View Full Version : Boolean subtract not leaving behind a surface.

07-09-2013, 09:59 AM
I have a simple cylinder that I'm trying to create a hole through using subtract Boolean. My cylinder is in layer 1, my subtract object is in layer 2 and after I complete the Boolean subtract operation the hole is there, but no surface on the inside. Its as if I just completed a drill operation. Its my understanding that Boolean is supposed to leave a surface behind, am I wrong?

LightWave 11.0

07-09-2013, 10:41 AM
I just did a quick test and it worked for me.

Can you post your object?

07-09-2013, 11:09 AM
Perhaps the polys are there just flipped? Try selecting in the "empty" space.

07-09-2013, 11:56 AM
Is any part of the mesh open? Not just unweld/notMerged I mean really open hole. I was having quite bad results from this today.


07-09-2013, 12:44 PM
http://i1340.photobucket.com/albums/o728/dkurkowski42/Capture_zpsdd12ff1c.png (http://s1340.photobucket.com/user/dkurkowski42/media/Capture_zpsdd12ff1c.png.html)

Thank you for the responses.

So after I modified the cylinder to include the "fins" the polys from the Boolean appeared, even though they are backwards which I flipped (not shown in image). I checked before hand to see if there were polys, but didn't notice any (I was aware of the flipped poly issue).

Could this be a problem with a refresh rate or something similar?

Also, I noticed a line appeared on the cylinder that was not there before and I cannot delete it, weld it or merge it with the rest of the form. any ideas?

07-09-2013, 01:02 PM
Refresh rate wouldn't have anything to do with a boolean operation.

Are you trying to do a boolean operation on a sub-d object? I don't think that works.

07-09-2013, 01:31 PM
Well, I notice you're in full screen perspective. Is that for our benefit for the image? Or is that the only window you've had active?

I ask because (just spit balling here) maybe at one point you were in Texture mode where flipped polys would be invisible. And then at some point you went to Textured Wire, where, as in the image above, they would be seen.

Re the line..... maybe if you post an image highlighting the line. Perhaps it's a two point poly chain that's hard to grab. Go to statistics (w) in poly mode to find and delete.

07-09-2013, 01:42 PM
Ah! Nick has a good point.

You are obviously not in CC SubD, but you still have an Ngon on the top there. The line you're seeing is probably the meeting point of SubD and non Sub D geometry.

Quick fix.... switch to CC.
Make the Ngon all quads (hopefully the tube used in subtraction has the same number of sides as the outer cylinder) and subD.

07-09-2013, 01:50 PM
I've managed to re-create my problem.

(The perspective view was for the image)

I created a cylinder, rounded the top poly, (5 polys, mesh L, Conv. In, P. Ins. Y), then created my Boolean cylinder in 2nd layer and subtracted it. Results were, no poly's created from Boolean operation just the hole, and the mystery lines on the top and bottom poly of the cylinder. As soon as I stretch one of the outside - side polys of the cylinder the Boolean poly's appear in the view port.


I'm getting the end result I want, I'm just not sure if I'm going about it a backwards way.

Again thank you for all the responses.

http://i1340.photobucket.com/albums/o728/dkurkowski42/Capture2_zps6013b4b3.png (http://s1340.photobucket.com/user/dkurkowski42/media/Capture2_zps6013b4b3.png.html)

07-09-2013, 02:04 PM
You could have modeled this with sub'ds without the need to do booleans.

07-09-2013, 02:49 PM
That's not a "mystery" line. It's necessary geometry. U cant have a cutout in a poly without the outside being connected to the inside (it might not show up in CCs sometimes.... but it's there).

U still look like you have some funkiness in the model though (inside tube). Have you merged points? AND it looks like you've got a bunch of one point polys.

Can u post the "before boolean model" (with the subtract object) as well as the resulting lwo?

07-10-2013, 07:38 AM
very nice. I guess I need to work on my model building in LightWave. How'd you do that? :)

07-10-2013, 07:54 AM
It's basically a disc with the sides beveled out. Bevel was used on the ends as well. I used bandsaw to add more cuts where needed. The twist tool was used to bend the blades.

07-16-2013, 07:16 AM
Check out the link in my sig. Should help with information on modeling with subpatches.