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    bsp mesh holes

    Ok, this is a constant problem I've had with Unreal 3 and also a problem I've seen a few other users complaining about.

    Occasionally UnrealEd will decide to completely screw up the build process of bsp meshes and remove polys that shouldn't be removed. This happens mostly, I've discovered, while using subtraction brushes in combination with additive brushes. It also happens in both subtractive and additive worlds.

    It seems like UnrealEd is cutting the mesh in unneeded places and then removing polys. I tried messing with the brush order, as that seemed to be a common suggestion on other posts, but this didn't do much.

    Occasionally I've copied all the contents in to a new file and rebuilt all, and it's fixed the problem, however that doesn't always work. Sometimes I've deleted the problematic bsp and recreated, that also sometimes works and sometimes does not. Sometimes I create a new bsp and it fixes the problem but gives me a bsp hole somewhere else! Everything is aligned and snapped to the grid properly so there can't be any problem in that respect.


    You can see from the pics below, some of the problems, the mesh view shows the mesh cut in places where it doesn't need to be cut and then removing a poly.






    #2
    In my experience you get this sort of problem from too many shapes overlapping/intersecting or just meeting at weird angles. In the last screenshot it looks like your walls, floors and ceilings are aligned in an unusual way and a little more complicated than they should be - maybe try moving them so that the top faces of the walls align with the top faces with the ceilings and so on, instead of only their corners touching.

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      #3
      Hey Setheran,

      Thanks for the tips Though unfortunately they didn't work, plus the bsp setup is not at a weird angle, (it may just look like that from the angle of the screenshot), it is simply a setup of boxes that are all snapped to the grid.

      Also the thickness of the walls are all 32 units in case anyone was wondering, as I've heard that brushes that are closer than 32 units can sometimes cause these errors.

      I also tried building a simple brush in a completely empty space away from the level and this i what I got:



      As you can see the builder brush should have created a standard cube poly with 6 sides and 12 triangles but it's cut it unnecessarily.

      Does anyone know if this is going to be fixed in a future patch? Because it's really slowing down any progress I can make with the level

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        #4
        I got the same problem.

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          #5
          How have you done the room? Best way would be to place one additive cube and then place one subtractive cube in it. No need to have seperate BSP meshes for the floor, walls and ceiling.

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            #6
            Originally posted by el_simmo View Post
            I also tried building a simple brush in a completely empty space away from the level and this i what I got:

            As you can see the builder brush should have created a standard cube poly with 6 sides and 12 triangles but it's cut it unnecessarily.

            Does anyone know if this is going to be fixed in a future patch? Because it's really slowing down any progress I can make with the level
            What is size of that brush? And can you give us download to your BSP (uncooked, so it is smaller). then we could rebuild it on our computers and compare BSP cuts. Just be sure to build all and zip it immediately, so we get exactly same file as you have. Also what is exact model of CPU and motherboard in your computer.

            There is something fishy going on with UT3, I for instance have lots of trouble with bots, they just love to bounce between 2 random nodes. But nobody usually complains about it on my released maps. We need to trace those bugs, so Epic can fix them.

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              #7
              And by looking on your brushes , you are doing construction a bit wrong.

              Even in additive level do not make separate brushes for each wall. Make one big brush to contain your level or part of it, then rooms carve from it. After you have basic construction layout (huge brush with carved rooms inside), add smaller detail like ramps, pillars door frames.

              This way you have structure like: Huge additive brush > medium sized substractive for roome > and small (that are contained in single rooms) detail brushes.

              It makes easier for engine to render, because it uses binary trees to remember priority and order of rendering for BSP. I am guessing here but engine most probably have trouble with many overlaping brushes.

              PS. And best tutorial to see BSP work is opening old UT99 maps, back then BSP was mastered.

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                #8
                Thanks for the tips guys, Nawrot that brush is 256 x 256 x 32. I haven't tried using a huge additive brush with a subtraction inside it yet, but wouldn't that make additive worlds completely pointless?

                My CPU is an AMD 3800+, and my motherboard is a rubbish old MSI AGP board, (yeah I know, I need to upgrade :P) I can't quite remember the model number but I'm at work and want to get this post out quick. It also gives me the same error on my laptop, (a dual core Pentium CPU with a ATI x1300) and on my machine at work, an Athlon 64 X2 5200+ with an 8800 GTS on an ASUS M2n SLI deluxe.

                Anyway, there's a link to the map file here

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                  #9
                  Typically you will get strange cuts or bsp holes when...

                  1. There is some complicated brushes in the world (many vertices on one brush)
                  2. Slicing a bsp at odd angles
                  3. BSP overlaping others uncessarily and or not aligned to grid
                  4. Performing a de-intersect or intersect on several brushes to make one complex brush
                  5. Rotating brushes on an angle. (Usually because part of the brush wont align with the grid)
                  6. Moving individual vertices of a brush
                  7. Attempting to merge poly's on a complicated brush

                  Basically anything that would be difficult or complicated for the engine to deal with will increase the chances for holes and strange cuts.

                  As far as your setup goes though, unless you have other bsp in this map, i really am not sure why its happneing. Also regarding Additive and Subtractive, there is a time to use one or the other depending on if you want it to be an inside or outside map. Plus some just find it easier to work with one method versus another. Just depends on personal preferance.

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                    #10
                    Most of the time you can fix bsp holes by duplicating the brush, for instance you have a brush with holes, move it out of the way on an axis, then alt drag a new copy of the brush back in to the position you need it, remember brushes stack, so if you have a brush that intersected the first brush, say a subtractive on an additive, you will have to do the same with the subtractive afterwards to get the effect you previously had.

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                      #11
                      Holes have been present since UED1.0, but they are much less frequent nowadays. You just need to learn how to build things in the correct way to avoid holes. When a hole does crop up you can usually build the shape in a slightly different method and have success.

                      Looks a little strange that you were having holes in such simple geometry. I do waaaay more complex curves and angles with little problem. Any remotely square is always clean.

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                        #12
                        Typically you will get strange cuts or bsp holes when...

                        1. There is some complicated brushes in the world (many vertices on one brush)
                        2. Slicing a bsp at odd angles
                        3. BSP overlaping others uncessarily and or not aligned to grid
                        4. Performing a de-intersect or intersect on several brushes to make one complex brush
                        5. Rotating brushes on an angle. (Usually because part of the brush wont align with the grid)
                        6. Moving individual vertices of a brush
                        7. Attempting to merge poly's on a complicated brush
                        I agree, had the same problems with my one map, only because of strange angels and the cutting of my brush, which I then have to rebuild. I found it helps to rebuild all the brushes around the problem one by one until the problem is found, starting with the unusual shapes 1st. It usually solved my problems

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                          #13
                          When I built Phobetor I ran into a bunch of bsp holes because of the way a lot of the brushes are cut and shaped. The latest map I've been working on has a ton more bsp in it and I've finally figured out how to get rid of bsp holes once and for all.

                          When you see a bsp hole you should select the bsp brush it's showing up in, click the brush/polygon/vertex (or whatever it is) editing tool (it's the button to the right of the camera mode), and then switch it into polygon editing mode. What you're going to find is that the engine has for some reason missed a couple of vertices or joined them in the wrong order. What you can do is start deleting faces of the polygon. Then use the vertex editing tools to create new faces using the proper order of polygons. Once you've replaced the faces that have the bsp hole then you'll need to rebuild to see the changes.

                          It's a rather complicated thing to explain in text, but the polygon editing tool works wonders for getting rid of bsp holes. I've done some wildly complex brushes and haven't had issued with bsp holes anymore since I learned of this. Bsp holes used to be an issue in older versions of the editor, but not anymore!

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                            #14
                            there u go, something like what I said.

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