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To Epic: LODs?

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    To Epic: LODs?

    I'm just curious if the current LOD swapping system is final in UDK. I've noticed that the algorithm to swap the lod's produces horrible artifacts as both models are visible for about a second and then one drops out. You can see the coplanar faces crossing each other during the transition. This is visible in the editor, world and even the staticmesh preview window when zooming in and out.

    I also noticed that when viewing the LOD's for Epic's grass objects, you can actually see the original model dropping out pixel by pixel and it looks like some kind of digital 8-bit transition using bit mosaic blocks. I don't see that on my models because the LOD contains most of the same information as the original object and the grass literally drops individual blades in and out.

    I've used a lot of engines and I've seen a lot of methods. The best I have ever used fades one object out as the other object fades in. The produces a transition that isn't noticable to the player at all.

    I can't help but run around my world and my eyes keep jumping to all these crazy overlaps that appear and disappear all over the place as I'm trying to make good use of LOD's.

    At the very least, I feel it is a bug that both the original model and the LOD itself are drawn at the same time. If we're going to merely be popping them in and out of view with a simple visibility check, then at the very least this needs to happen at the same time for both models. This will produce very visible popping during gameplay, but at least it's not popping, a bunch of artifacts and then artifacts popping away.

    Another thing I've noticed is that I can't find anywhere to set the max draw distance of an object so that at a certain point it completely disappears. This would be a nice feature as it would help with large scale optimization. Again, other engines I've used give a setting for max draw distance and also fade distance so these objects will smoothly transition to invisible.

    These are just some suggestions. Perhaps there is a way to set how the LOD's transition and I just haven't found it yet.

    You should set the bUsedWithScreenDoorFade property in the Usage section of the Material's properties in order to get a dissolve transition behavior for LODs on primitives using the material. I believe you may also need to set bAllowScreenDoorFade=true in the [Engine.Engine] section of the DefaultEngine.ini file.

    MaxDrawDistance under Rendering in the component's properties controls how far away the mesh can be draw. CullDistanceVolumes can also control this on all objects within their bounds.


      Ah ok, that sounds like what I'm looking for.


        So I turned on the ScreenDoor Fading and it's what I explained is happening with the UDK foliage. It transitions by dropping it out pixel by pixel. It's not actually a fade out and it's ugly.