Symmetry bug - Have a few mods loaded

[Jean Deaux]

I have a couple of mods loaded (see tagline) so I can't post this under Stock issues, but I've run into this problem consistently since .21 and wanted to report it to see if anyone running a stock version could test. I have discovered that if I create a branch of parts (with the symmetry feature turned off so that I'm only creating a single row of parts) that once I have a few parts in that grouping, if I select the lead part (and thus all parts attached to it) and then turn on the symmetry feature to repeat the assembly around the core part, that it creates a symmetry bug after you go to either the launch screen or reload your vehicle. In either case, the vehicle becomes corrupt and usually causes a system crash or lockup if you try to edit the part again.

The bug is that if one of the repeat features (I believe it to be the original grouping placed) gets duplicated atop itself the same number of times as the symmetry feature you selected. So if you had a fuel tank and engine and you selected a symmetry 6, you would have 6 repeats of the fuel tank and engine with just one of those locations having 6 of each component ontop of itself. You can't miss it, the parts will be much brighter than all the other components and will have mesh jumbling as they computer is trying to display them all at the same time (all this while in the VAB). On the launch pad, when the screen finally loads I typically see the ship falling to pieces and some of the parts laying on the ground or placed oddly within the ship with engines firing and under power. The ship will be oddly re-assembled, with about 80% of the ship with what you expected and the rest in a post-launch active and fallen state.

This bug usually doesn't "appear" as I activate the symmetry during assembly, it's only after I've launched or re-loaded the vehicle that the bug shows up. Usually when I try to edit the ship after the corruption, if I select any of the parts on the "stacked" arm, then will usually either lock up or become unable to deselect the part, drop the part, get a new part, or re-attach the part to anything. Only once was i actually able to deselect the parts, and that's where I noticed there were the same amount of parts in the stack as the number of symmetrical components, so there is an assumption on my part that a different number of symmetry will result in different stack quantities.

I know the quick response is, "don't build 'em that way stupid", but quite often with a bit of lag in the assembly process I'll grab a previously placed symmetrical component by accident and place it back, only to find the bug later on and have to scrap the design and start completely over again.

To be clear, mods I currently have loaded are Fuel Balancer V2.0, ISAMapsat X4R1, Kethane 7.7, Kerbal Alarm Clock 2.5, and Mechjeb 2.0.9.

Edited August 29, 2013 by Jean Deaux

[Jean Deaux]

Well, I went with the analogy that if you want something done right, best do it yourself. So I unloaded every mod I had and went back to stock and re-attempted the bug. You'll be pleased to know the stock game does not suffer from this bug so it is indeed a mod issue. Next I loaded up my mods one at a time so I could isolate the culprit.

And the winner is....

Mechjeb 2.0.9!!!!

I'll have to post in the Mechjeb forum in hopes they take notice of this issue.

[Jean Deaux]

Well dang, Mechjeb isn't the only add-on causing the bug as I've started playing again without Mechjeb and have run into this bug yet again. Guess I have more testing to do before I gear up for space travel again.

If it helps, here's a link to a ship file I was working on when it went corrupt. It's all stock parts and loads with the bug even with no mods loaded.

http://www.filedropper.com/stationcore2stock

[Jean Deaux]

Well this test turned out to be a bit of a suprise for me. I kept running into this bug rather randomly, sometimes a mod wouldn't cause it to appear, other times it would. What I began to take notice (mainly when I was attempting to get some play/design time in) is that the more parts I had in use, the higher my chances of the bug appearing. So what I opted to do was create a large model to first test the core KSP program to make sure it was working okay, and then move on to loading a single mod at a time to see if it caused the bug to appear.

Link to Test Ship module consisting of 1120 parts (have a well built high-end PC to load this baby) http://www.filedropper.com/test_9

I built the ship with no mods loaded, so obviously all stock parts, and would frequently save, load, launch, etc. to test and see if the bug showed up. As I expected, no bugs or problems occurred during the entire assembly process. Once I felt I had enough parts, I started to load one mod, test, close KSB, remove the mod, load another mod, launch KSP, repeat test... rinse, wash, repeat several times. What I was surprised to learn was that every single mod I tried resulted in the symmetry bug. I found this very odd and decided to try the stock version of the game and test in the same manner, sure enough the stock version of the game also resulted in the symmetry bug.

Here's how I performed my test....

First I selected one of the "branches" of the loaded file with Symmetry set to 1 (or off). This pulled all the other previous symmetry "branches" off the assembly and left me with but a single branch of parts.

Then with the main "branch" located where I wanted it, I turned on symmetry to 6 (using the "X" key) and then left click to place.

What I noticed in this process is that the parts never placed the first time I clicked, but the main "branch" would begin to act like it had, you can see the struts in this picture projecting up/outward for just one of the branches.

Moving the branch around a bit and returning to my desired location and clicking again allowed all the parts to be placed, and all seems well.

When you get to the launch pad, the ship forms oddly, you can see one of the engines branches on the ground and actually firing, even though I've yet to hit spacebar to activate the engines.

And finally back in the VAB, you can just see the closest fuel tank is brighter than all the others, because there's multiple parts atop each other there for every item in that particular symmetry branch. At this point the ship is corrupted and had you saved the ship design before launching, the file would be corrupt too.

So, I have to rescind my previous findings (sorry Mechjeb) as this looks like a core issue after all.

[Tiron]

Interesting. I've seen this bug before but this is the first time I've seen someone able to duplicate and document the process that spawns it.

So it's placing a singular, bugged article on the first click and then all of them on the second. That's interesting...

[Jean Deaux]

What's equally frustrating is that there's really only about 200-300 parts in this design, the remaining 820 or so parts are struts just to keep the ship together (which it doesn't yet do through a complete launch)