Blender booleans

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blendermax
Posts: 42
Joined: Sun Jan 19, 2003 8:30 pm

Blender booleans

Postby blendermax » Sat Nov 01, 2003 6:44 pm

Everybody knows blender needs new booleans. With the current toolbox, I believe it's possible to create booleans using code from the knife tool (when it will support subdividing faces), and of course some supplemental code (not that much I think). The idea is as follows:

1. Two objects, that intersect eachother are present in a scene.
2. The operation is selected from a menu : Unify (A+B), Subtract (A-B), Intersect (A*B), Inverse Intersect (A/B)
3. The points (as in points in space) where the two meshes intersect (knife tool code), are created on the surface of the objects, and the two meshes are joined (whatever code responds to shift-j). Finally, doubles are removed in order to properly join the meshes. Now we have a combination of the two objects.
4. Depending on the operation, some points belonging to the mesh(es) are deleted, and faces are created wherever appropriate, ie. to cover up holes (haven't come up with an idea for this yet).

examples of this can be seen here - with the exception of Inverse Intersect; forgot to do that one, and can't be bothered now (just imagine what is left of the two meshes after the product is subtracted from both of them - it will look like A+B, with the sole difference that two objects will be left at the end):

Image
A+B

Image
A-B

Image
A*B

Is this feasible?

blendermax
Posts: 42
Joined: Sun Jan 19, 2003 8:30 pm

Postby blendermax » Sun Nov 02, 2003 7:36 pm

40 views and not a single response? no wonder this forum's dead. i need feedback!!! :shock:

theeth
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Location: Montreal
Contact:

Postby theeth » Sun Nov 02, 2003 8:02 pm

Patience is a virtue

Martin
Life is what happens to you when you're busy making other plans.
- John Lennon

Money_YaY!
Posts: 876
Joined: Wed Oct 23, 2002 2:47 pm

Postby Money_YaY! » Sun Nov 02, 2003 8:03 pm

41

not enough coders. not enough time, not enough care, not enough team work

take your pick ..

Carnivore
Posts: 55
Joined: Thu Jan 30, 2003 6:27 pm

Postby Carnivore » Sun Nov 02, 2003 8:15 pm

Money_YaY! wrote:not enough coders. not enough time, not enough care, not enough team work

I'd say not enough time and/or coders. And god, I hope I'm right :roll:

theeth wrote:Patience is a virtue

What exactly are you saying? :)

stiv
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Joined: Tue Aug 05, 2003 7:58 am
Location: 45N 86W

Postby stiv » Sun Nov 02, 2003 9:18 pm

blendermax wrote: i need feedback!!!


You also need better handwriting. You know blender has text, right?

theeth
Posts: 1184
Joined: Wed Oct 16, 2002 5:47 am
Location: Montreal
Contact:

Postby theeth » Sun Nov 02, 2003 9:48 pm

Money_YaY! wrote:not enough team work

I think you should stop shooting random absurdities.

Martin
Life is what happens to you when you're busy making other plans.

- John Lennon

blendermax
Posts: 42
Joined: Sun Jan 19, 2003 8:30 pm

Postby blendermax » Mon Nov 03, 2003 10:08 am

stiv wrote:
blendermax wrote: i need feedback!!!


You also need better handwriting. You know blender has text, right?


i know blender has text, but your comment is hardly relevant I'm afraid...

as for the others, what i meant by feedback was not telling me how it cannot be accomplished, but if this idea is any good in itself... thanks for the input anyhow.

stiv
Posts: 3646
Joined: Tue Aug 05, 2003 7:58 am
Location: 45N 86W

Postby stiv » Mon Nov 03, 2003 9:20 pm

blendermax wrote:i know blender has text, but your comment is hardly relevant I'm afraid...

Sorry if I seemed flippant. It wasn't mean as a personal attack. I'll be more explicit.

You wanted feedback. If the red scrawls on the overly large images are relevant to the point you are making, then it is in your own self interest to make sure they are understandable. If they are not relevant, then they are just noise on the channel and are unnecessary.

Blender has a Text type that is useful for annotating images. I was unable to decrypt what you had written. I say this as someone who has insanely bad handwriting.

There are some interesting historical reasons for the current state of blender boolean operations. However, since the site here is running so slowly, we'll save that post for another day.

LoZaR
Posts: 4
Joined: Fri Oct 18, 2002 11:17 am

Postby LoZaR » Mon Nov 24, 2003 10:55 am

Hi blendermax,

This is an interesting idea, I think for convex objects with a single plane of incidence it could work well. In order to extend your algorithm to more complex shapes you will need to provide more detail on how exactly you compute the cut path - this is not clear to me from your drawings.

Basically all boolean operations on models have two steps,

Partition each mesh with respect to the other.
- Find the cut path
- Do the cut

Workout which parts of the object are inside/outside the other object (which for complex shapes is not trivial)

You have a tool to 'Do the Cut' but we will need more details on how you intend to deal with other parts of the algorithm.

Now so far so good, but if you really want people to implement this you must also proove that this approach is useful as a modelling tool and not just something that's easy to do.

Modelling imposes some extra requirements on a boolean algorithm:

1) Should produce a miniumum number of polygons (so no soup of polygons a la current BSP based algorithm)

2) Should not produce T-junctions in the output mesh. Or at least it should be an option. (Inevitably no T-junctions means higher polygon count)

3) Should deal with vertex/ face properties perfectly (presumably the knife tool does this already right?)

4) Should try and produce good quality polygons (no long thin uns) [difficult]

Look at the requirements for a new tool before implementing is essential. I learned this the hard way after coding the current booleans for blender without first considering what the artists wanted (I was more interested in coding a BSP implementation - NERD) - a lot of waisted development effort with a poor result.

Of course feel free to experiment yourself but if you seriously wish to propose an algorithm for others to consider it should be well worked out and well presented. You might also consider comparing your ideas with existing algorithms. Maybe spend a while googling and reading up on the subject - looking at what others have done means that you wont miss any part of the algorithm and it's also good for stealing a few ideas!

Cheers and good luck,
Laurence.

levon
Posts: 415
Joined: Thu Jul 31, 2003 6:06 am
Location: adelaide

Postby levon » Mon Nov 24, 2003 4:28 pm

i think one problem you might run into is that you can only cut each edge once with the knife tool

blendermax
Posts: 42
Joined: Sun Jan 19, 2003 8:30 pm

Postby blendermax » Tue Nov 25, 2003 3:55 pm

actually i've pretty much dropped the idea until further notice. dont have the time and i dont have the patience either (figuring it out and dealing with your complaints about my ever-so beautiful handwriting :roll: ).

alltaken
Posts: 127
Joined: Mon Oct 14, 2002 7:08 am

Postby alltaken » Wed Nov 26, 2003 11:47 am

hey blendermax i have also been wanting this to be true.


i want a feature of booleans that will ONLY cut the face at the intersection between an edge and a face.

i have also been looking into a block building method that is later built by the computer into a mesh.

Image

Image

Image



yeah i have been very very frustrated with boolens, i really want the intersect button back as well as boolens as IMO it worked better for my jobs.

but its always hand fixing of mesh's anyway.

(whips out maya, arrrgggghhh :P J/K)


alltaken


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