tips for wiper animation - using constrains

[wannabeArtist]

Hello,

I am a total beginner with animation and after couple of hours of trial-and-error I decided to ask if I'm on the right track at all.
I had an idea to animate the wipers on my car model, but it seems I might have taken just a little too much to chew

1. I figured, I would want the wiper blade to stick to the windshield - I found the surface constrain and used that, even though I had to rebuild my windshield, because it was a polygon object.
Is there any smarter way to do this? Without using nurbs?

2. I parented the wiper to its arm and it seemed to work ok. But when I applied the surface constrain to the wiper, it broke of the arm!
How come? Is there an easy way to make the wiper stick to the arm and the surface?

Any general ideas or tutorial links for this sort of thing would be appreciated

Thanks!

Here are some screenshots:

[craft]

uhmmm i got an idea. let'me try and i'll hit you back in a moment


... ok, done.

i'll start off with some random nurbs, but this will apply to polygons aswell.


create a 2xn(as long as you want.. i'm using 4) polygon grid and aline it to your windshield like so, with the longer side pointing at where the wiper's rotation axis will be. Don't make it too wide - i might have overdone it in the pictures. it's better that the whole grid stays over the windshield when you animate the wiper


now go to deform>shrink wrap your grid to the windshiled. this will do the trick


now create 5(n+1) nulls. Use the constraint "object to cluster" in every one, to bind them to each vertex in the center edge loop of your grid. activate the tangent and normal


finally create a bone that runs from the rotation axis to the tip of your wiper. Parent the grid under the bone and we're done. try animating the wiper..

[wannabeArtist]

Wow, thanks a lot!

I will try it out and come back with the results...

[wannabeArtist]

Phew,

I have spent the whole morning with this, but so far I haven't got it to work.

I think there is a slight difference in your example and my setup - and I'm too much of a n00b to figure it out

In your example you draw a bone from the rotation point to the tip of the wiper (blade), but in my set up the wiper arm is rotated from one end and the other end is fixed to the center of the wiper blade. After couple of hours of trying to figure this out, I'm not even sure if that matters, but at least the result that I got is not quite there yet.

I followed your example other wise, but I extended the bone to the middle of the grid. In addition I constrained the effector of the bone to a curve, because I had some trouble of aligning the bone so that it would stay on top of the windshield when rotated.

Here are a couple of screens. At the beginning everything is quite nice:



Then the effector starts to move along it's path, still doing fine:



Here my incompetence starts to show



And it continues to the end of the curve:



Any further tips how to fix this are most welcome

[craft]

check this model out.. also added an extra control.

i tryed it again as you described (it's basicly the same thing, just the geometry is a but further out from the axis) and it worked just fine. plus i was using a windshield that's much more curved to make sure it would work work fine.

it's hard to know why it worked here and not there. maybe you didn't align the grid right, maybe you're using a different wrap method.
See inside the model i'm sending, check the constraints i'm using and stuff. ;) hope you can get yours working fine.
Another tip: the bone that controls de wiper doesn't need to be the bone that positions the arm. you can have a second bone, that runs from the center null in the wiper back to the axis, and make it stretchy just to compensate any subtle excentric movement. if it's slight enouth you won't even notice the stretch but you would notice if the axis bounced around, otherwise.

EDIT: how and here's the code to make a stretchy bone. add it as an expression to the bone's length:
ctr_dist(bone's name)., (effector's name).)
the system will complain you have a cyclic dependency. it's ok.

[wannabeArtist]

That's really helpful, thanks a lot!

I took a fast look at it and it looks great and yet simple enough. Tomorrow I will study in in detail and try to apply the same to my model. I'm pretty convinced I will get it right this time