PBDSolver#

PBDSolver 实现了 Position Based Dynamics (PBD，基于位置的动力学)，用于以快速、稳定的性能仿真布料、软体和粒子系统。

概述#

PBD 的工作原理：

  • Predicting particle positions (预测粒子位置)

  • Projecting constraint violations (投影约束违反)

  • Iteratively correcting positions (迭代校正位置)

  • Computing velocities from position change (根据位置变化计算速度)

Advantages (优势)：

  • Stability (稳定性): Unconditionally stable (无条件稳定)

  • Speed (速度): Fast iterative solving (快速迭代求解)

  • Controllability (可控性): Direct position control (直接位置控制)

支持的材料#

Material

Description

PBD.Cloth

Cloth/fabric simulation (布料/织物仿真)

PBD.Elastic

Soft elastic bodies (软弹性体)

PBD.Particle

Particle systems (粒子系统)

PBD.Liquid

Position-based fluids (基于位置的流体)

使用方法#

import genesis as gs

gs.init()
scene = gs.Scene(
    pbd_options=gs.options.PBDOptions(
        iterations=10,
        damping=0.99,
    ),
)

# Add cloth
cloth = scene.add_entity(
    gs.morphs.Mesh(file="cloth.obj"),
    material=gs.materials.PBD.Cloth(
        stretch_stiffness=0.9,
        bend_stiffness=0.1,
    ),
)

# Fix top edge
cloth.fix_vertices(y_max=0.99)

scene.build()

for i in range(1000):
    scene.step()

配置#

PBDOptions 中的关键选项：

Option

Type

Description

iterations

int

Constraint iterations (约束迭代次数)

damping

float

Velocity damping (速度阻尼)

gravity

tuple

Override gravity (覆盖重力)

约束类型#

PBD 使用多种约束：

  • Distance constraints (距离约束): Maintain edge lengths (保持边长)

  • Bending constraints (弯曲约束): Resist folding (抵抗折叠)

  • Volume constraints (体积约束): Preserve volume (保持体积)

  • Collision constraints (碰撞约束): Handle contacts (处理接触)

布料示例#

cloth = scene.add_entity(
    gs.morphs.Mesh(file="cloth.obj"),
    material=gs.materials.PBD.Cloth(
        stretch_stiffness=0.95,   # Resist stretching (抗拉伸)
        bend_stiffness=0.05,      # Allow bending (允许弯曲)
        thickness=0.01,           # Collision thickness (碰撞厚度)
    ),
)

另请参阅#