Animation Into Freefall Help

Hello everyone,

(Hopefully!) quick question. I have a scenario where I want a cube to push a sphere up a plane. One way I thought of doing this was to animate them both and do it in about 120 frames, it worked fine getting up there. What I want to happen here though is the cube pushes the sphere off the plane, and at that point, frame 121, I want the sphere to fall as if it were being dropped. I would normally do this by making it a Rigid Body Actor in the Logic section, and have manually placed balls on top of particle made grasshills with forces to push the grass around and it works fine.

My question, is there a way to at the 121st frame to start the game engine? If not, can I animate the cube to push the Rigid Body Sphere up the plane? It’s inclined, and for whatever inexperienced reason, the collision works fine between them, but the sphere just pushes the cube backwards (the animation doesn’t work in Game mode), and the Game Physics don’t work in animation.

Any help would be greatly appreciated!

You should be able to use the game engine for the whole process. You have the right idea about making both the cube and the sphere actors, but then you need to apply a constant force or constant speed to the cube. I’m not an expert in the GE, and I don’t have Blender here at the moment, so I can’t tell you the exact process, but you can set up a condition where pressing a key will apply a force to one of you actors in a given direction, and allow you to ‘steer’ it around. This will force it to push the sphere up the plane. (Actually, you might need to make an invisible ‘pusher’ that has a slight concave surface where the sphere sits, or it might roll around the cube regardless) Once you have that working, you can record the game movement as a set of IPOs, by setting the flag in the Game menu, and then go back to animation mode to tweak the IPOs as you like.



Ah, alright, I was thinking about using some sort of sensor / key input, and I do understand that method. I have since narrowed it down to a concise question / shortcoming that I think I was wondering if Blender can do:

I had a pendulum swing (ENTIRELY on animation key frames) and hit a soft body cube (like jello) and it hit it, bounced back, the jello jiggled, and I was like, “Yeah! I can just change it to a rigid body cube now and it’ll whack it like a (spherical) golf ball”! Am I wrong in saying this that an animation on key frames alone cannot actually move an object using the Bullet Physics? It always seems to go right through the object, yet when I roll a ball down a hill into a domino cube, it knocks it right over. That was using Game (P key). So the way to do what I’m thinking about with the pendulum would be to add a sensor / key input that would “release” the pendulum at the frame I need it to, record it with the IPO, and then work from there… correct? I’ve been using Blender for 4 days and really got into it and am a little unsure on the limitations of the key frame animation abilities alone.

Does this make sense?

Oh, and thanks a lot for your answer!

I think I understand you question. Basically, Game Physics knows nothing about animation IPOs at all. The converse is not true, in that you can ‘bake’ the game engine output into animation IPOs and edit them as an animation.

In your case you would need to work backwards: First animate the pendulum and the ball being knocked, or not, in the game engine, and bake those IPOs. THEN, go back and use those IPOs to feed into the softbody system to get your jello effect.

Of course, you can cut and paste the IPOs into a manual animation, but they are not easy to handle, as Blender generates a ‘keyframe’ for every frame of the game engine!