How to animate a hierachy on a path? Like a train

[affarr]

Hi guys, Does anyone know if I can get mulitple objects in a hierachy to animate on a path one after another. Sort of like train cartridges moving on a track. Some solutions I thought of is to have each cartridges off set by a few frames. But then I cannot have them on a hierachyb4 I do that and also at different part of the path, the cartridges will sort of be pulled apart due to difference in distance between path vertices.

Thanks.

thanks.

[fredc]

In reply to:
Hi guys, Does anyone know if I can get mulitple objects in a hierachy to animate on a path one after another. Sort of like train cartridges moving on a track. Some solutions I thought of is to have each cartridges off set by a few frames. But then I cannot have them on a hierachyb4 I do that and also at different part of the path, the cartridges will sort of be pulled apart due to difference in distance between path vertices.

Thanks.

thanks.

Not much time at the moment, but I'll give you the overall approach. Just ask if you need more info.
The basic approach is to create a linear curve that matches the pivot points (ie: train cars) and then use a curve deformation to make it
translate along the path. I usually constrain a skeleton to the points of the linear curve, to make it easy to attach the actual geometry I want to
control such as train cars.
Part 1- Constrain a skeleton to a linear curve:

1. Turn on grid lock + S (off= shift + d).
2. Create a linear curve on the grid. This will very as to your needs in order to make each segment match the distance of your geometry.
3. Create a skeleton with each segment matching the segments of the linear curve.
4. Tag the first point of the linear curve. T is the hotkey for tagging points. You might turn on Show/unselected points if you want to always see the points on the curve, even if it isn't selected.
5. Use Tag/SetCluster then select New to create a cluster of just the first point.
6. Selecte the base of the skeleton. This will be attached to the linear curve.
7. Use Constraint/Object to cluster. This will attach the base of the skeleton to the first point in the curve.
8. Move the effector so the rest of the skeleton is not covering up the curve.
9. Tag only the second point of the curve. Use Tag/SetCluster again to create a new cluster.
10. Select the 2nd bone in skeleton then use Constrain/object to cluster again. Note: For a given bone, the "large" end is what gets consrained.
11. Repeat until all the bones are constrained. The skeleton effector will be the last part to constrain.

Part 2- Use Curve deformation to constrain the linear curve to the path
1. select the first point in the linear curve.
2. Use edit/center2verticies. This makes sure the center point of the curve is at the first point.
3. Translate the curve to 0,0,0, so that it starts from the scene origin.
4. rotate the curve so that it is pointing straingt up in the Y direction. Note: All curvce deformations use Y as the direction to follow curve.
5. Use Effect/Freeze all transformations. Always do this first before a curve deformation.
6. Select linear curve and then Deformation/Bycurve/Node/Create. This will deformat linear curve to path.
7. Reset the scale of the curve back to 1,1,1 if it is changed when you deform.

Part 3. Animating.
1. To animate the linear curve along the path, select the curve and use the Y translate.
2. Save a key at the start and end of the path by positioning the linear curve and using SaveKey/Object/NodeCurveDeformation/Translation.
You should now see you curve and skeleton move back and forth along the path as you scrub the time line.

We'll that's more than I had time for, but hopefully it was of use.
Let me or the others know if you need additional info.

Urp