Jump to content
Hash, Inc. Forums

Synchronized stride lengths


A:M Dave

Recommended Posts

Situations: I've wanted to do this most when a wheel on each side of a vehicle needs to turn at a rate commenserate with the path that it is following.

 

Usual solution: Ignore it and hope speed, distance, object occlusion and/or detail do not allow the viewer to see that the two sides are locked together around a corner as if they are on a solid axle connecting them. Typical construction is the vehicle has a center bone constrained to the vehicle path. An action with stride length gives the illusion of grip to the surface. Straight paths are fine, but curves are not accurate.

 

Wanted: A way for A:M to adjust stride length differentially depending on instantanious radius of curvature with the path and offset of the wheel from center in the action.

 

(I'll use the example of the front steering wheels of a buckboard)

 

Things I've tried:

1. Make a path for each wheel. Each wheel is modeled separately (or mirrored). The rest of the vehicle is a separate model. Make a stride length action for the wheels. In Chor, make two paths equidistant from each other. (Rotoscoping can help in path drawing, but if the vehicle path turns an off-camber corner around a hill, inaccuracies creep in.) Constrain wheels to respective paths and drop stride length Action on them. Assemble vehicle to "float" between them by way of Translate To constraints from vehicle to each wheel. An Orient Like constraint will probably also be needed.

Results: It takes some careful setup and layout, but the results are really close.

Shortcoming: The biggest problem is keeping the two wheels opposite each other. I have been leaving one Ease alone and have been trying to adjust the other to match by eye.

Is there a way to control the Ease of one path with the Ease of another?

Sure wish a model spline could be used as a stride length path in Chor. Sure wish a path could be made in an Action. Sure wish there was an "copy offset curve" function.

 

2. Use a vehicle constructed on center with straight line stride length. Use Poses for wheel turning. In Chor, adjust rate of wheel turn with Pose over the top of the Action and stride length motion.

Results: Doesn't work.

Shortcoming: The Pose overrides the Action. I haven't found a setting that blends the two.

 

3. Use on-center constructed vehicle. Poses for wheel turning. Forget stride length. Constrain vehicle to path in Chor and manually adjust rate of wheel turn (probably with repeating Action).

Results: Good for wheel slipping maneuvers.

Shortcomings: Laborious for good "traction" matching.

 

4. Avoid this situation and don't worry about it.

Results: No one will notice except me. :)

 

I like the certainty of approach #1. I've been thinking about relating some attribute to the center of the curve or some throttling bone, but I've never used the formula or multi-relationship-driver capability. Is there a good example anyone knows of to go dissect?

Link to comment
Share on other sites

Unless you plan to animate off- road vehicle that would drive for miles on the bumpy terrain and you plan to follow it everywhere it goes, I would strongly suggest option 4. It really doesn't matter how you will solve the problem if the movement looks convincing in the camera's eye...

 

I don't have any other vehicle sugesstion for simple reason that I've never animated any...

 

Drvarceto

Link to comment
Share on other sites

Join the conversation

You are posting as a guest. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...