LookAt driving me insane!

[JamesLit]

I've scoured the internet for literally days and torn my hair out to no avail.







The images above show the 5 stages of the animation of the crosshead with the concerned parts showing. I'm not 100% au fait with the part names off the top of my head. As you can see, the bar attached directly to the crosshead at the bottom is level at the middle of the stroke, has a slight rise at the outward end of the stroke, and a large rise at the return end of the stroke.

The vertical part connected to it should follow it - you can see the section that attaches it to the aforementioned bit.

I have a three part system here - the two visible parts, plus a dummy object attached to the horizontal piece.



As the vertical piece pivots at a point further towards the centre of the locomotive (widthways) than the horizontal one, the dummy object has the same Y and Z coordinates as the part where the horizontal and vertical pieces join, but has the X coordinate of the pivot of the vertical piece. This means that the LookAt constraint is never pointing at an angle outwards or inwards, only back and forth.

As you can see from the 5 images demonstrating the animation, the vertical piece rotates not only back and forth as it should do on the X axis, but also left to right on the Y axis.

No matter what I try - whether it's the setup of the LookAt constraint itself, or the hierarchy system (disabling axes for example), etc etc, it seems to always do this. I have tried different set ups altogether, such as using bones instead, with exactly the same effect.

I have scoured through tutorials and forums and every single suggestion has fallen flat.

I have tried animating it manually but even with this number of frames to play with it just doesn't look good enough. Despite spending hours on calculations to try and get it spot on I can't accept it.

What on earth can I do?!

[TrabantDeLuxe]

Pics aren't working here!

[JamesLit]

Pics aren't working here!

Strange, I previewed the post to make sure they all worked. Gonna have to wait till tomorrow now... Thanks for looking though.

Sent from my X15 using Tapatalk

[VictoryWorks]

The images are returning a 403 forbidden code, meaning that we aren't logged in to the hosting site in the correct way. I suspect you need to make the links public to fix it so we can see them.

[JamesLit]

Sorted, hopefully!

[VictoryWorks]

Not sure how Max works but with the animations for rods, etc where they are always in-line along a single axis I always do mine by setting up emptys and armatures offset from the loco and that are all restrained along that single axis. I then either use them as parents for the model nodes or use constraints to tell the model nodes to copy only specific rotation axis or movement axis, but never the "static" axis.

Hope that makes sense? Sorry I can't give a more exact reply as it's not Blender but hopefully that might be enough to prompt a Max answer to the problem

[JamesLit]

I think I get what you're gunning at, there, mate... I'll have a play and report back!

[JamesLit]

Well, okay - it's a bit better, so far, sort of.

It no longer rotates on the Y or Z axes - fantastic!

Except now it rotates on the X axis even more... allow me to explain:
When the dummy object passes directly underneath the pivot point of the vertical section, going backwards, the vertical section itself decides to rotate 180 degrees on the X axis, meaning it is no longer visibly attached to the horizontal bar, instead interfering with the crosshead etc. Once it passes again going forwards, it reverts to its correct orientation. All the while, still following correctly the path of the dummy and swinging accordingly.

[VictoryWorks]

Assuming that the default rotation of the object is 0 and then it moves, for example to 100 degrees. Try rotating the verts in the node by half that (so 50 degrees in my example) so your final rotation goes from -50 to 50 rather than 0 to 100 degrees. Sometimes having it pass through 0 at it's mid point can produce less issues than having it start at 0.

[JamesLit]

Looks to me like I can't rotate the vertices, it just rotates the entire object itself, or if I select less than all of them, there's no change at all. The verts already pass through 0 though, rather than starting or ending there.