StiffLengthConstraint¶

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

StiffLengthConstraint can be added between two objects as

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). Above code will create dynamics shown below

The type can be changed with the following command

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


By appending the above code and moving 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.