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UE3 - UT3 Getting stuck on smooth surfaces

Discussion in 'Mapping' started by guitarxe, Dec 29, 2010.

  1. guitarxe

    guitarxe New Member

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    I've got an angled corridor, and when I test the map in editor and I walk by it and hug it, I'm getting snagged on it for some reason. It's a perfectly smooth brush, simply angled a bit. What could be causing it?

    Here's a screen of the brush in the editor:
    [SCREENSHOT]http://img.photobucket.com/albums/v376/guitar_xe/snaggingonwall.jpg[/SCREENSHOT]
     
  2. Bi()ha2arD

    Bi()ha2arD Toxic!

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    I had this before. My guess is the engine is being an asshole. The way I fixed it back then was put a blocking volume around the wall. No idea if there is a better solution to this.
     
  3. guitarxe

    guitarxe New Member

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    Blocking volumes. They always seem to save the day, eh?

    But now I'm gonna have to go and lick all the walls in my level to make sure there aren't any more snags =(

    Thanks for the help!
     
  4. Odedge

    Odedge Keeper of Tutorials

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    In my experience, BSP walls won't snag the player. How far do you have to walk away from the wall until the player can continue walking forward?

    I am thinking you have 2 BSP faces that aren't aligned or there is a BSP error causing the invisible "wall", which is snagging the player.
     
  5. guitarxe

    guitarxe New Member

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    This seems to be happening to all my surfaces that aren't straight. And it's simply one brush for a wall on top of another brush for the floor. Both properly aligned to grid with no overlapping.

    I do have some messed up curving walls elsewhere in the level which I haven't yet properly aligned, but they are in a different area altogether. Could they somehow be causing this?
     
  6. Odedge

    Odedge Keeper of Tutorials

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    The BSP tree is a mysterious thing and no one really knows what's going on with it! :lol:

    It's possible that a BSP issue somewhere else in the map is causing "an invisible wall" in a different area.

    I would make sure everything is snapped to the grid and you try to eliminate any intersecting brushes (unless you are doing BSP sinking).

    Also, keep the BSP brushes as simple as you can.
     
  7. Bazzwano

    Bazzwano Hi, I'm Bryan

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    I had these issues back in the Ut99 days.. BSP holes or BSP errors they were those days. Generally this is why we work with simple BSP. That's what I believe anyway.
     
  8. meowcat

    meowcat take a chance

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    Don't forget that the way the engine calculates non-parallel collision cylinder movement along walls can cause snags due to overhead BSP/object additions/seams. When the engine goes to update the object's location (from what I can tell) it first performs a trace (with an extent equivalent to the pawn's collision cylinder size, a world coordinate aligned prism) in the direction of the expected movement. If a wall is encountered, at least one additional trace is performed in the same direction only that the Z value of the start and end locations are offset by the MAXSTEPHEIGHT defined in pawn (or actor?) which has typically been 35UU (note that when physics is phys_flying this offset appears to possibly be tested twice, once by adding the offset, and another by subtracting the offset), this is how walking up stairs is handled (there must be another trace performed to find the final height to adjust up as well). If an object is hit by the trace then the resultant movement is adjusted to move along parallel to the surface (surface normal "crossproducted" with Z axis, then maybe dotted with the movement vector), or sometimes treated as a "hard" hit and resultant movement is stopped/zeroed altogether.

    Since the trace extent prism is always world aligned, I think it would almost always come in contact with bsp walls that are angled because of its "corners". I remember reading somewhere over on the UDN that collision with static mesh actors is handled slightly differently (the radius of the collision cylinder component is taken into account more) so you may want to try placing an invisible flat static mesh "wall" along the surface a few UUs away from the BSP surface and see how it works if the blocking volume does not do the trick.
     
  9. guitarxe

    guitarxe New Member

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    I hope one day I'll understand more than a word of what you said in that first paragraph, but the trick with an invisible static mesh to cover my walls is a good one, thanks for that :)
     
  10. guitarxe

    guitarxe New Member

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    Any idea which package to look in for invisible meshes?
     
  11. Bi()ha2arD

    Bi()ha2arD Toxic!

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    just use any simple box mesh with colissions and set it to invisible? (checkbox bHidden under display)
     
  12. Odedge

    Odedge Keeper of Tutorials

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    Or use a blocking volume?
     
  13. Bi()ha2arD

    Bi()ha2arD Toxic!

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    Obviously. And I already said that in my first reply. But he asked where an invisible mesh was...
     
  14. guitarxe

    guitarxe New Member

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    Silly me, I found UN_SimpleMeshes a few minutes after posting my question.
    Putting a blocking volume gives me an even worse problem in the same area, but using the mesh works like a charm!

    Thanks a lot guys! I'm really glad even though the game is more or less dead there are still folks around to help out :D
     
  15. guitarxe

    guitarxe New Member

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    I thought I'd put this topic to final rest. After publishing the map and playing it in the actual game I do not get snagged on any surfaces anywhere. I am guessing that this problem only happens when playing in-editor, and that the publishing process gets rid of whatever was causing the problem.

    Thanks to everyone for your help!
     

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