Motion Path Start Finish weird jump

# 1 07-05-2011 , 09:04 PM

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Making tank threads and have looked at many posts and tutorials but cant get motion path to work right. Used a nurb circle to create the motion path and its currently set to 0 to 400. I attach a tread and it works fine. It did flip upside down on the bottom half of the motion path but I fixed that with a locator and used object up. Problem is when I try attaching the next tread. I want the second tread to follow the first tread and a tutorial said to go into the graph editor, select the graph, hold down the shift key and the MMB and drag the graph to the right until the second tread is in the correct position. Then use the offset number each time you add a tread to the motion path by adding the offset to the start and finish positions.
My problem is I can drag the graph to the right but nothing moves. If I drag it to the left the tread moves forward and I have to drag the graph until the tread goes all the way around and ends up behind the first tread. This appears to work until the end of the motion path. The second tread stops before the end and the first tread passes it then the second tread jumps and catches up with the first tread then they go around together, then it repeats again.
Why wont the object move when I drag the graph to the right.
Also when I try offsetting the start end times it does not move the second tread to the correct position then does not animate, it just stays there.
Any help would be appreciated.

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# 2 07-05-2011 , 09:46 PM

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Try using the "creat animated snapshot" ctbram did a tutorial on a chain in free friday tutorials..........dave

Edit:I did use this to creat tank track in WIP some time ago

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Last edited by daverave; 07-05-2011 at 09:50 PM.

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# 3 08-05-2011 , 03:12 AM

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I watched the tutorial on how to make a chain using the Create Animation Snapshot and it worked great. Had to play with the Increment to get the spacing correct. Now when I try to animate the track I select the first tread and the nurb circle and attach to motion path. The tread disappears, when I hit the play button to see if there is a animation the tread appears in the background and moves around like a fly buzzing all over the place. Any suggestions on how I can now animate the treads.

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# 4 08-05-2011 , 06:20 AM

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Hi Mr Roboto
When I created tank tread I used ncloth to animate it (not saying you should do that). what happens if you just press play? if that does not work then I would do as below.
What I would do delete history, freeze transformation and delete old motion path and (might do) the same for the motion path...........dave

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Last edited by daverave; 08-05-2011 at 06:55 AM.

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# 5 08-05-2011 , 08:16 PM

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If I press play it moves off to the 0,0,0 and rotates as one object not individual track pieces.
I created a track using the increment number that I had to use in Create Animation Snapshot. Everything looked good until the last tread which overlapped the first one. What I have realized is that half way around creating the track the treads pivot point started going off the motion path. Don't know why this happened, as when I select any of the treads the pivot point is in the same place and I used duplicate for each tread. Do you know of a reason why it would go off the motion path and if so how to control it.

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# 6 08-05-2011 , 08:48 PM

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Sorry as much in the dark as you, have you got banking on the motion path, how did you create the curve was it in side or front vue. You can do little adjustment in the snap shot animater say 1.1 dont if that helps to fix that lst one ..........dave

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# 7 09-05-2011 , 09:45 AM

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OK so I found out what my problem is. The first problem with the weird jump was because I had not yet gone into the graph editor and changed the Tangent to Linear and the Curves Pre/Post Infinity to Curve. After I did that, that problem was fixed.
As for the treads going off the motion path I have discovered that there is something wrong with the tread itself. I created another NurbCircle without any deforming and attached a tread. It went off the path in spots again. Attaching a plain Cube it stays perfectly on the path. So I will recreate my tread as there must be something wrong with the geometry.
What I don't understand though is that when I did the Create Animation Snapshot the tread worked perfectly and stayed on the motion path all the way around.
Thanks for the help.

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# 8 09-05-2011 , 10:01 AM

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Did you delete the motion path history, this did happen to me when I used ncloth I had to clean all history.Is it happening when you go into the -Y. I think the is some history issue going on with the mesh, sorry I could not be of help.......dave

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# 9 10-05-2011 , 12:36 AM

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Originally I started out with a nurbcircle that I deformed using a lattice. I then duplicated the nurbcircle and deleted the original one and its lattice. This removed all history. I then rebuilt the nurbcircle. Because the tread was flipping all over the place the only way I could control it was using a locator. I did this by offsetting the nurbcircle and adding an object that became the locator. This worked fine for the first five treads. The sixth tread was too far away and started flipping again. So I put a locator every sixth tread. This worked fine.
The flipping of the tread was below the zero point or -Y.
If you could imagine a clock on the nurbcircle the treads rotated counterclockwise and started to go off the motion path around 1 o'clock and where at their furthest point from the motion path around 11 o'clock. They would gradually move back to the motion path about 5 o'clock. They all seemed to move up in the Y direction as if that end of the circle was dragged upwards, but it wasn't.
My motion path is O.K. because I can attach a cube and the pivot point is perfectly aligned to the motion path even if I move the pivot point around inside the cube. I will play with the tread to see if I can duplicate this problem. Right now I deleted everything except the motion path. I'll keep you posted.

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# 10 10-05-2011 , 07:21 AM

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One last try have you looked in the hypergrph editor or Outliner(show all)to see if there are any un explained nodes?...........dave

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Last edited by daverave; 10-05-2011 at 07:29 AM.

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# 11 11-05-2011 , 06:26 PM

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I now have a set of tracks that work. What I discovered is that the original tread that I made and manually placed each one individually around the wheels and sprockets to create a track was the problem. When I created a motion path and attached one of those threads it went off the motion path. For some reason it didn't when I did a Create Animation Snapshot. The only thing I can think of is that the first tread was placed at the start of the motion path and it just happened to be sitting on the motion path perfectly and the Create Animation Snapshot copied that all the way around.
I then started my second set of tracks using a tread from the ones created by Create Animation Snapshot. They worked perfectly. The only thing I should have done was created the first track in the correct position on the tank not off to the side. Reason being the tutorial said you cannot move it after creating it or it explodes, which it did. So I had to do a Duplicate Instance twice and move them into position, hiding the original one. I'll know next time. I'm very happy with how they turned out. Now I need to get the wheels and sprockets to rotate with them.
Thanks for your help.

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Last edited by Mr Roboto; 11-05-2011 at 07:52 PM.

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# 12 11-05-2011 , 09:06 PM

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Tank tread of a tiger I think, do a playblast I think thats the easest animation.......dave

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# 13 12-05-2011 , 12:27 AM

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Actually it's a Panther V that I'm working on. I did a Playblast as you suggested. It's over 300MB so I couldn't post it or email it but thanks for the tip.

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Motion Path Start Finish weird jump

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