jed 789 Posted January 15 Share Posted January 15 (edited) I saw a video on YouTube by a guy who makes kinetic art mobiles. He had an interesting one made out of toothed spirals, so I had a go at recreating it in C4D. I tried using a helix spline, but couldn't seem to get the objects to interact correctly, so I made a proper log spiral using tracer. The movement is generated using dynamics - there's one collider that's rotated in XPresso driving 2 rigid bodies. demo.c4d https://en.wikipedia.org/wiki/Logarithmic_spiral make log spiral.c4d Edited January 15 by jed added a file 6 Quote Link to post

rasputin 42 Posted January 15 Share Posted January 15 Whoa-- amazing! It was only when camera dollied back that I perceived what you had achieved. Amazing and very tricky to do. Is that a phi (golden ratio) spiral? 0 Quote Link to post

Igor 1,000,000 Posted January 15 Share Posted January 15 This is really awesome, nice job Jed. Keep them coming, its always interesting to see what you have to show and share. I would like to see those shared on the Market, just so they are not forgoten and burried inside forums. 0 Quote U Render Quality Assurance Specialist Link to post

jed 789 Posted January 16 Author Share Posted January 16 @rasputin I just used the general log spiral equation where angle is in radians, e is the natural log base (aka Euler's number 2.71828) and tweaked the constants a + k until it looked right. I tried using a helix and radial bias but the gears were jumping. I guess it's the properties of logs that makes it work. Also, when I added the struts, with a helix I had to use a spline on the step effector to make things fit, but with the log curve the struts fitted without a spline. I usually animate gears with XPresso, but with the varying radii that would be beyond my math skills. Dynamics to the rescue ! The video above is version 2 - I didn't like how dynamics had introduced a small collision gap, so after baking for TR I increased the teeth size. The dynamics is Compound Collision Shape, but with all the geometry it was too slow in the viewport. I added some switched off rigid body tags to parts that don't contribute to the dynamics calculation. Here's the video I got the design from. The guy has some good stuff eg non-circular gears I'm still trying to figure out square gears... 3 Quote Link to post

southpaw 86 Posted January 16 Share Posted January 16 Fantastic work Jed, If you havn't already, check out a book called "The power of Limits" It's quite old, but talks about geometry of nature. I've found it very interesting, although the math stuff is way over my head, but I think you should be able to translate alot of the content into your tests judging by the work posted here. There's also a Houdini artist named Serjan Burlak that does a lot of this kind of work, I found out about the book from a podcast he was a guest on. 0 Quote Link to post

Hrvoje 1,000,000 Posted January 17 Share Posted January 17 @jed Use formula spline to your advantage where you can enter formulas in parametric form. It is designed for that 0 Quote Scene Nodes Tutorial Link to post

jed 789 Posted January 17 Author Share Posted January 17 @Hrvoje can formula spline use polar coordinates ie radius + angle ? Spirals are easiest described (and understood) using polar vs cartesian. TBH I've never really understood what 't' is in formula spline. in math - y = f(x) ie y is a function of x in C4D x = f(t) ie x is a function of t y = f(t) ie y is a function of t 0 Quote Link to post

Hrvoje 1,000,000 Posted January 17 Share Posted January 17 As far as I can see, formula uses parametric equations. t is a form of time (not scene time), basically a range from 0 to 2 * Pi. Try this in formula spline 0 Quote Scene Nodes Tutorial Link to post

jed 789 Posted January 17 Author Share Posted January 17 I think we're going to have to agree to differ on this. 0 Quote Link to post

Hrvoje 1,000,000 Posted January 18 Share Posted January 18 @jed Err, not sure I follow? Differ on what? 0 Quote Scene Nodes Tutorial Link to post

jed 789 Posted January 18 Author Share Posted January 18 @Hrvoje I understand how to represent polar coords in cartesian in order to use formula spline. By 'differ' I meant you find it a good way to get a log spiral and I don't. Converting 1 equation with 2 variables into 2 equations with 3 variables - an extra unnecessary variable t - makes things more complex IMHO. Those 2 equations do not shout out 'spiral' to me, but the polar version does. I must admit that my approach to C4D is to use math, XPresso, Python etc and ignore built-in functions that I haven't bothered to learn about. A frequent comment on my stuff is 'there's a field that can do that'. I have, of course, never tried to learn fields... 0 Quote Link to post

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