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Booleans leaving gaps in geometry
Posted: 23 September 2013 02:18 PM   [ Ignore ]
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Been tearing my hair on this one. I’m trying to learn how to use hexagon and model a camera. I have a plate I want to cut holes in where dials and indicators go.

The cuts create quite a complex geometry That all seems to be fine but afterwards when I add thickness there are very small gaps. You can see them as dark lines under lighting in the attached image.

Rapidly running out of ideas. Does anyone know of a way of doing this that will work?

Thanks,

Martin

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Posted: 24 September 2013 03:18 AM   [ Ignore ]   [ # 1 ]
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1
Try to post pictures where you see geometry
2
Use with care Boolean operations
3
Better shape and do not use Boolean operations
4
Use Boolean operations only in cases of extreme necessity.

Sorry Inglese

Bye

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“Il principio della scienza della pittura è il punto, il secondo è la linea, il terzo è la superficie, il quarto è il corpo che si veste di tal superficie”
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Posted: 24 September 2013 03:08 PM   [ Ignore ]   [ # 2 ]
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Ok thanks but I don’t see why cutting a 2d surface creates these problems. I was going to try to recreate this in Blender but I see it can only do very basic booleans, not the surface intersections that Hexagon can do.

BTW it’s hard to post pictures that show the problems because the end result has a lot of lines that converge on one of the corners and it’s impossible to see the gaps in wireframe. I only saw the flaws when I turned on lighting, like in the images I posted.

Martin

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Posted: 24 September 2013 11:46 PM   [ Ignore ]   [ # 3 ]
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Hi there:)

Are you sure those are gaps - look more like flipped normals to me.  Try unifying the normals; see if that will fix.

Boolean operations are always a gamble - in any software, except where it is specifically designed for it.

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Posted: 25 September 2013 12:31 AM   [ Ignore ]   [ # 4 ]
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msmith9999 - 24 September 2013 03:08 PM

Ok thanks but I don’t see why cutting a 2d surface creates these problems. I was going to try to recreate this in Blender but I see it can only do very basic booleans, not the surface intersections that Hexagon can do.

BTW it’s hard to post pictures that show the problems because the end result has a lot of lines that converge on one of the corners and it’s impossible to see the gaps in wireframe. I only saw the flaws when I turned on lighting, like in the images I posted.

Martin

With Boolean operations have made ​​the “booleanchezzal” but I had to use a lot of faces.
Not comfortable.

 

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“Il principio della scienza della pittura è il punto, il secondo è la linea, il terzo è la superficie, il quarto è il corpo che si veste di tal superficie”
Leonardo da Vinci

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Posted: 25 September 2013 04:02 AM   [ Ignore ]   [ # 5 ]
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Booleans in Hexagon can create all sorts of strange geometry and the “Create Thickness” command does seem to highlight them. It’s best, if possible, to add any thickness first before using the Boolean commands so you are starting with a fairly simple shape.

I’ve found that other software will often add thickness correctly to items exported from Hexagon as .obj files that Hexagon itself makes a mess of but this is, obviously, only a solution if you have access to more than one programme. I swap between Hexagon and Strata 3D which compliment each other nicely.

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Posted: 25 September 2013 04:12 AM   [ Ignore ]   [ # 6 ]
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With all 3D mesh modelling packages you need to create your initial mesh from lots of polygons, then do the Boolean, then do some clean up of vertices, then add thickness.

Booleans work beautifully in 3D CAD (nurbs) packages but most artists try to avoid Booleans in the mesh modelling packages like Hexagon, max, modo etc because you can get issues like you have above if they are used incorrectly.

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Posted: 25 September 2013 12:02 PM   [ Ignore ]   [ # 7 ]
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Thanks for the replies folks. I don’t think it’s normals though that was a good idea, they look like incredibly small gaps. I’ve tried adding the thickness before and after cutting and got essentially the same result.

Can someone suggest a better way of creating an object with circular holes through it?

Thanks,

Martin

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Posted: 25 September 2013 12:06 PM   [ Ignore ]   [ # 8 ]
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One thing that comes to my mind:

Delete a few polygons where the hole should be and then move the remaining ones around so that the hole becomes round (or what ever shape you like).

Ok, probably not the best solution, but should work grin

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Posted: 25 September 2013 01:04 PM   [ Ignore ]   [ # 9 ]
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Here are several suggestions.

1.  The easiest is to fake it by painting a alpha channel “hole” in your texture map.
2.  A method I call “fake Boolean” for want of a better expression.  Basically, a perfect square becomes a perfect circle when smoothed.  See pic - A extrude inwards on the top and bottom of opposing polys - be sure to get a perfect square.  B bridge the two polys - you get a hole.  C Smoothed
3.  Delete the polys where you want the hole - draw a circle, extrude it outwards to make a mesh, marry it up to the surrounding mesh, do the same at the other end and bridge..
4.  Start off the mesh with circles, i.e. model around the holes.  Extrude them outwards to form meshes, join them up and continue with the rest of the modelling.

If you need further info on any of these, just ask smile

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Posted: 29 September 2013 10:46 PM   [ Ignore ]   [ # 10 ]
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To create a surface with a hole in it, I follow this process.

- first create the mesh you want to put a hole in. This process works best if the surface you are drilling is planar.
- select a square of 4 quads (2 x 2) where you want the hole to be and delete those quads. If your hole has to go through, delete the corresponding 4 quads on the reverse side of the volume.
- create a cylinder with 16 edges around.
-extrude the edges of the cylinder with the fast extrude tool. Scale thevertices of the new faces so that you square up the newly created ...
oh stuff it.

Look wait a while and I will have some pictures for you.

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Posted: 29 September 2013 11:27 PM   [ Ignore ]   [ # 11 ]
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Right, here are the steps

1 - create the model you need a hole in
2 - make sure there is enough resolution in the mesh, though you could do this with 1 quad
3 - delete the faces where you want the hole to be
4 - create a cylinder - this will be the geometry of the hole - size it to suit your needs
5 - extrude out the edges to make a thred bobbin shape.
6 - select vertices and scale the relevant dimension to 0, to create a square shape - this step is actually optional, come to think of it
7 - weld the extra vertices to the centreline or corners, as you wish. Before doing this, add any fillets or chamfers you want.
8 - weld the hole geometry to your model
9 - weld the vertices together so the surfaces are stitched together
10 - ta-dah!

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Posted: 30 September 2013 11:46 AM   [ Ignore ]   [ # 12 ]
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search youtube for tutorials by EZ he has tuts specifically for what you want. its ez when he shows it

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