Spline Tracking: Part Heading Is Not Correct

Hi Everyone,

I'm working on an animation, and I've tried several different ways to approach this. I decided that using spline tracking might be the best way, but I'm having a problem with the "straightaway" portion of the spline. I have a curve that was created from a quarter of a spline circle and then one segment was turned into a straightaway. The reason for this is that I have a bunch of parts for a mechanical animation that will rotate in and then go straight back for assembly. I originally tried to do these just using a full circle, but the parts weren't lining up where they needed to be (screws hitting screw holes crooked, timing was off between different screw rotations, etc.). I'm expecting the part that's following the spline to straighten out when the object pivot hits the point on the spline at the straightaway segment. I've created a rectangle that marks the spline point location where the straightaway segment starts, so I can see it more easily in top / side ortho views. So it's only there for a visual cue. Viewing the attached file and screenshot will show what I'm talking about better. Does anybody know why this is happening, or how to fix it so it does work properly?

I've tried adjusting some of the spline tracking settings in the tag and none of them help. I can't even figure out what changing the "segment" count does, as nothing happens either way. From the manual, I would expect it to only go from the one point to the next and not track down the whole spline, but that's not what it's doing. It still follows the whole spline. So that option seems useless. Unless it's not behaving the way it should, or I'm doing something wrong?

Also "Adjust just heading" isn't in the manual. So I can't tell what it does by checking and unchecking the box, as well as no description of it anywhere of what it should do.

There are a lot of parts that need to line up with each other (19 to be exact).

Any help will be greatly appreciated. Thanks!
 

Attachments

  • Spline Tracking Heading.jas.zip
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  • Spline Tracking Problem.jpg
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You can move the pivot point of the object forward until it's straight at the proper position.


Thanks Zoo!

Sorry for being daft, but I'm not sure exactly what you're meaning? Manually moving the pivot doesn't do anything until I "Burn pivot point". Doing that also throws off the spacing on my object(s) though. That will get tedious to manually adjust for all of the individual parts. I use the pivot points for measuring and calculating positions so all the parts line up and work in conjunction with each other when moving.

I don't think spline tracking is working correctly as it should though. I just tested it in C4d and it works as expected there. (If you're wondering why I don't just use that, it's because several of the animations in the series are already done in Cheetah and I want the renders to look the same. Some of the animation keyframes in C3d will not transfer via FBX / DAE either. So I can't export them out and just render in C4d to have them all match. Plus I'm still trying to learn to use C4d and don't have time to not finish these in the next couple of weeks.)

Also, I was going to test breaking the spline into segments, but I can't even get the "break segment" command to work.
 
Another thing I noticed.
If you move the control handles as close as you can to the control points
along the straight portion, the object will "straighten" sooner.

I can't figure out how to remove the control handles, but that would be best.
 
Another thing I noticed.
If you move the control handles as close as you can to the control points
along the straight portion, the object will "straighten" sooner.

I can't figure out how to remove the control handles, but that would be best.

Ah ok! I didn't even think about that. :cool:

Coming from using Illustrator nearly every day for 20 years, The length of the handles on a straight vector don't influence the path at all. So I didn't even think it mattered in C3d. I may even try a few more experiments using two separate spline segments that are part of the same group, but that are split on the ends. I think that's what the "All segments" is referring too. Not a continuous spline as I earlier thought.

Edit:
This is also really strange. All the spline points are still connected, but it's treating them as if they are two separate paths now. Which I would expect after splitting them, but the top segment shouldn’t still be joined to the curved part in that case. I can select the adjoining point, and it moves as if it's still one point connecting the segments.
 
Last edited:
The control point seem to be acting like F-Curves effecting the tracking angle.

That does sound strange, but I can't picture it.
 
You can "Snap to Component" the control handles to the control points.
But then you can't see the control point when you select it.
 
Thanks again, I appreciate you taking the time. I’ll have a look tomorrow when I’m back at work. Have a nice night!
 
I believe that´s because splines don´t know different point/node properties inside Cheetah3d like straight end-points for example.

Cheers
Frank
 
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