how do i cut a hole in a mesh?

I want to cut a hole out of a mesh. For example, I want to be able to create a shape that I want the hole to be, and then cut that shape out of another shape.

I don’t know if this is making any sense??

Hi roo,

What you’re trying to do is called boolean operation.

You can get information from the blender 2.3 user guide on boolean operation at this address:

http://www.blender.org/modules/documentation/htmlI/x2389.html

Good luck,

Boiwei

this looks good but it would wreck a mesh using subsurfs becouse of all the tris

Blender’s boolean operations are less than perfect. less than average, I’d say. If you REALLY want to use them, I find that subdividing the two operand meshes a couple times gives better results. Other option would be to use the Knife tool to cut the hole, but this is a little trickier, and again, it works better with denser meshes. Might be best to have an image of the hole you want to cut as a background image, then trace around the hole, if your hand is as bad as mine! :wink:
This kind of operation is done best with CSG (Constructive Solid Geometry). Povray is a renderer with good CSG support. I don’t know much about the internals of blender or the way it renders… is anyone who’s familiar with the code know if it would be possible that someday blender could support CSG trees or something?

Anything is possible with Blender but what’s important to recognize here is that the current tool set is more than sufficient to produce ANY DESIRED MESH. With some time and effort you can produce anything quickly and relatively pain free. Yes thats right, pain free. One great thing about this piece of software is that it gives you a new way of visualizing the creation of an object. A mesh gives you great advantage over real life. In real life you start with a solid block of material and you cut out of it because in real life you HAVE to start with a solid block of material. In Blender you can build from scratch as long as you know how to use the tools. If you think ahead a little, adding holes in a mesh is just part of the process. Using CTRL R and the X key you build a hole any shape you want. It just takes some patience.

The reason I’m saying all of this is that a lot of users who arrive on the Blender scene are used to having good boolean support in other applications and when they find that they’re missing they assume they can’t create much of anything with Blender instead of realizing there’s just a different approach to modeling with this piece of software than with some others.

To put not to fine a point on it: Booleans in Blender suck. They’re essentially an experimental toy and haven’t been developed at all in comparison with the mesh editing tools. Don’t waste your time with them. Find another way. Once you HAVE another way, booleans might come in handy now in then, but don’t expect them to be a reliable or useful tool for modeling with this particular piece of software. In my opinion it isn’t worth the fuss.

Take a look at the scripts forum. There is a current project bieng done by SpkyElectrc to rewrite the boolean tools of Blender. All the unwanted extra vertices and faces which the current tool generates will not be there anymore. The image shows the results with the new and the old boolean tools respectively:

http://img83.exs.cx/img83/2699/bool.jpg

As you can see, all faces that have nothing to do with face to edge collisions will remain totally unaffected and a very simple but effective face filler will ensure that convex quad polygons are always used before any triangles, thus keeping polygon count as low as possible. I must say this filler is a very smart piece, because it is my own idea and invention, to see a diagram of how this works visit this thread:
http://www.elysiun.com/forum/viewtopic.php?t=29200

It will also subdivide your UV polygons and average your vertex colors so all textures will be kept, so you will no more feel other software has better boolean tools.

You can even try the python script which already shows its great potential.

Just wanted to say a quick thanks to everyone for this info - I thought I was being a bit of a dumbas* but I think its just a case of getting more experienced with creating meshes…

I will persevere and check out some of the links you posted.

cheers guys - drinks are on me

You can also do it manually, put the hole polys in an empty place in the mesh then make faces to connect it. It’s much cleaner then booleens and saves you mesh cleaning.

As a new user who bought the user guide and wants to put shaped holes in meshes what does that mean?

What is a hole poly and how do I “make faces”? A face, I am assuming, is the surface between vertices.

TIA

What is “the empty place” besides the one in my head? :o

he may mean this (an example).

you delete the face that needs to have a hole in it. then you manually add a circle for example, and connect each vertex of the circle with the corresponding vertex surrounding triangle or quad.

note: the new bools are very clean + they do nothing diffrent than this. so why do this? I must have misunderstood you Kansas_15, since this would be nonesense :slight_smile:

What is a hole poly and how do I “make faces”?[quote]

If you want to quickly make faces and edges just select “the empty places”
and press shift f and it will add faces but they gett all messed up when you try to smooth and/or sub divide it, if that is in fact what you are asking.