extra edges created when using boolean difference

Support Modeling
1

hi guys, very new to blender here so im sure this has been answered before, but i cant find an answer.
i have made a cube with a slightly smaller cube but out of it using boolean difference, which worked fine.
but when i cut hole in the “hollow box” i end up with 2 edges being created on both the inside and the outside which cant be deleted or dissolved. is there any way to fix this?
blender file is attached.
thanks
house.blend (411 KB)

1 Like
2

to clarify, if you go in to edit mode and look from the outside where you can see the hole, there are two unnecessary edges on each side going diagonally.
i dont mind them being there of course, but i feel like they might cause problems later down the line when it comes to texturing

3

Blender doesn’t support faces with holes in them without any connecting edges. The edges are necessary to support the geometry to make the hole. The two faces have more than 4 sides so those are n-gons and if anything, those should have more connecting edges to make them convex.

Jumping to boolean operations and removing “unnecessary” geometry are a common reason beginners run into trouble with polygonal modeling. The structure is important

4

thanks for the reply.
ah i see, no holes allowed. so if i add edges in a place that works better for me then i should be able to dissolve those ones? i will try

i am starting to get the impression that boolean operations are not the best way to do things unless necessary.

5

i added a new edge from each corner of the hole to each closest corner of the box, inside and out and i still cant dissolve the edge that i no longer want. does this edge have to stay because it was forcefully created?

6

here is the project now. you can easily see which edge i want to get rid of.
i do notice, however, that my new edges show in wireframe mode, but the ones that were automatically created do not. why is this?

house.blend (411 KB)

7

ok so it seems that i can simply delete the edges, then create a new face, but i must be doing something wrong because i dont really understand the behavior.
i have also noticed that when i select a face, the selection seems to ignore my new edges. i created them by selecting two vertices then using the “make edge/face” button.

sorry for the multipost :confused:

8

That’s a valuable insight. In polygonal modeling software I always tend to think of Booleans as a last resort, as they notoriously create messy geometry that needs thorough cleanup afterwards.

9

i see. i will try to avoid using it. thanks

10

That would be why. Creating edges on top of existing faces doesn’t split the faces, just puts a new edge on top. Vertex connect path (J) or knife (K) should be used instead.

Edit: these go through many useful tools but would suggest watching all of them
https://www.youtube.com/playlist?list=PL0AfIdK08E7_PKsXOO_yuAql9b3hdcwPR

11

thanks! i will go through those videos. i have so many videos and tutorials to go through. i start on a couple then get carried away playing around :slight_smile:

thank you for your patience with my noob questions.