Aim constraint breaks half the time?

[toyyoda95]

I've been trying to use the aim constraint based on a friend's advice after finding nothing useful online. I'm not an animator but I need to make this work for a video for work. I got the aim constraint working on two cubes properly, so that cube 2 always faces cube 1 when I move it around. Then I did the same thing for my object and camera; the object always faces the camera as I move the camera around. However, when I try and constrain a second object, it's face 90 degrees away from the camera or straight up, no matter how I rotate or reset the object before adding. Changing the "-90" to "0" makes it face the camera at the moment, but as soon as I move the camera it goes back to
-90. Making a new set of cubes to mimic the first test, same results. New scene, same results; I'll get one to work but 3 others are broken. It isn't directional settings because some of them work, and I'm not getting any error messages or anything on the ones that aren't functioning properly. I've reset transformations and cleared history for all the items I've constrained and tried it with brand new untouched items. I've also repeatedly reset the aim constraint settings, but it's the default settings that did what I wanted when it worked. I'm trying to understand why SOME work and some don't when absolutely nothing has changed in the scene, no settings have been altered and it's all the same computer and program.. This shouldn't be happening - there should be an error, or all should be working, or none should since it's all the same objects and same scene and same constraint and same settings. Unfortunately, I can't just group the things I want (I need them to individually turn to face the camera, not face it collectively as a group), and duplicating copies the constraint but that copied constraint has no effect and doesn't work, so I have to apply constraints individually. I've looked online but haven't found any relevant information (it's not flipping around constantly like Maya has a page about, and it's not 180 opposite direction where you can just add/remove a - sign and fix it, because it's only translated 90 degrees). Any ideas? Am I missing something? Tutorials don't mention errors and the error forum posts don't mention this one, so I'm stumped. 

[toyyoda95]

In addition, sometimes it just works perfectly all the time. I've done 3 test scenes. One worked flawlessly for 20 items, one worked for the first few then caused issues on the third item and one didn't work correctly the first few times I applied aim, but after I tried a new item, it worked fine and let me add more just fine. In my original scene, it seemed to be working fine, but when I tried to add a second constrain to the camera it went all 90 degrees off, and after that even aim constraints on new items are wrong. In the test scene that worked well, I saved and closed the scene then reopened it, thinking maybe that saving or closing the scene was what was causing the issue, but it's still working as expected with no issues. In all cases, the items that applied aim correctly continue to function as normal and how I want them to, and the items that are 90 degrees rotated do react to the camera, just facing the completely wrong direction. I've tested items that were initially facing the constraint object/camera, as well as ones facing away (the item facing the camera turned 90 degrees to the left, but if I constrained it while facing 90 degrees to the right, it still flipped backwards to be facing left once constrained, so I couldn't cheat it). But I can't just keep making an entire new scene from scratch every time this pops up, I need to animate and render things, so I need to figure out why this issue keeps happening. 

[jmreinhart]

The axis of your objects might not line up with the model the way you think they do.

You should also look into the maintain offset options on the aimConstraint.

[toyyoda95]

Hi, 

I initially thought the issue might relate to direction, but it happened in multiple scenes with multiple objects facing multiple directions. So I wasn't able to make a firm connection where it never worked facing one direction or only worked facing another because it both worked and had errors in multiple scenes with multiple directions and orientations. I'm no expert, but I'm fairly sure I understand the orientations and directions of a default cube in a default scene, and that's what most of my test files were. Plus, like I said, I would freeze transformation and center pivot and delete history on objects (which directly effects orientation) and it had no effect. So I'm not sure what else I could do? I eventually got a file working but I still don't understand the problem, and I'd really like to understand the issue or limitations for next time.

Thanks. 

[Anonymous]

Just had this problem the other day. Try changing the rotate order of the child.

[toyyoda95]

Hi, I'm not sure what you mean? I didn't parent this when I applied the aim constraint, so there is no child, and I don't know what "rotate order" is referring to. Sorry if that's a dumb question. I did try changing the selection order, the orientation of objects, the direction objects were facing, the orientation of the pivot and editing the orientations in the aim constraint settings. None of it fixed the issue. The only things parented in my scene were the constraints themselves, which automatically became children of the objects they affected. 

I got a scene working eventually, but I still don't understand why that one worked when others didn't, or why some scenes would work for several objects then just break halfway through my list. So I'm trying to wrap my head around whatever the issues/limitations are to better understand it for next time. 

[evecoronado48]

I found that adjusting the Aim Vector in the aim constraint properties fixed this issue. It varied per objects, most will use the default. But if I got your error I changed the Aim Vector X to 0 and Y to 1.000