A knee

Hi all

I’m entering the world of animation from the world of math and physics, and, as I see things, a knee is a basis of the walk. I have learned in the Cut-out Animation Tutorial how to make a knee: I fix the hips and vary two angles. But where will my foot end up? That’s not the way I want to walk. I want to set the foot position, and let Synfig calculate the angles. See here what I mean: youtube.com/watch?v=igCxjvWv8X4 . So I did this, and it was way too much math (for this mathematician), especially because there is no root or power function so I had to compute the root trough the exp and log functions (which make the left-right jump in the video I think), and there is no acos function so I had to get it from atan2 function… And the whole thing with parameters conversion is so cumbersome for any real math - some scripting would be so cool… But the biggest problem is that I don’t know how to reuse this work. I spent an evening making this one leg, now what if I want to animate a spider? Do I have to do everything from stretch for each leg, or is there any way to copy the whole parameters tree and change it’s input, i.e. connect it to different points, to make it work on another leg?

Hi Dragan,
although Synfig convert types is a very powerful thing and awesome things can be done with them I strongly don’t recommend to create automatic movements for living characters. At the end you will find that the effort is quite big for the results achieved. Maths in Synfig are worth for mechanical movements or even for movements government by classic physics (See the parabolic shot or the particles template). But for living characters the result will be very unpleasant. Also at the end of the day you find that the composition is rigged and you cannot use for other kind of movements and expressions. Please believe me, I’ve passed by that experience.

Apart of that I haven’t found a reliable way to reuse complex math composition in different places with different values. Maybe you want to take a look to a tutorial I did: synfig.sourceforge.net/wiki/Reus … ValueNodes but for complex convert types synfig tends to crash :frowning:

For a spider animation I would create the main poses of the walk cycle and use duplicated keyframes and translation for the movement. The effect would be very similar or even better and the flexibility is greater for sure.