what am i doing wrong?



i created a large hex with the polygon tool, then created another smaller one and filled the larger one by copying and pasting it with point to point snapping into a larger group and then copy and pasting that to completely fill the larger hex. i then selected everything and clicked on "join".

however not everything is joining.

any thoughts? i've attached the .3DM file

You've got some items in there listed as "solids" trying to join with "surfaces"..


I just created a big flat plane and used the curves to trim it into the polygon sections you were looking for.

Hi Klingbeil, if I select some pieces, they show up as a solid in the "Type" indicator in the upper-right area of the window:



It's a degenerate solid though, with just 2 faces joined to each other making a kind of flat pancake with no area inside of it.

So my guess is that you had some duplication in your pattern with at least 2 faces stacked up in the same area, and you're getting those duplicates joining to one another instead of joining to their neighbors like you want.

You'll need to make sure you don't have any exactly-stacked-up duplicates in the pattern before you join it.

- Michael

EDIT: Burr wins this time! ;)

thanks guys :)

i just noticed that there were duplicate lines on top of each other from duplicating a hex next to itself and joining did not meld the duplicate lines into one entity.

how can i do what you did to make it work, for future reference?

---

btw - i'm attempting to set this up for the process described in http://moi3d.com/forum/index.php?webtag=MOI&msg=817.4

Hi Klingbeil,

> how can i do what you did to make it work, for future reference?

Well, curves will only join one end to another end, they won't join into branching patterns like you would have there if you just had a bunch of individual lines.

So instead of making a pattern of single lines, for something like that you're better off making a single surface and then replicating that surface instead of replicating individual lines. Then make sure not to repeat any surfaces exactly on top of each other, that's what seems to have caused the problem in your original pattern.

Let me know if you still have any problems getting it set up.

- Michael

well... i think i'm missing something somewhere



here's how i did it this time:

1) created the large hex, created the smaller hex, selected the small hex and clicked "planar"
2) filled the larger hex with the smaller surfaced hex
3) trimmed the smaller hexes and removed the larger hex frame
4) clicked "show points"

i tried joining everything and then showing the points but nothing happens.

Hi Klingbeil, could you maybe describe a bit more about kind of end result goal you're trying to achieve, like why is it that you are trying to turn on control points?

Control points can be turned on for an individual surface, but if you have multiple trimmed surfaces joined together, control points for something like that will not turn on, since it would be kind of easy to pull the surfaces apart so that there is a gap at a place where there used to be a shared joined edge.

Are you possibly thinking from a polygon modeling viewpoint? NURBS modeling with trimmed surfaces is a really different kind of structure than polygon modeling - often times with NURBS models the edges that you see in the model are "trim curves" which are not actually defining the surface but are instead marking areas of the surface as being holes or trimmed away areas. The trim curves live on the surface but they don't actually define the shape of the surface, there is an "underlying surface" that does that. So when you turn on control points you are turning on control points of the underlying surface. This is very different than a polygon modeler - in a polygon modeler all the edges that you see are what actually defines the polygon surface, they aren't a separate thing from the surface as with trimmed NURBS.

So with trimmed NURBS you aren't free to just grab any edge you see and pull it around, but on the other hand the benefit that is gained from trim edges is much better cutting and boolean operations, because when you do a boolean between 2 objects the surfaces themselves stay the same and only new trim curves are created on them. When a polygon modeler tries to do booleans it has to actually dice up surfaces into smaller and smaller little fragments, it's one of the reasons why there are problems with booleans in polygon modelers.

Also see this FAQ answer for some more details on why show points is not working for your joined object:

FAQ: Why does show points work for some objects but not others?

- Michael

Hi Klingbeil,

> i tried joining everything and then showing the points but nothing happens.

Just to clarify - this is normal behavior, if you look at what points you were actually getting before you did the join you should be able to see that the points for each little hex are actually 4 points of a simple quad plane surface that is somewhat larger than the hex itself.

So 2 neighboring hexes that share a trim edge don't actually share surface control points in common - that's why when you join them it won't let you turn them on because if you pulled one of them it would yank the surfaces apart at what was supposed to be a joined shared edge.

You can show points on totally separate surfaces that are not joined to one another, or in some other special cases like on a box where all the surfaces that are joined actually have control points in common in their underlying surfaces.

- Michael

i'm trying to do this http://moi3d.com/forum/index.php?webtag=MOI&msg=817.4 with a hex instead of a square

Just to illustrate further with your particular file - take these 2 adjacent hexes for example:



If you turn on control points for that selected hex, you'll see that the points are actually 4 corner points somewhat larger than the hex itself like this:



That hex is a trimmed surface - the "underlying surface" is a simple 4 corner plane and the hex edges are trim edges that are marking the outer boundary of what to trim away from the outside of the plane to make the final shape.

When you manipulate those control points, you are manipulating the shape of the "underlying surface" plane, like for example dragging the corner point will do this:



Notice there that after dragging that point there is a gap opened up between the hex pieces - that's why points do not show when you have joined pieces like this together, because dragging on them would normally open up holes between what was supposed to be a shared common edge.

If you turn on control points for the other surface, you can see that the control points of the 2 surfaces are not really aligned or touching with one another in any way - it's the trim edges that actually touch each other:



Hope this helps explain it!

- Michael

Hi Klingbeil,

> i'm trying to do this
> http://moi3d.com/forum/index.php?webtag=MOI&msg=817.4
> with a hex instead of a square

NURBS surfaces are fundamentally quad-like in structure. Whenever you have a surface that looks like it has more than 4 edges on it, those are actually trim curves cutting away some base quad-like surface.

It's not quite the same as a polygon quad because the "NURBS quad" is like a sheet of rubber and can be all bendy and have a lot of points in it instead of just 4 corner points, but every underlying surface is made up of a row and column quad-like grid of control points.

You can have edges of the surface squished together into a point, that's how for example spheres are made - those are quad-like surfaces that have their top and bottom edges all compressed down to a pole point.

To get something like that link but with a hex shape would involve making a similar kind of "pole" point as a sphere, with the pole at the center of the hex. You can use Rail revolve to make a shape like that, draw a line from the center of the hex to one edge, then select the line as the profile, run rail revolve, pick the quad as the path, and give a revolve axis vertical to the hex plane, and that should build a revolved hex surface with a squished together edge at its center. It will actually be split up into 6 different surfaces since there is a creased boundary around the outside and surfaces are split into multiple pieces at any sharp edges like that. Also you'll need to turn off the "Cap ends" option in Rail revolve so that it doesn't put a second plane surface joined on to it - it thinks there is a planar opening at the bottom since all the open edges are on the same plane.

I've attached a hex created in this manner - if you turn on control points for it you'll see that it actually has points at all juncture points instead of being trimmed.

You can build a repeated structure out of this tile and join them together and still get control points to turn on (until you do some boolean or trim or something that introduces trim edges instead of natural surface edges), but these are actually little separate triangle facet pieces and won't be a single big smooth surface when you distort their points unlike that example in that link.

- Michael

aaaaah ok i see now. sorry, i'm still in a Sketchup mindset. that's why i tried making everything with lines first, to intersect the surface and have each point of the hex be control points for raising and lowering. that's the way Sketchup's sandbox works. it's clunky, but it gets the job done. however it does create objects with facets (which shows in the CNC'ed parts) and OMG does it take a lot of processing power when there are a lot of points.