topic Re: ShapeBoolean accuracy issue in 3ds Max Forum

ShapeBoolean accuracy issue

wimmer_simon — Thu, 14 Aug 2025 19:35:59 GMT

When creating a ShapeBoolean, the result is not as accurate as it should be.

When zooming in there is a little difference between the original shape and the result in the boolean.

Create two lowpoly shapes.

Use the first to create a ShapeBoolean.

Create an instance of the second shape.

Subtract the second shape inside the boolean.

Zoom in end check the result of the instanced shape and the result in the boolean. They will be slightly different.

Re: ShapeBoolean accuracy issue

MartinBeh — Fri, 15 Aug 2025 07:38:44 GMT

It would help if you could upload a .max file with some test shapes?

Re: ShapeBoolean accuracy issue

wimmer_simon — Fri, 15 Aug 2025 08:39:33 GMT

Attached is a max file.

The red shape is the result of the ShapeBoolean. The yellow shape is an instance of the subtracted object.

When you zoom in, you will see a slighty difference between the red and yellow lines.

Re: ShapeBoolean accuracy issue

MartinBeh — Fri, 15 Aug 2025 10:23:45 GMT

Thanks for the scene file - I can reproduce what you describe.

There seems to be some (small) differences in how the shapes are calculated by "native" 3ds Max and by the ShapeBoolean code... For the triangular case on the left, I measure a gap of 0.004 units between the ShapeBoolean result and the original subtraction shape. This is small but not nothing.

There also is some noticeable difference in the resulting shape and the operands if you check the box at Display > Operands in the ShapeBoolean.

Not sure what is going on.

Re: ShapeBoolean accuracy issue

MartinBeh — Fri, 15 Aug 2025 11:05:53 GMT

FYI, I submitted a bug report for this - but no idea when/if this will be fixed...

Re: ShapeBoolean accuracy issue

wimmer_simon — Fri, 15 Aug 2025 11:56:19 GMT

thanks.