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All Collisions Not Showing

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    All Collisions Not Showing

    I have a model I am trying to get in UDK. I have made the collision mesh out of the original model and adding optimizations to get it to a lower poly count. I have named my collision mesh UCX_Name but as you can see in the screen-shot not all the collisions show up.

    Hi there!

    I totally understand your frustration. I was dealing with collision this past week, but I've finally gotten my answer (thank you to the UDK forums and those who partake)!

    For starters:

    The model looks pretty good! Which 3-D package did you use to model it? I personally use Maya 2009, so I don't know how much I can help you with this, but I'll give it a shot!

    Tip #1:

    It isn't the best to create a duplicate of your mesh and try to optimize it. The reason I won't advise this is because of how picky the Unreal Engine is when it comes to importing your own collision model.

    As described in the Collision Reference in the UDK Documentation, you have three naming conventions that determine what your collision type will be inside UE.

    UBX_= Cubes, squares, or perfectly aligned rectangles.
    USP_= Sphere shape primitives
    UCX_= shapes that must be CONVEX, NOT concave! Refer to the document for a sample image.

    So, I believe the first problem (based on what you have provided) is that you've made a duplicate mesh of your castle, which consists of multiple concave (or non-convex) shapes. This is NOT accepted and will not be imported into Unreal. You need to split your collision model into pieces in order to maintain either a Cube, Spherical, or Convex shape.

    Read into this thread (the one I posted several days ago). This shows you my trials and errors with collision pieces. Farther into the thread, I show a picture of my door (which is non-convex) and its collision model (split into 3 pieces). Hopefully that will give a visual of what I'm trying to explain.

    Here's the link:

    It does take more time AND the Documents suggest that you keep your collision primitives under the count of 10. So try to use the smallest amount of collision primitives possible, especially with something as complex as a castle model. I would also suggest that you optimize your castle mesh, building separate pieces with simpler collision. This will help Unreal process everything faster since it isn't processing ONE single mesh.

    EDIT: To give us more guidance on your situation, list out the process of your exporting the mesh and collision model and the options you've checked upon importing. There are specific options that could make or break this process; results are based upon my previously mentioned trials.

    Try it out and let us know what happens.

    ANYONE ELSE, please feel free to correct me, I'm only going off of my own experiences within this last week.

    Good luck foodstamp!


      The model is actually a part of the Mid East pack from Arteria 3d

      I used 3ds Max student version to get the model in and add collision

      I followed this tutorial here on You Tube except the part about the boxes. I will put the boxes around right now

      Since I have some buildings that have interiors how would go about doing the collision on them, as I have not seen any tutorials for that type of model. They all either use solids or exterior meshes only


        Oh, ok. Yea, so in 3DS Max, I don't believe it's much different from Maya (when importing collision models).

        You are using ActorX, correct?

        In order to obtain collision for the inside of the castle, you must create multiple convex primitives or rectangles (depending on the shape of the model) and place them over each wall, roof, floor, etc. You can't necessarily use ONE collision model for this. If you were to replicate the inside geometry and use that as its collision model, it would not enter because of the convex rule.

        So again, in order to bypass this, cover the walls, roof, and floor with their own collision pieces. I'll set up a quick example in Maya and visually explain it tomorrow. I'm a bit busy today.

        MAKE SURE all your collision models have CLOSE faces! Don't forget that!

        Good luck!


          I am actually using ASE export. Does it matter with static meshes?

          And just to be clear, I have the 1 year membership to Arteria before anyone goes asking how I got these models

          I have the Shanty Town pack and it has a lot, I mean a lot of complex models. Buildings with poles and such. That means I have to make a collision for each and every place that I want something to collide?


            ASE works fine with static mesh.
            Yes. You'll get a lot of practice at making primitives in Max.
            Although, with anything simple like flag poles, you can usually let UDK make your collisions for you in the mesh properties. It just doesn't work very well with complex shapes like your building.


              You've got some choices here...

              1. Break your model into pieces for "building blocks". Then you can add collisions to each piece and assemble them inside the editor to form the final building. This is the preferred method to build things in UE3. It's the most efficient method for the engine but the most work from your side considering the models are already built and you need to rebuild them... to a certain degree. You also won't have problems with light maps.

              2. Keep the models as is and build custom collisions inside Max. This is still lots of work for you, building collisions, less efficient in the engine as far as the model goes, probably kiss light maps goodbye, but should be efficient for collisions.

              3. Use the model as is and force per poly collisions. This means no work for you but again no light maps but collisions should work.. in theory.. (don't know what the engine will do on such heavy loaded collisions). So you will have some seriously inefficient models and collisions. This is not recommended.

              You really should just go in and create some building pieces based on the existing model. That's of course if you wanna use this for game play, which I assume you do if you care about collisions.


                I see that you have collision model around that door frame. Does your character need to collide with the contour of that door frame? Will he climb on top of that dome? Think about where your character needs to collide and make it simpler. I don't think your collision needs to be any more than a few boxes.