1. ## BooleanDifference question

Hello All,

I have a simple boolean question that I cannot resolve. I have attached the file (.dwg) for reference. It is supposed to be a simple column made by drawing the 2D form and revolving it around the central axis. I then drew one of the flutes and attached it to the column. I want to make 12 of these equal distance from each other and the use BooleanDifference? or whatever to remove this material from the column. The message I got back was "unable to complete boolean operation". There is probably a simple reason for this, but being a newbie, I don't know what it is. Can anyone help?

Thanks,

ChuckInCR

2. I would place the flutes in position and intersect the flute and column surface then use the trace created by intersecting the surfaces to trim the surfaces... keep in mind you are dealing with "polysurfaces" and not solids... also you may have to show more isolines to make triming easer...

Hope this helps... James

3. Yes, your geometry has to be solid to boolean.
You can trim, join and other operations to the wireframes and surfaces, but the boolean operations are for solids.

In Rhino a solid is considered: a joint surface or polysurface that is airtight and has no gaps. As an experiment, you can make a 3d Box, Explode it, Join the parts and turn it back Solid/Make Solid.

1.) To make the cap, it looks like you want to join your radius and straight section, and then revolve that using the profile and picking axis points going anywhere through the column centerline.

2.) You can make that surface you just made a solid by Solid/Cap Planer holes. (or the hard way by doing a surface/planer curve, selecting the bottom edge, and then Join, and then Solid/Make Solid.)

3.) As for the cylindrical column, you can you a cylinder in place of the round wireframe situation...

4.) As for the flutes, you can make a single tool to carve flutes by drawing spheres on either end halfway on a cylinder, and then Solid/Union/ adding them to the ends of cylinder.

5.) You can position the tool you just made, sinking it into the big column from 3.) , and THEN do your Solid/Difference. Check your "Delete input" options on the command line.

For the rest to the flutes, you can use Transform/Array/Polar to create the rest going around the column, or you can paste them, and rotate them using angle snaps, if you prefer the challenge.

Besides booleaning the top to the column, that should do it.

[Alternatively, if the final boolean differences don't give you what you want you can create the geometry by building it from surfaces. You can extrude the curve flute profile, and then revolve the top and bottom radii, and finally using the flutes profiles to cut a cylindrical surface, and using the surface to trim the flute channels.]

If you have Rhino 4, the incremental save is a good way to make sure you don't loose any work by taking a long dead end path. I have set an Alias for CTRL-B, ( "B" for bump,) to save a new file. There's usually more than one way to make somthing, and some are better than others. You can also start the traditional junkpile right in the map, layers help keep the visual confusion to a minimum.

4. Yes, your geometery has to be solid to boolean.
This is inaccurate. Rhino will Boolean open objects as well. Solids (closed valid polysurfaces) work more predictably for the newbie because the surface normals always point to the outside. If the normals are pointing in the wrong direction, you might get the inverse of the result you wanted (the part to be removed is left, for example).

But Boolean operations also work predictably on open objects once you know what direction the normals need to point. Or, if you have only two objects, you can call Boolean2Objects and cycle through all the possibilities.

Boolean operations will fail if Rhino does not find a complete intersection with which to cut the two (or more) parts. If a BO fails with two "solids", the first thing to do is run Intersect and see if the intersection is complete, usually it isn't and the gap/overlap will show you where the problem is.

http://en.wiki.mcneel.com/default.as...ooleanFAQ.html

--ch

5. I found that I had to take your curve info and re-do using new curves, extrudes (capped), then som constructs, and sweep1 stuff to make viable solid. try this file. sorry i could not send file. I use winRAR to compress not zip. email me and I'll send the 3dm file.

6. Originally Posted by chmillman
This is inaccurate. Rhino will Boolean open objects as well. Solids (closed valid polysurfaces) work more predictably for the newbie because the surface normals always point to the outside. If the normals are pointing in the wrong direction, you might get the inverse of the result you wanted (the part to be removed is left, for example).

But Boolean operations also work predictably on open objects once you know what direction the normals need to point. Or, if you have only two objects, you can call Boolean2Objects and cycle through all the possibilities.

Boolean operations will fail if Rhino does not find a complete intersection with which to cut the two (or more) parts. If a BO fails with two "solids", the first thing to do is run Intersect and see if the intersection is complete, usually it isn't and the gap/overlap will show you where the problem is.

http://en.wiki.mcneel.com/default.as...ooleanFAQ.html

--ch

If only you spent as much time in helping the person who asked for your help.

7. If only you spent as much time in helping the person who asked for your help.
Hmm... I thought I was helping by providing more accurate information.

I don't always have time to do examples, especially when the procedure has already been described. Attached is a file with the steps I would take to do this. Use the Notes command to see the steps if the notes window doesn't open automatically.

Note that there are a number of other ways, and a couple of them looked like they should work but didn't - for example, the same basic operation but using Pipe with round ends to create the cutter failed. So I assume there might also be a bug or two there, which has been duly posted to the Rhino newsgroup.

Hmm, who might have written that Wiki article? How long did that take? --ch

8. Making a tool from a cylinder and two spheres worked as a difference tool in Rhino 4, I only did one subtraction, though.

9. "There's a lot of ways to skin a cat in CAD."