# Spinning screws in Fredo6 Animator

I’m doing an animation that shows the assembly of an object, mostly with screws. I thought it would be “cute” to have the screws spinning while being inserted.

I used the actual pitch of the screws for the pitch parameter of the screws. Actually, I had to multiply the pitch (distance screw should move in each 360 degree rotation) by a factor of 1000, since my model is 1000x.

But, in some instances, the screw doesn’t spin in the video made from the animation or spins the wrong way. Several instances look OK.

I suspect the issue is like watching a wagon wheel spin in a movie. The model is sampled at 25 FPS, so if the spin rate is a multiple of that, it will appear to be stationary. Which way it appears to spin just depends on how the frame rate and pitch + translation interact.

Does this seem right?

I don’t really care if the spin rate for a given translation is correct–just want to see them spin the right way in the animation.

Has anybody else seen this? Anyone have a suggestion of what pitch to use (or TPI) to use? j Probably needs to be a function of the total distance the screw moves and FPS of the movie…

Not meaning to be rude, but have you watched any classic cartoons lately?

I don’t see anything rude about your comment, but I’m Not sure how it helps or even your point.

Are you saying just don’t bother to have them spin? That’s the way I’m leaning, but it was simple enough to pick the “screw” movement versus just the translation.

I think what we makes more sense for my purpose is degrees rotation per frame. It’s probably pretty easy to calculate the pitch needed for that, given translation and frame rate. Just thought somebody had “been there, done that”.

So, here’s easy that works for my purpose.

Decide how many turns you want to see in the animation, 10 works well for me.

Divide the translation amount by the number of turns you want to see and use that for pitch. This will insure there won’t be 360 degrees or more rotation between frames.

Seems to work so far, many more to edit.

The strobing effect you describe happens quite readily with fast-moving objects and short or instantaneous “shutter speeds”. As @Box suggests, the easiest approach to lessen the stroboscopic effect is to fudge some aspect of the motion. Reduced rotation rate (as opposed to translation rate) is probably easiest to implement without losing the intended pace of the animation.

I put a lot of effort into minimizing the stroboscopic effect in a video I created with SketchUp a couple of years ago. I wanted to show some high-speed oscillation at real-time rate (using motion-blur to defeat strobing), and in slow motion (naturally no strobing). See the following topic for an explanation and video sample.

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That’s cool!

As I mentioned in the first post, I don’t care about the spin rate / pitch being accurate. I was just looking for an easy way to pick a pitch that would show the rotation and in the correct direction.

Calculating the pitch to get 10 or 20 rotations over the translation distance is working well for me. So I’m going to call my own post the solution.

Do not give too much credit to what you see in the user interface of Animator (where the animation is slower).

Could you generate the video and see what visual result you get.

But, in some instances, the screw doesn’t spin in the video made from the animation

Yes, I always make a short video clip for each screw movement. The screws spin the wrong way or not at all in the MP4.

But it’s due to the “strobing” effect as discussed in the posts above. I can get what I want to see by choosing a pitch that results in about 10 turns over the translation distance. Probably any pitch that prevents 360 degrees or more in a video frame would work fine.

But I love the Animator, Fredo 6!

One comment… the first video tutorial suggests making groups and components to facilitate the animation. I did that, even though I had to destroy the existing component hierarchy and group hierarchies in the model.

After getting close to the animation I want, I found the tutorial on “Kinematic Constraints”. Now that I know how to use Kinematic Constraints, I don’t really need (at least most of) the model modifications I did.

The first tutorial that suggests adding groups and components should also introduce kinematic constraints.

Admittedly, just a “newbie” issue, but having just getting started on Animator, I figured I give that feedback.

Again, love it!

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