficult shapes. I learned so much from you
with this mini tutorial . I will think of using guides more
for construction in the future.
Best regards
Peter
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 From:  Michael Gibson
911.14 In reply to 911.13 
You're welcome Peter!

Yeah, the intersection snap makes a lot of accurate constructions possible, for creating stuff at particular angles, etc...

But often times the difficult part is figuring out exactly how to set up the stuff to intersect with each other though.

- Michael
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