Fulcrum Points

 

Fulcrum points play a crucial role in the AutoPhysics simulation.

Overview

Fulcrum points represent parts of the character that contact the ground. A Point Controller is considered a Fulcrum Point when:

1. The point is close enough to the ground level. The Y coordinate for the point should not exceed the Collision radius value set for it:

2. Between the frames, the point does not move to a distance greater than the Max speed multiplied by the number of frames between the keys:

These parameters are parts of the Fulcrum point behavior which is by default applied to every Point Controller. They can be found on the Object Properties panel, under the Fulcrum Point tab:

If an interval has at least one fulcrum point, the character is considered to be standing on the ground.
The Point Controllers that are recognized as Fulcrum points are marked with a green borders for the character model (but not for the physics ghost):

Examples of Using Fulcrum Points

Manipulating Fulcrum Points can greatly affect the behavior of the AutoPhysics simulation.
For example, the simulation can make the character jump when you’re trying to make a squat:

Why does this happen?
If you look closely at the character’s legs, you’ll notice that they slide on the ground, moving backward:

Because of this, the AutoPhysics tool does not recognize them as fulcrum points.
And where there’s no fulcrum points, there’s only one kind of motion possible: ballistic motion, i.e., jumping.

But if we copy the feet positions from the frame 0 to the whole interval, they won’t move anymore, and a fulcrum area will appear:

As you can see, squats work correctly when there are fulcrum points.

So when you’d like to apply AutoPhysics to your animation, make sure that the animation has some fulcrum points.

And this is exactly why in most cases, AutoPhysics cannot work with stay-in-place animation.

Common Issues

Multiple Fulcrum Points

Having a big number of Fulcrum Points in a scene may cause issues.
Oftentimes, these issues can be fixed by decreasing the number of fulcrum points.

To do this:

1. Select a Point Controller that you don’t want to act as a fulcrum point.

2. Go to the Object Properties panel.

3. Open the Fulcrum point tab.

4. Set it to Not Fulcrum:

5. Repeat for every fulcrum point you’d like to disable.

 

See Also

AutoPhysics

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