I'd like to animate a metal rod being chopped in half ...

I want to animate a metal rod being cut in half by a blade, and I’d like to shoot it from the side so that you see the entire effect, and I’d like to do a close-up. Can shape-keys do this?

Shape keys can warp the object sometimes, you could try animating it yourself using bones for each bits. Or for a more physically accurate animation you could have it as two separate objects and then use the game engine to animate the cut. Start off with logic bricks keeping the breakaway bit under “Suspend Dynamics” so it isn’t affected by gravity or anything, then when the blade(or whatever) comes down, the contact restores the dynamics, and makes the bit of the bar fall.

Sorry if I’m not being very clear lol I’m not good at typing my thoughts out. I’ve got a video that goes through the logic brick set up for a similar thing (a glass being shattered by a ball bearing) so I can send you the link for that if you want. :slight_smile:

Actually, my particular requirement is much simpler: the blade comes down and slices a metal rod in half. The cut-away portion then moves forward down a conveyor while the back portion recoils slightly until the blade lifts again. There’s nothing real-time about this, and I’m (as usual) looking for cheeep and dirrrrty. (If need be, I’ll just do a few artful cuts with the video editor, but I’m kinda curious.)

:slight_smile:

Haha ok, well then I reckon you should just keyframe it in yourself. All the shape keys really help with is changing the vertices position on a mesh. But it doesn’t preserve volume so like I said can warp. So yeah try it out with keyframes, that’s my cheap and dirty suggestion :stuck_out_tongue:

Another way would be to use a boolean modifier. Use a thin cube to make the cut then select your cylinder and add a boolean modifier to it. Select Difference operation and your cube as the object.


Animate the movement of the cube so that it cuts at the same speed as the saw and then move the cube to another layer that is not rendered.


After the cut you will need to swap the cylinder so that the cut piece can move down the conveyor.

… and that’s what I wound up doing. Make three objects: the bar, and the two pieces. Keyframe the three exactly, at the moment when the cutter is fully-closed. No one will know ('cept us folks).