raisim::DeformableObject::Material

struct · #include <raisim/object/deformable/DeformableObject.hpp>

Material and solver parameters.

Public attributes

totalMass

double totalMass

Total mass (kg). Positive. It is lumped onto the particles in proportion to the triangle area around each particle (one third of every incident triangle); a particle that belongs to no triangle receives the average share. Objects without triangles split it evenly, and filled meshes lump it by volume (see MeshParticleOptions::Mode::Filled).

distanceCompliance

double distanceCompliance

XPBD distance compliance. 0 is rigid, larger values are softer. Negative keeps backwards compatibility by using 1 / distanceStiffness.

distanceStiffness

double distanceStiffness

Legacy stiffness parameter. Prefer distanceCompliance for new code.

bendCompliance

double bendCompliance

Bending compliance (1/(N m)): the inverse of the bending modulus D of the surface. 0 is rigid, larger values fold more easily. Negative disables bending unless bendStiffness is positive. For an isotropic plate of thickness t, D = youngsModulus * t^3 / (12 (1 - poissonRatio^2)). The bending energy is quadratic in the curvature change from the rest shape, so curved rest shapes (shells, closed meshes) keep their shape.

bendStiffness

double bendStiffness

Bending modulus D (N m), used as 1 / bendCompliance when bendCompliance is negative. A positive value enables automatic adjacent-triangle bending constraints.

youngsModulus

double youngsModulus

Young's modulus in Pa. If positive, the mesh is a continuous isotropic elastic material with this modulus and poissonRatio (co-rotated linear elasticity: linear elasticity in a frame that rotates with the material), in place of the mesh-edge distance constraints and distanceCompliance. An object with tetrahedra (World::addDeformableVolume(), or a filled mesh, see MeshParticleOptions::Mode::Filled) is an elastic solid; otherwise the triangles form a membrane of the given thickness (plane stress). The extra distance constraints (struts, addDistanceConstraint()) get the compliance L / (E A) with the cross-sectional area A: with the default A = thickness * L, 1 / (E thickness) at every length, a zero-length weld included.

poissonRatio

double poissonRatio

Poisson's ratio of the membrane or solid (see youngsModulus), in (-1, 0.5). Close to 0.5 a solid is nearly incompressible.

thickness

double thickness

Membrane thickness (m), and the default cross-sectional area thickness * L of the extra distance constraints.

crossSectionArea

double crossSectionArea

Cross-sectional area of the extra distance constraints. If positive, it overrides thickness * L.

damping

double damping

Stiffness-proportional (Rayleigh) damping time (s), nonnegative. Every distance and bending constraint resists its rate of change with a viscous force equal to damping times its elastic stiffness (integrated implicitly), so a vibration mode of angular frequency w gets the damping ratio damping * w / 2: fast, stiff modes are damped more than slow ones. A rigid constraint (zero compliance) loses its whole rate. Rigid motion is not damped. Ignored in the PBD solver mode. Use airDrag for mass-proportional damping.

airDrag

double airDrag

Air drag rate (1/s), nonnegative. Every particle velocity decays as exp(-airDrag * t), so a free particle under gravity g approaches the terminal speed |g| / airDrag. 0 disables drag.

collisionRadius

double collisionRadius

Collision sphere radius of each particle (m). Positive.

iterations

int iterations

Constraint solver iterations per substep (nonnegative).

substeps

int substeps

Substeps per world step (positive). Deformables whose particles touch step together, with the largest substep count among them.

solverMode

SolverMode solverMode

Constraint projection scheme.

selfCollision

bool selfCollision

Collide the particles of this object with each other, except pairs that already overlap in the rest shape, so that a folded cloth rests on itself. Costs a neighbor search every step.