Need rig similar to a record player but much more complex

[RobH2]

I need to come up with a rig that is somewhat like a record player needle in a record groove but much more complex.

I've attached a video to show a simple description what I need to do. The video is keyframe animated by hand but it gets the point across.

I have a red spline on a disk(B). The disk turns like a record player but at about 1 revolution per 3 seconds. So, it's really slow. I need for the vertical object(A) to follow the red spline in, much like a needle on a record player, however, the red spline shape is not a nice concentric track like a record groove. In fact, in reality, it could get quite crazy and spaghetti like. See the blue(C) line? Let’s call that the ‘y’ axis.

I need to find a way to have (A) follow the red spline. But, (A) can only move in the y-axis as if it were retained by the slot in (D). So what I need to do is find out what the y-axis coordinate of the red line is (we always know the x-axis as it never changes) so I can send that to the y-axis of (A). So I guess what is happening is (A)’s y-axis is driven by the y-axis of the intersection of the red spline and (C).

I want to be able to animate the disk(B), forwards and backwards,  and see (A) move in and out while staying on top of the red spline.

[MedalHellWay]

very interesting ... I follow the discussion...

[Steve_Curley]

http://forums.autodesk.com/t5/Animation-and-Rigging/Simple-linking-question-driving-a-wedge-under-a-...
If you simplify the final solution slightly - one Dummy linked to the vertical post (a small distance away from it), shooting a ray along your C line towards the center of the turntable looking for the red spline. A small calculation should be able to move the post so it's sitting on the red spline. Have fun 😉

Actually, one of the earlier iterations of the controller script might be easier to understand, if the C line lies directly along X or Y.

IF you can't suss it out, post the example scene - much easier to work with when you have the "real deal" 🙂

[RobH2]

Steve,

Thanks for that. The long thread with James a few years back was indeed very helpful. I got it sort of working using that info. The lingering issue is that after one revolution when the red spline comes back around, the post snaps back to the beginning of it because 'PostDummy001' has not moved. I need to have it follow the post in as it moves towards the center.

I tried to solve it by creating a point at the post and linking the post to it. I then created another point and linked the PostDummy to it. That broke the system. I was going to link the points together so the PostDummyPoint would follow the PostPoint. So, I tried to write a script to have the PostDummy follow the Post with a small offset. I don't know MaxScript well enough to get the syntax correct. I can look at written code and interpret what's going on but do not currently have the knowledge to write it.

If I manually move the PostDummy in behind the Post as things are getting closer to the center, then it all seems to work. So, how can I set it up to have the PostDummy follow the post?

I've attached my file. [I tried everything to get the file, both .zip and .max to attach and kept getting the error: "The contents of the attachment doesn't match its file type."]  So, here is a link to it. Let me know if it's not accessible. I tired to open it up to everyone.

https://nvision4d.box.com/s/4e8jebn4m2vq2bf1ahcw

[Steve_Curley]

Apologies for the delay in replying - my a/c login got screwed and I couldn't log in to the proper account. Unfortunately for most members this has now been fixed 😄

Can't access that download I'm afraid - it wants a login 😞
I have had a play and may have a workable solution, but I'd like to try it on your scene before posting it (just in case).

[RobH2]

No problem Steve. Let me try to upload it again here. Maybe the maintenance last night did something funny.

Nope, can't attach. I wonder why. I've zipped it.

It continues to say "The contents fo the attachement doesn't match its file type."

Odd..

Ok, let me see how I can get the file to be available. I'll be back.

[RobH2]

Steve,

Since you are the only one helping me here I just PM'd you a link on my personal FTP site. Let me know if you get it downloaded.

Thanks

[Steve_Curley]

Did you do an Archive? That will include all the image files as well as the scene (not needed for my purposes). You can remove everything from (a copy of) the scene which is not directly related to the question.

Attached is NOT what I'm working on - it's a file from that other thread just to make sure uploads haven't stopped working 😉

[Steve_Curley]

Working ok for me...

[RobH2]

I have not made an archive but could. However, there are no assets with the sample file.

I'm trying to upload using IE instead of Firefox. Let's we what happens.

[RobH2]

Aaahaaa...Firefox it is the upload culprit. Hmmm...

[Steve_Curley]

Firefox 28.0 here... works as you can see. Got the file, will have a play 🙂

[RobH2]

Firefox 30.0 here and it fails to upload. IE 9 uploads perfectly. Haven't tried Chrome. I'll keep an eye on it.

Glad you got the file. No hurry. I appreciate your eye though....

[Steve_Curley]

This is tricky. Not the straightforward part of the spline, but the section where it doubles back on itself (around frame 350). Problem is that because the script is always looking along Y it fails at that point because the part of the spline it sees is not the part it's on but the next section it finds along Y, so it "jumps".

What we really need is the same as an object on a Path (with Follow) - it always turns to follow the direction of the spline, and I'm not sure quite how to do that. 😞

[RobH2]

Right you are. What I did was manually keyframe and move the post helper in towards the center, just closely following the post as it moved it. That works ok but it's not automatic. I still have to keyframe that. I could not find a way to link the helper to the post so that as the post is moving in, it dragged the helper in behind it.

A problem would occur though in the real world if the lines got too close toghther causing the helper to overlap several of them. It would not know which one to respect.