View Full Version : General Boolean Questions

12-09-2003, 05:54 PM
I'm sure the way i'm looking at this is all wrong! After creating a wall (for a house let's say) and all my boxes for my window or door cut outs, I go to do a boolean subtract, and the face of the wall doesn't get cut out, only the sides are left between the walls. Are there tutorials on basic booleaning anywhere? Also Sometimes i'll cut an area out and I have to manually delete the polygone in the negative area. It's things like this that make me think i'm not looking at this right. I'm doing a lot of geometric buildings and simple structures with simple cut outs.

Any 101 advise?

12-09-2003, 10:37 PM
Make sure that on your wall, all of the polys are facing you and not flipped the wrong way. You can see this from the normals sticking off of the polys. Make sure the polys on your cutting objects (door squares, window squares, etc..) also have their polys facing you.

Hit the f key and you can see the result of the polys facing the different directions.

I, sometimes get the result you are getting and 99% of the time it is from polys being flipped the wrong way on my cutting objects.

You may have to manually select individual ones to flip, but usually it is 'f' with none selected to flip them all.

12-10-2003, 02:54 AM
Also, if you have some really distort polys on your object, this can affect it too. It's best to Triple any really non-planar polygons and then Lw can calculate it a bit better.

12-10-2003, 04:15 PM
Thanks For your responces. I understand about the polygons being flipped, but I still get the same problem ( I even double checked, to make sure). If I knew how to take a screen shot on my windows 2000 system I would, and post it, i'm sure that's always helpful. Anyhow Thanks again and I'll keep tryin. Maybe someone out there can tell me how to take a screen shot on the ol PC.

Oh yeah, when I triple the surface, then try to subtract my background layer with boolean, a positive appears in the forground layer instead of a cutout.
what's up?

Okay.okay, (i'm talkin to myself now), the tripleing did work, my polygons must have been irregular, I only tripled the front of the wall when I didn't think it was working, now it's cool.

Thanks for your replies, forgive my ignorance, and it was cool to post a message, 1st time, This Forum thing is really cool. Maybe i'll figure out how to post a cool animation next to my name too. Fun stuff, thanks again to all of you out there on the other side making this community possible.

12-10-2003, 05:12 PM
To take a screenshot, press 'Print screen' button on the top right of the keyboard, or alt-'print screen' for a screen shot of the currently selected window.

To add a cool animation, convert your anim to an animated gif, then edit your User CP>editoptions>avatar and use the browse to load it off your pc :) Heed the size/memory size limitations, and it'll work :)

12-10-2003, 06:20 PM
It took me a while to figure out where it went after i took the shot but i found it there on my handy dandy clip board.

12-10-2003, 06:51 PM
Couple basic things to remember about booleaning..

1. Always make sure a cutter object overlaps the target object. If the cutter is just resting on the target object you can get problems..

2. If you're trying to do something extremely complex, such as chopping several cylinders out of a box, it might fail.. solution is to divide the target surface into two (or more) polygons so that your cutting objects are operating on different polygons..

12-11-2003, 12:51 PM
if at all possible avoid booleans like the plague.They are inherinatly problematic.

I used to boolean my butt off back in my Truespace days(ancient history) and then someone told me to try and stay away from booleans and I finally saw why.There is too much funkyness that can happen and you might not know it until its too late and wind up with a screwed up model.

Booleans are obviously okay sometimes but I think if you model your way around having to use them then the better off you'll be.And you'll be a more experienced modeller : )

12-11-2003, 03:39 PM
That's good advice batzilla, i will ponder that more often when i'm solving a modeling problems in the future. Working with archetectural models a lot of times it's hard to get away from thinking of booleans as a perfect solution.

12-13-2003, 04:33 PM
Here's a some more boolean basics:

1) Both the cutting object and the target must be CLOSED shapes;
2) The operation will get confused if there are stray or overlapping points in the mesh. Do a merge on it and clean out any other unneeded points or polys;
3) You can help things out by selecting just the polys which directly overlap the intersection of the 2 shapes.
4) Always do a merge after a boolean to clean up, check for polys made non-planar, etc.

If what you are trying to do doesn't pass the 1) test, look at Drill and Solid Drill instead.