BSP Brush Cutouts

[Crash_Override]

Lets say I have a wall 256 high 512 long and 16 thick and I want to use my build-a-brush to cut out a window, I adjust it to the size I want and place it in the existing wall. What do I do to cut out the window (not add a subtractive brush) but just cut it out and leave the window piece there so I can apply one material to the wall and a different one to the window.

[Sneaky_Ferret]

Sorry if I misunderstood what your asking. But as far as I know its perfectly fine to overlap additive solids and you wont get any issue. Such as what I did here. Simply move your builder brush inside your solid anywhere you want and add it again.


If I misunderstood you then feel free to correct me on what you meant.

[Crash_Override]

Sorry if I misunderstood what your asking. But as far as I know its perfectly fine to overlap additive solids and you wont get any issue. Such as what I did here. Simply move your builder brush inside your solid anywhere you want and add it again.


If I misunderstood you then feel free to correct me on what you meant.

Ok, see where your red brush builder is, I just want to cut the shape out but leave the chunk there, like its 2 separate pieces. If I add geometry within other geometry that have faces on the same plane, like they way you are doing it, when you apply material to the wall and then the window, in game it will glitch back and forth.

[JessieG]

You would be better off making a mesh to use there for a window instead. Just make it match the dimensions of the cut out when using a subtractive brush and place the mesh there.

[1/2Hawk]

BSP works quite a bit differently than modelling something in Max, Maya, Blender etc... where you could for example, snag a few polys with a tool and break it off into a totally separate mesh to manage on its own. Best analogy I can give is to think of everything you made in the scene that is BSP is one giant Boolean object, and every BSP *brush* you placed is either an additive or subtractive operation stored in a specific sequence of steps.

This is why you have to do what you're asking in two steps - one to cut out a hole where the window would go, and another to add back the window. Fortunately, that can be done without changing the size or position of the builder brush. Be careful when changing the order of operations later on though ... you dont want to cut a hole out of a wall that hasnt been created in the stack yet, you dont want to cut a hole after the window was added or it will cut thru both, you dont want to make the wall last, etc etc.

Hopefully that explains why you cant cut something out and leave a piece behind. But you can get creative with the builder brush though to accomplish the same idea. For example, you *could* start with an 8 sided cylinder and (using the snaps) squash two opposite sides into a rectangle wall, and take those same lower verts up and higher verts down... voila, a flat wall with a inset window. You *could* also grab opposite sides of the builder brush in a top view (edges, not surfaces) and click on Split in the Geometry Tools popup to create additional edge loops that can be moved around to get what you want. Lots of ways to skin that cat.

[White Paper Games]

Nice reply there Hawk!

[FelixofMars]

Yep, using it is like using a boolean subtract in a 3D editor, I am going to say that BSP is becoming more and more redundant in unreal and I expect it will go completely one day. You are better off doing it as a mesh. I do like BSP in some ways but in other ways its not particularly useful and should be limited to quick prototypes and even then its still easier to create and export from sketchup for example.