I’ve made a box in Blender 3D that has one side open. This is done by insetting one side then extruding inwards. The normals are all good but when I bring it into UEFN and then make it a blueprint and bring it in the scene, I can’t walk my character into that open box as it seems there is collision on the face that was inset? How do I fix this?
The collision doesn’t work so well with concave, even in complex collision.
Take the collision off your box and attach 5 flat boxes for the collision.
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Good tip. Interestingly it worked amazing the first time I made it, but of course when I went to make a tutorial the collision went all weird… How do you attach 5 flat boxes? I’ll give that a go right now
The best I could figure out is to delete the one that wasn’t made properly and then duplicate the one above it and drag it down. I’m brand new to sorting out custom collision, I couldn’t find a way to just “draw” my own kind of thing
Hi Graeme,
It’s true that simple collision shapes must be convex.
There’s a distinction between ‘simple collision’ (simplified proxy mesh to be used with physics/collision system) and ‘complex collision’ (using the mesh geometry for collision)
I’d start by removing any simple collision that might have been generated on import. (Note my screenshot does not have any green simple collision shapes)
And set the mesh to use ‘complex as simple’
(This box was modeled using the built-in modeling tools)
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Thanks! I removed the collision and set that in the drop down and now UEFN won’t even open that object anymore without crashing… I’ll import a new object and try again.
Ok, I reimported the 3D object (fbx file) and took off the collision, set the dropdown, showed the simple and complex collision, saved and it worked a treat. Thanks.
I have learned something new today.
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@Astrotronic thanks for rescuing poster from my nooby tips and teaching us all again 
I did have some issues from a spawn bunker, a hollow shape with a few openings that was not colliding as wanted. I remember redoing it in convex pieces,
however in cases where complex collision is not working as needed, is it feasable to construct simple geometry with UEFN modelling tools, attaching them as a child to fancy mesh and setting them as Hidden in Game with an invisible wall preset to use as the collision ?
@GraemeBB this is where I was going, making the box shape with modelling tool boxes to represent the wall collisions, lucky Astrotronic collided with the thread, so much simpler.
Glad to help. The problem with creating extra meshes for collision is that you then need to manage them. (It could get messy)
A static mesh placed in the world with ‘Hidden in Game’ would work though. (I’m not sure about the specific differences between ‘BlockAll’ and ‘InvisibleWall’ collision channels)
Another approach: multiple meshes that make up a structure with the same origin/transform. So you could have a collection of meshes at the same XYZ location (Same rotation and scale as well) and they’d be offset appropriately + seamlessly fit together.
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I have a bunch of invisible static meshes in my map so that bots can navigate over static meshes, and I just put them in a ‘blocking volume’ subfolder so that I can make them visible/invisible easily.
That’s an interesting way to do it, I’ll have to give that a try
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