I've been playing on a server for a very long time now and I've gradually progressed from nicer and nicer "houses" I'm currently in the sky and decided on making a multi-sphere structure, so I put 6 sphere force fields at 32 radius with the projectors equidistant from a central point making the force fields about 10 blocks at the least from each other in an orientation like + from top/bottom/side 1 on top 1 on bottom and 4 in the middle in a 2x2 orientation with top and bottom fields the same distance above and bellow and camouflaged them as ice. (that took a while to calculate, frame up etc)
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It's really cool looking (har har) but it also caused my client to crash without a log when I tried to log on in the middle of the arrangement, I had to get the owner of the server to help me by defaulting my location to spawn again and then approach from a side to turn em all off one by one, owner also crashed without a log going near the middle from outside. This was on 1.4.7.
I don't have any logs to show and I know this isn't terribly specific but I imagine the problem is easy to re-create, just make a ton of huge force fields near each other (mine were not touching though) I imagine the problem was that there were so many blocks the client had to figure out at the same time it couldn't, all I saw when I joined was one chunk with the force fields mostly being the "defaut" stripy texture and parts being ice. I was instantly disconnected from the server according to our bot but I could fly around but not interact with anything for 10s~, it literally loaded one chunk, was really odd looking, could see my place from top to bottom but only 16x16 of it.