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66c9c8a | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 | # Copyright (c) 2022 NVIDIA CORPORATION. All rights reserved.
# NVIDIA CORPORATION and its licensors retain all intellectual property
# and proprietary rights in and to this software, related documentation
# and any modifications thereto. Any use, reproduction, disclosure or
# distribution of this software and related documentation without an express
# license agreement from NVIDIA CORPORATION is strictly prohibited.
###########################################################################
# Example Sim Neo-Hookean
#
# Shows a simulation of an Neo-Hookean FEM beam being twisted through a
# 180 degree rotation.
#
###########################################################################
import math
import os
import warp as wp
import warp.sim
import warp.sim.render
wp.init()
@wp.kernel
def twist_points(
rest: wp.array(dtype=wp.vec3), points: wp.array(dtype=wp.vec3), mass: wp.array(dtype=float), xform: wp.transform
):
tid = wp.tid()
r = rest[tid]
p = points[tid]
m = mass[tid]
# twist the top layer of particles in the beam
if m == 0 and p[1] != 0.0:
points[tid] = wp.transform_point(xform, r)
@wp.kernel
def compute_volume(points: wp.array(dtype=wp.vec3), indices: wp.array2d(dtype=int), volume: wp.array(dtype=float)):
tid = wp.tid()
i = indices[tid, 0]
j = indices[tid, 1]
k = indices[tid, 2]
l = indices[tid, 3]
x0 = points[i]
x1 = points[j]
x2 = points[k]
x3 = points[l]
x10 = x1 - x0
x20 = x2 - x0
x30 = x3 - x0
v = wp.dot(x10, wp.cross(x20, x30)) / 6.0
wp.atomic_add(volume, 0, v)
class Example:
def __init__(self, stage):
sim_fps = 60.0
self.sim_substeps = 64
sim_duration = 5.0
self.sim_frames = int(sim_duration * sim_fps)
self.sim_dt = (1.0 / sim_fps) / self.sim_substeps
self.sim_time = 0.0
self.lift_speed = 2.5 / sim_duration * 2.0 # from Smith et al.
self.rot_speed = math.pi / sim_duration
builder = wp.sim.ModelBuilder()
cell_dim = 15
cell_size = 2.0 / cell_dim
center = cell_size * cell_dim * 0.5
builder.add_soft_grid(
pos=wp.vec3(-center, 0.0, -center),
rot=wp.quat_identity(),
vel=wp.vec3(0.0, 0.0, 0.0),
dim_x=cell_dim,
dim_y=cell_dim,
dim_z=cell_dim,
cell_x=cell_size,
cell_y=cell_size,
cell_z=cell_size,
density=100.0,
fix_bottom=True,
fix_top=True,
k_mu=1000.0,
k_lambda=5000.0,
k_damp=0.0,
)
self.model = builder.finalize()
self.model.ground = False
self.model.gravity[1] = 0.0
self.integrator = wp.sim.SemiImplicitIntegrator()
self.rest = self.model.state()
self.rest_vol = (cell_size * cell_dim) ** 3
self.state_0 = self.model.state()
self.state_1 = self.model.state()
self.volume = wp.zeros(1, dtype=wp.float32)
self.renderer = wp.sim.render.SimRenderer(self.model, stage, scaling=20.0)
def update(self):
with wp.ScopedTimer("simulate"):
xform = wp.transform(
(0.0, self.lift_speed * self.sim_time, 0.0),
wp.quat_from_axis_angle(wp.vec3(0.0, 1.0, 0.0), self.rot_speed * self.sim_time),
)
wp.launch(
kernel=twist_points,
dim=len(self.state_0.particle_q),
inputs=[self.rest.particle_q, self.state_0.particle_q, self.model.particle_mass, xform],
)
for _ in range(self.sim_substeps):
self.state_0.clear_forces()
self.state_1.clear_forces()
self.integrator.simulate(self.model, self.state_0, self.state_1, self.sim_dt)
self.sim_time += self.sim_dt
# swap states
(self.state_0, self.state_1) = (self.state_1, self.state_0)
self.volume.zero_()
wp.launch(
kernel=compute_volume,
dim=self.model.tet_count,
inputs=[self.state_0.particle_q, self.model.tet_indices, self.volume],
)
def render(self, is_live=False):
with wp.ScopedTimer("render"):
time = 0.0 if is_live else self.sim_time
self.renderer.begin_frame(time)
self.renderer.render(self.state_0)
self.renderer.end_frame()
if __name__ == "__main__":
stage_path = os.path.join(os.path.dirname(__file__), "outputs/example_sim_neo_hookean.usd")
example = Example(stage_path)
for i in range(example.sim_frames):
example.update()
example.render()
example.renderer.save()
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