StiffLengthConstraint

StiffLengthConstraint is treated as a collision and solved using a contact solver. This ensures that the constraint is respected with high accuracy but is computationally costly (as if there is one more collision).

StiffLengthConstraint can be added between two objects as follows:

auto pin1 = world.addSphere(0.1, 0.8);
pin1->setPosition(0.0, 0.0, 3.0);
pin1->setBodyType(raisim::BodyType::STATIC);
auto ball1 = world.addSphere(0.15, 0.8, "steel");
ball1->setPosition(0.0, 0.1, 2.0);
auto wire = world.addStiffWire(pin1, 0, {0,0,0}, ball1, 0, {0,0,0}, 2.0);

By default, this constraint is STRETCH_RESISTANT_ONLY, which means that it acts like a string (i.e., it cannot push). The above code produces the dynamics shown below:

The stretch type can be changed with the following command:

wire->setStretchType(raisim::LengthConstraint::StretchType::COMPRESSION_RESISTANT_ONLY);

If you append the above code and move the ball higher, the simulation changes to:

The following code:

wire->setStretchType(raisim::LengthConstraint::StretchType::BOTH);

results in

This option resists both compression and stretch.

API

Class Reference

class StiffLengthConstraint : public raisim::LengthConstraint