A little mechanical modeling...

[dhartman]

Hi all! I was inspired by a recent post by David Dustin of Dustin Productions to attempt modeling and animating a bicycle chain moving around sprockets. So here it is!! I've attached screen shots which you can click to view larger images. Thanks David for the inspiration, and you're welcome to use my project if you have any use whatsoever!

 

BTW, I'm a little nervous, this is my first post to the Showcase, so here goes...but don't be afraid to criticize. (I hope my links show up correctly!)

 

My technique was to create a pose in which each chain link was constrained to path, with a different ease with keyframes at 0%, 50% and 100%. Then the sprockets were syncronized with the chain in an action. Finally, paint and chrome was applied (my favorite color by the way) and put in a choreography with a nice backdrop of graph paper.

 

The sprockets are in a 16:7 ratio. There's even a master link you can follow just so you know I didn't cheat--the entire chain is fully animated all the way around the path.

 

 

 

 

Here's the animation: 10-second clip of this rig in action. (5.2 mb)

 

And here's the project file. Enjoy!

[PlJack]

That is a beautiful thing Dhartman.

 

Superb work.

[pwknox]

The animation looks great. I'll be peeking at the project file soon.

 

Thanks for sharing.

[gschumsky]

Simply Amazing!!

 

Whoever said people can't do mechanical stuff with AM was smoking something illegal.

 

Keep up the great work!

 

Greg

[johnl3d]

Don't stay a newbie post more often!!!

[nimblepix]

Dan,

 

This is super!

Have you done this kind of thing before?

What's your background?

[Paul Forwood]

Excellent work, Dan. Thanks for posting here. I am sure alot of people will learn from this.

 

I can see from your website that you are not just a virtual engineer. You also do it in the real world. I used to do alot of lost wax casting in the past but have never tried sand casting or aluminium. I would love to have your setup though I don't think the insurance companies would like it much.

 

I look forward to seeing more of your work in the future.

[Rodney]

Great stuff! Thanks much for the project file too. That will help people understand how to achieve the effect more easily than thousands of words could.

 

Awesome!

 

I should mention that your entire setup and presentation is outstanding as well.

For those that might not know what I'm hinting at, the photographers backdrop (the curved mesh with grid) and the blue sky (default A:M background) are a hint at what you can do with backgrounds that are off camera. In this case creating the chrome effect.

 

From the example wireframe images to the project to the animation.

Well Done!

[starwarsguy]

I was going to say everything Rodney said! So.... GREAT WORK!

[frankH]

Thanks for sharing!!

[MATrickz]

Thats amazing!! I've never seen anyone do anything close to this with A:M! GREAT WORK!

[jesshmusic]

That is very nice. When I get home I will check out the animation, but I think the techinique sounds right. I like the idea a lot.

[R Reynolds]

First rate modeling and animation. But I'm curious about your modeling technique for the shaft ends. Is there any advantage to using peaked splines to assemble a four sided diamond other than avoiding the usual "infinitesimal" open 4 cp ring?

[ypoissant]

I think the shafts were made from my beveled primitives so I think I can answer.

 

In order to have a valid patch, it is not possible to use one single spline to close the cap. I could use 2 3CP splines and have a circular cap but I used a 4CP spline plus a 2 cp spline. And because the 2CP splines couldn't be rounded, I decided to peak the other spline too.

[ypoissant]

Very good work on this chain. I downloaded the project and I'm currious to see how you constrained and actioned the model. The idea of putting the chain in front of this curved graph paper makes a very slick image. Simple but effective design.

 

I observed a tiny hesitation where the chain have looped one turn. To avoid this, skip this last frame of your loop in chor.

 

Also, the chrome effect is nice but the background is a litle too uniform blue which produces flat reflections. I would suggest you cover your scene with a 100% ambiance (and there is something you needt to do to diffuse falloff too but I don't remember now) hemisphere onto which you set a gradient material that simulate the darker blue at zenith to paler blue (almost white) at horizon. This should produce nicer reflections. A darker plane for the ground would also help.

[Paul Forwood]

I observed a tiny hesitation where the chain have looped one turn. To avoid this, skip this last frame of your loop in chor.

 

I think you can remove about 62 or 63 frames to make it cycle, but I may have miscounted and I'm sure you knew that anyway.

[mediaho]

Brilliant!

[dhartman]

Thank you all for the input! It was a lot of fun to do, and although I spent a good bit of time working on it, it could be done again (or in more detail) in much less time, as I learned a great deal in the process.

 

I'll try to do a little dialog here to answer the questions:

 

Have you done this kind of thing before? What's your background?

 

I used A:M extensively in illustrating an technical book that I wrote, and that's where some of the practice came from. For the background, if you are referring to the graph paper, it's simply a pattern that I made in PaintShop Pro, and applied to the curved "ground" mesh. If you are asking about my educational / experience background, I do computer technical support / programming and website design for a living, and in a previous life, operated printing press (lotsa bicycle chains on them).

 

Reynolds: Is there any advantage to using peaked splines to assemble a four sided diamond other than avoiding the usual "infinitesimal" open 4 cp ring?

 

Yves: I think the shafts were made from my beveled primitives so I think I can answer.

 

I think Yves gets the credit here. The shafts are simply stretched cylinders straight from the primitives library that comes with the A:M disk.

 

I observed a tiny hesitation where the chain have looped one turn. To avoid this, skip this last frame of your loop in chor.

 

You're right, Yves, there is. In the action, I tried to correct this by looping the pose from 0% to 99%, rather than 0% to 100%. This made it worse. I think the ultimate problem is that the 100% pose isn't exactly identical to 0%. And I must go into some detail about how the path is set up. The path actually makes two complete turns. This is because the first link has to ease along the path from 0% to 50% on the path (don't confuse the ease percentage with pose percentage), while the last link eases from 50% to 100%. All the other links are somewhere in between.

 

A little work on these ease percentages should clear up the hesitation, if I'm understanding the problem correctly.

 

Also, the chrome effect is nice but the background is a litle too uniform blue which produces flat reflections.

 

Good observation. Interesting you mention it, I did actually try putting a decal of a photograph on a plane behind the camera, but for some reason it would not reflect in the chrome. I think it had something to do with the lighting, like there was not light coming from the photo. Maybe adding the 100% ambiance to a photo decaled mesh would put a nice realistic reflection on the chrome?

 

Thanks again to all of you for your observations and praises. More posts to come...

[dhartman]

I wrote:

The path actually makes two complete turns. This is because the first link has to ease along the path from 0% to 50% on the path (don't confuse the ease percentage with pose percentage), while the last link eases from 50% to 100%. All the other links are somewhere...

 

Actually, the last link (Bone31) eases from 48.3% to 98.35%. Bone32 does not have any cp's, it is just an invisible bone that serves as an "aim at" constraint target for Bone31. I couldn't use Bone1 to serve as the target because of being a circular constraint.

[John Bigboote]

I enjoyed that, thanks! I think I'll even have a looksy at the project...

 

Nice Stuff!

[pwknox]

I just looked at the design. Very sweet. I like the way that you constrained the links to a spline in the model rather than in a path in the chor. Makes a lot of sense that way.

 

I also like the slight bow in the chain path. I really adds to the realism.

 

How did you figure out the Ease percentages? Did you guess/nudge/guess/nudge or figure them mathematically?

[dhartman]

How did you figure out the Ease percentages? Did you guess/nudge/guess/nudge or figure them mathematically?

 

Rough positioning done with the spin button in the ease property. This has a resolution of 1, and from there it had to be wrangled with the number pad and lots of 2-place decimals. In hindsight, in the 50% and 100% values could have easily been figured out mathematically by adding 25 and 50 to the 0% values.

 

I have some ideas about how to eliminate all that in future bike chains, though, and use only whole numbers. Hint: a "tail" on the end of the path spline, that by pulling out longer or shorter, would space the links correctly. Hope you all follow, I know it sounds weird. Then, in theory, the chain would be limited to 49 links, using whole numbers for ease percents.

[Kamikaze]

Great model Dan....now I'll attach it to my chopper Im building for Biker Buildoff....(I wish) I am looking to start a new project though..

 

Michael