Source code for genesis.engine.materials.PBD.elastic

import gstaichi as ti

from .base import Base




@ti.data_oriented
class Elastic(Base):
    """
    The 3D elastic volumentric material class for PBD.

    Parameters
    ----------
    rho: float, optional
        The density of the elastic material (kg/m^3). Default is 1000.0.
    static_friction: float, optional
        Static friction coefficient. Represents the resistance to the start of sliding motion between two contacting particles.
        In collision resolution, it determines how much tangential force can be applied before sliding begins. Default is 0.15.
    kinetic_friction: float, optional
        Kinetic (Dynamic) Friction Coefficient. Represents the resistance during sliding motion between two contacting particles.
        Applied when particles are already sliding; limits the tangential force to simulate energy loss due to friction. Default is 0.0.
    stretch_compliance: float, optional
        The stretch compliance (m/N). Controls the softness of the stretch constraint between particles.
        Low values correspond to very stiff; enforces near-constant distance. High values correspond to softer response; more stretch allowed. Default is 0.0.
    bending_compliance: float, optional
        The bending compliance (rad/N). Controls how easily the material bends (e.g., at the fold of a cloth or edge of a soft body).
        Appears in inner edge constraints, determining how strongly the shape resists changes in angle. Default is 0.0.
    volume_compliance: float, optional
        The volume compliance (m^3/N). Determines how compressible a tetrahedral element is.
        Used in volume preservation constraints in 3D elastic or soft materials. Default is 0.0.
    stretch_relaxation: float, optional
        The stretch relaxation. Smaller value weakens the stretch constraint. Default is 0.1.
    bending_relaxation: float, optional
        The bending relaxation. Smaller value weakens the bending constraint. Default is 0.1.
    volume_relaxation: float, optional
        The volume relaxation. Smaller value weakens the bending constraint. Default is 0.1.
    """

    def __init__(
        self,
        rho=1000.0,
        static_friction=0.15,
        kinetic_friction=0.15,
        stretch_compliance=0.0,
        bending_compliance=0.0,
        volume_compliance=0.0,
        stretch_relaxation=0.1,
        bending_relaxation=0.1,
        volume_relaxation=0.1,
    ):
        super().__init__()
        self._rho = rho
        self._static_friction = static_friction
        self._kinetic_friction = kinetic_friction
        self._stretch_compliance = stretch_compliance
        self._bending_compliance = bending_compliance
        self._volume_compliance = volume_compliance
        self._stretch_relaxation = stretch_relaxation
        self._bending_relaxation = bending_relaxation
        self._volume_relaxation = volume_relaxation

    @property
    def rho(self):
        """The density of the elastic material (kg/m^3)."""
        return self._rho

    @property
    def static_friction(self):
        """Static friction coefficient."""
        return self._static_friction

    @property
    def kinetic_friction(self):
        """Kinetic friction coefficient."""
        return self._kinetic_friction

    @property
    def stretch_compliance(self):
        """The stretch compliance."""
        return self._stretch_compliance

    @property
    def bending_compliance(self):
        """The bending compliance."""
        return self._bending_compliance

    @property
    def volume_compliance(self):
        """The volume compliance."""
        return self._volume_compliance

    @property
    def stretch_relaxation(self):
        """The stretch relaxation."""
        return self._stretch_relaxation

    @property
    def bending_relaxation(self):
        """The bending relaxation."""
        return self._bending_relaxation

    @property
    def volume_relaxation(self):
        """The volume relaxation."""
        return self._volume_relaxation