topic Re: Help with Difficult Boolean in 3ds Max Modeling Forum

Help with Difficult Boolean

trinitifx — Mon, 22 Apr 2019 22:58:43 GMT

I have a model I created of a cap badge, similar to this:

https://www.atlantakilts.com/store/scottish-crest-cap-badge.html

I printed it out with my 3D printer and it came out great!

I got some high-heat resin and want to print out a mold of the badge to make a pewter version.

I can't seem to get a good Boolean subtraction of the badge on a box to make a mold.

All of the parts are separate meshes, I'm not sure if that is the problem or not.

Can someone else look at it?

Thanks!

Re: Help with Difficult Boolean

leeminardi — Tue, 23 Apr 2019 02:15:25 GMT

It looks like "Hub City..." has already been subtracted from Box001 and HCH Box is easily subtracted from Box001. What specific object can you not subtract from what other object?

Re: Help with Difficult Boolean

trinitifx — Tue, 23 Apr 2019 02:23:18 GMT

I figured it out-

or actually, I sent it to Netfabb and had them do the Boolean.

Perfect!

Re: Help with Difficult Boolean

trinitifx — Wed, 24 Apr 2019 12:22:25 GMT

Ok, I spoke too soon..

Please check the attached. I've had to extrude several parts to make sure they completely cut from the MOLD (blue box)..

All parts should be subtracted from the MOLD (blue box).

If you select the MOLD (blue box) and add a pro Boolean modifier, you can subtract the STRAP and it works fine. If you next select the purple HCH TEXT in the middle, everything disappears. If you reverse this order, the same thing happens.

I've checked all the subtraction models with the STL Check modifier, they all pass.

How to get this Boolean to succeed?

Re: Help with Difficult Boolean

ads_czechoj — Wed, 24 Apr 2019 12:59:35 GMT

At one point of creating the Boolean (I am using the Boolean instead of the ProBoolean), geometry disappears.

Please look at my attached gif. Is your issue with the ProBoolean similar?

Re: Help with Difficult Boolean

leeminardi — Wed, 24 Apr 2019 14:12:04 GMT

I think the problem lies with the object HCH BOX. I deleted the side faces of HTH BOX and then recreated the polygons for the sides of one of the H's as an experiment. In creating the new side polygons I was careful to specify the vertices in a CCW direction to ensure that their normals would point outward (not sure if this was necessary by it doesn't hurt). I was then able to successfully use ProBoolean to subtract the new "H" from the object that was the result of subtracting STRAP from MOLD.

I suggest you rebuild the side polygons of all the geometry of HCH BOX.

Re: Help with Difficult Boolean

trinitifx — Wed, 24 Apr 2019 14:41:41 GMT

I get a similar problem (see attached)

Re: Help with Difficult Boolean

trinitifx — Wed, 24 Apr 2019 14:48:09 GMT

Thanks! I will check on that..:)

How could this have passed the STL check if there are problems with the mesh?

Strangely, it probooleans fine if you select it first (see attached)

Re: Help with Difficult Boolean

leeminardi — Wed, 24 Apr 2019 15:01:34 GMT

I recreated the walls of the "C" and it subtracts fine.

Re: Help with Difficult Boolean

trinitifx — Wed, 24 Apr 2019 15:14:46 GMT

Thanks!

I used XView and it shows I have flipped and overlapping UVW faces on the HCH Box (obviously)

Is the easiest way to fix that just to re-create the faces?

Selecting the polygon and flipping doesn't seem to do anything

Re: Help with Difficult Boolean

leeminardi — Wed, 24 Apr 2019 15:43:27 GMT

"Is the easiest way to fix that just to re-create the faces?"

I think so. It should only take a few minutes to create new polys. Keep the top and bottom polygons and create new side polygons.

Re: Help with Difficult Boolean

trinitifx — Wed, 24 Apr 2019 15:47:09 GMT

Ok, thanks guys for looking at that!

Using XView, I checked some of the other meshes and it looks like I've got some work to do.. Arg!

Re: Help with Difficult Boolean

ads_czechoj — Wed, 24 Apr 2019 16:33:42 GMT

At least one of the objects being used in the Boolean operation has some interpenetrating parts, which confuses any Boolean computation you might try.

The object in your model which causes the problem is the "Strap OVER HANG" (on attached image).Solution to the problem: Consider to rebuild the "Strap OVER HANG" object.

There is few places on internet where you can find the answer to the question: "Why are self-intersecting polygons bad?"

One of the explanations:

If the line crosses over itself to form a loop, then the left and right polygons get reversed for the portion within the loop. The list still shows polygon 1 being on the left and polygon 2 being on the right, even though that is not the case within the loop.

Thus if you try to fill a polygon or determine its neighboring polygon, the algorithm gets confused when a loop is present, and it will fill or indicate the wrong polygon

Re: Help with Difficult Boolean

trinitifx — Wed, 24 Apr 2019 20:05:34 GMT

Thanks for that

It looks like the root of all my problems is poor modeling.. 😞

arg