# Keeping the base line fixed

I am trying to animate the movement of a wheel turning. To do this, I thought of simply having the wheel element squash down and up and down and up. This movement, along with the forward motion of the vehicle, produces a pretty good impression that the wheels are turning.

So, I set the first keyframe in the up position, then go to a new cell and set a keyframe in the down position. For both keyframes, I make sure that the bottom edge of the wheel is exactly on the same level.

When I study over the movement, I can see that the wheel does not maintain the same bottom edge level. It moves slightly during the transition–down, up and then down again. This happens both in constant and non-constant settings. How can I keep this base line alignment the same?

I’m not totally sure I understand exactly how you are creating this effect but I suspect that this tutorial style article I did may help you. KEYFRAMING THE BOUNCING BALL. In it I walk the reader thru the steps of refining and tweaking keyframed actions until they have locked down the specific movement. Pay particular attention to the steps that convert computer generated inbetweens into keyframes there probably lies your answer. -JK

Thanks so much, JK, I’ll study it over and see if I can find the solution to my problem as well as a lot of good input that I don’t know.

Upon further experimentation, I believe the problem was that I had unchecked the option for linear splines in preferences. I had previously unchecked this so that TBS would automatically curve the splines for any movement hoping that this would give a more natural movement automatically. Once I had it set to linear splines, my problem was gone.

Great, by the way I watched some of your cartoons on Youtube and I really like your work. -JK

Thanks, JK! Since I posted those clips on YouTube I’ve done two more and am in the process of doing the first episode of a new series. But I’m not posting them as they are going to go for a new unfinished site sometime in the near future.

I did your entire tutorial and learned a lot! Once I finished it, I tried duplicating the same animation using a motion path as the basis of the bounce and then tweaked the keyframes for squash and stretch. It came out almost the same. There’s just so much to learn, not only how to use the software but animation principles–it’s a whole world of stuff! I’ve just been a 2D illustrator for years and haven’t really thought in terms of motion and scene planning, camera moves, etc. So it is quite a bit to get a handle on. But it is exciting seeing things come to life!

I look forward to seeing more of your work, and your progress as you continue your exploration. Also, thanks for the follow up post about the Create Linear Splines being un-checked. I learned something new from that myself and have already used that knowledge to help another TBS user solve a similar but slightly different problem. I had never experimented with that setting and therefore never really knew what effects it might create. I’m still not sure when if ever it would be useful to have it un-checked but I sure know why it is best to have it checked most of if not all the time based on what I’ve learned today. I’m really glad the tutorial was useful too, I’ll continue to try to write more in that style in the future. -JK

Sorry, i think my english is to bad to understand your tutorial. I didn’t understand, how to creat a “timing diagram”

Here is a link to a 4 part series I wrote on ANIMATION TIMING which explains how to understand and create timing diagrams. Hopefully you will find it useful. -JK

Thank you! I try to understand thoose great tutorials… ;D