why do booleans suck and workarounds?

[Neurosys]

Seriously, have a real hard time cutting primitives I've meddled with or anything involving a cylinder. I've searched and heard a few reasons but the solutions dont work.

I know you guys have got to be using booleans at least sometimes. This was day 1 stuff back in 3dsmax (which I no longer use cuz I love blender now) but I need to boolean.

[🌴Phil337™🌴]

Don' t understand what you say but as i know you need non manifold object to use boolean

[*P0P$*FR3$H3NM3Y3R*]

I use booleans for primitive shapes, it works fairly well. It is not perfect but it works.

[Ad Hominem]

cutting a boolean into a curved surface is tricky and almost always will require you to go in there and manually clean it up. There are some paid addons that really streamline this process to a very high degree - HardOps, Box Cutter, MeshMachin3 are damn near essential for a serious boolean work flow.

I can try to help you if you want to post a screenshot of an example.

This might be helpful too, there are a couple of these topo studies on this channel.
https://www.youtube.com/watch?v=Xz4w6QXpuDo

They use these addons a bit but it's nothing you can't do with vanilla blender, the addons just speed up the process.

[Neurosys]

The best example for the cylindrical errors, I made a cynlinder, used my mearsurements to make it placeholder for a stepper motor (round, 2 flangey things with holes, 32mmx32mm) I extrude my way to the target shape and with minimal shape tampering (blender has me all nervous about this now) I arrive at the shape I want. I'm actually making a holder for the motor, so I copy it, paste it, scale the copy down a little move it into the original shape and boolean to get my cutout. In 3dsmax, this process occurs exactly as one might expect, with cleanup always being a possibility, but I cant seem to translate this experience into blender, my preferred application now.

I have a picture here somewhere, I'll label the stepper.

https://i.imgflip.com/47d5t8.jpg

I extruded a few sides to make the flanges, and the shape, but its mostly untouched cylinder. I've even done tests, where I make a cube and a cylinder, and if I do any extrusions sometimes it just stops working. Now I'm not talking about a messy cut, I'm talking about no cut at all and random holes in the mesh, cleaning them wont get me the hole, its like its ignoring my boolean and just wrecking stuff. I saw a hint to try solidify, but that did not change the outcome.

I may have to use a tool/addon for this as it is part of my workflow and just makes getting 'holder' shapes so much easier, it seems clear blender has made it not as 'easy mode' as other applications I was familiar with.

edit: I checked out boxcutter and after about 2minutes of looking at the features, bought it. worth $20 to me to have mad boolean powers.

[Neurosys]

Slightly more successful with boxcutter, definitely fun tool, but I cant help but wonder what mysterious secret rule I have violated to make certain shapes fail. I'm happy to triangulate and subdivide or even manual knife them into oblivion, if that will help, but I am used to this occurring as part of the boolean IIRC from 3ds.

https://i.imgflip.com/47d8uz.jpg The left side shows what vanilla blender was giving me, and what I get with boxcutter in non-destructive mode. Destructive mode allows the one on the right, which might be usable with repairs.

I used this to mimic the 'pick a shape' boolean I am accustomed to.
https://boxcutter-manual.readthedocs.io/en/latest/shape_custom/
It worked great until I tried it with the stepper as the shape, but I could use normal cubes to chop the stepper easily.

Would it matter that some of these shapes have been mirrored previously?
Actually now it seems related to extruding a plane. Either way, it now seems easier to manufacture my own cylinders from cubes and knife tool. Thats pretty bad.

Time spent on original design: maybe 15 minutes.

Time spent troubleshooting booleans: around 12 hours, off and on.

Resolution: Start over with additional need to recreate stepper from a different source, then spend x amount of time testing that one for ability to boolean. (workaround)

I'm trying to be constructive with this criticism. If there is some special requirement here, it should be well documented. This works as expected in many applications.

[Ad Hominem]

I'm actually really curious what the heck is going on with those meshes. Have you tried to press M and remove doubles by distance? It looks like either doubles or vertex overshooting each other.

[Ad Hominem]

https://i.imgur.com/FDT5yah.png

It's hard to tell the exact shape but this is what I came up with without using booleans. Is there a cut on the other side of it?

[Blender Release Team]

Co-incident surfaces can mess up boolean operations, just FYI.

[Ad Hominem]

Originally posted by Blender Release Team:

Co-incident surfaces can mess up boolean operations, just FYI.

What does that mean, like hot lining? Or surfaces that exist inside each other?

[Neurosys]

Originally posted by Ad Hominem:

https://i.imgur.com/FDT5yah.png

It's hard to tell the exact shape but this is what I came up with without using booleans. Is there a cut on the other side of it?

Thats the shape I want to inset cut-out. Basically shrink a copy of it down a tiny bit, place it inside the larger mesh, then cut it out, leaving behind a thin shaped shell. It works fine until I try to boolean it. I happened to noticed when I used destructive in boxcutter, the cut made a hole, as in I could see the inside shell, but with a good cut, I get the perfect shell of the subtracted part instead. I have taken to assuming this is due to the initial cylinder being a plane, which I then extruded. This seems to make it impossible to use this shape to 'cut' into any other.

In addition to using it to make a 'holder' for the part, I also wanted to use the same shape to cut into the end of the leg joint where the 'knee' stepper would go (a big cube at the end of a leg). Thats what I was trying to make when this happened. You can see in the images how I changed the leg end from a cube to extruding it to hold the stepper, because I couldnt boolean it for that perfect fit I wanted. (yes, I'm printing these)

I also thought maybe my use of mirror on the objects caused it, just running through everything I did. I used mirror, I extruded cube faces, I didnt do anything too crazy with it. Some of them have also been exported as obj and imported into a new scene, which screws up their 0,0,0 offset, but fixing that manually didnt help either.

I also dont know what co-incident surfaces means in this context.

For background, I've found it is easiest to print/design parts into my models, by modeling the real measurements of the device (like this stepper motor) and then subtracting from the mesh, thats how I got a perfect fit for my rectangular servos. The steppers are cylindrical though, thats when this started.

To test the process I used, try using that stepper 'sizer'(thats what I call them) to boolean a hole shaped like it from a cube or even itself (creating the perfect fitting shell), my own 'sizer' is slightly oversized to make that fit, IF I can get this boolean to work. The alternative is to model these things from measurements, then manually model around them to perfection. I would prefer the boolean obviously.

[The Renderer]

Co-incident means surfaces that are right on top of each other, i.e. they occupy the same space.

So if you want to boolean a hole into something make sure the surface of the cutting object is not flush with the surface of the object you want to cut out of, but make it stick out a little.

[Ad Hominem]

Originally posted by Neurosys420:

Originally posted by Ad Hominem:

https://i.imgur.com/FDT5yah.png

It's hard to tell the exact shape but this is what I came up with without using booleans. Is there a cut on the other side of it?

Thats the shape I want to inset cut-out. Basically shrink a copy of it down a tiny bit, place it inside the larger mesh, then cut it out, leaving behind a thin shaped shell. It works fine until I try to boolean it. I happened to noticed when I used destructive in boxcutter, the cut made a hole, as in I could see the inside shell, but with a good cut, I get the perfect shell of the subtracted part instead. I have taken to assuming this is due to the initial cylinder being a plane, which I then extruded. This seems to make it impossible to use this shape to 'cut' into any other.

In addition to using it to make a 'holder' for the part, I also wanted to use the same shape to cut into the end of the leg joint where the 'knee' stepper would go (a big cube at the end of a leg). Thats what I was trying to make when this happened. You can see in the images how I changed the leg end from a cube to extruding it to hold the stepper, because I couldnt boolean it for that perfect fit I wanted. (yes, I'm printing these)

What about just making the shape then use a solidify modifier to get the shell effect? Then size appropriately for your printing.

[Ben der Baer]

maybe this will help you... https://www.youtube.com/watch?v=WbULqtUIyvw

[Bluebeak]

Personally I prefer to merge objects by deleting faces and matching verts. Booleaning is a really great tool at times but it's sloppy and usually results in more work than it's worth by the end.

[Ad Hominem]

Originally posted by BlueBeak:

Personally I prefer to merge objects by deleting faces and matching verts. Booleaning is a really great tool at times but it's sloppy and usually results in more work than it's worth by the end.

it depends on the shape you're trying to arrive at. Some shapes would just be impossible without booleans