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example_mesh.py
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168 lines (124 loc) · 4.76 KB
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# SPDX-FileCopyrightText: Copyright (c) 2022 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
###########################################################################
# Example Mesh
#
# Shows how to implement a PBD particle simulation with collision against
# a deforming triangle mesh. The mesh collision uses wp.mesh_query_point_sign_normal()
# to compute the closest point, and wp.Mesh.refit() to update the mesh
# object after deformation.
#
###########################################################################
import os
import numpy as np
from pxr import Usd, UsdGeom
import warp as wp
import warp.examples
import warp.render
@wp.kernel
def deform(positions: wp.array[wp.vec3], t: float):
tid = wp.tid()
x = positions[tid]
offset = -wp.sin(x[0]) * 0.02
scale = wp.sin(t)
x = x + wp.vec3(0.0, offset * scale, 0.0)
positions[tid] = x
@wp.kernel
def simulate(
positions: wp.array[wp.vec3],
velocities: wp.array[wp.vec3],
mesh: wp.uint64,
margin: float,
dt: float,
):
tid = wp.tid()
x = positions[tid]
v = velocities[tid]
v = v + wp.vec3(0.0, 0.0 - 9.8, 0.0) * dt - v * 0.1 * dt
xpred = x + v * dt
max_dist = 1.5
query = wp.mesh_query_point_sign_normal(mesh, xpred, max_dist)
if query.result:
p = wp.mesh_eval_position(mesh, query.face, query.u, query.v)
delta = xpred - p
dist = wp.length(delta) * query.sign
err = dist - margin
# mesh collision
if err < 0.0:
n = wp.normalize(delta) * query.sign
xpred = xpred - n * err
# pbd update
v = (xpred - x) * (1.0 / dt)
x = xpred
positions[tid] = x
velocities[tid] = v
class Example:
def __init__(self, stage_path="example_mesh.usd"):
rng = np.random.default_rng(42)
self.num_particles = 1000
self.sim_dt = 1.0 / 60.0
self.sim_time = 0.0
self.sim_timers = {}
self.sim_margin = 0.1
usd_stage = Usd.Stage.Open(os.path.join(warp.examples.get_asset_directory(), "bunny.usd"))
usd_geom = UsdGeom.Mesh(usd_stage.GetPrimAtPath("/root/bunny"))
usd_scale = 10.0
# create collision mesh
self.mesh = wp.Mesh(
points=wp.array(usd_geom.GetPointsAttr().Get() * usd_scale, dtype=wp.vec3),
indices=wp.array(usd_geom.GetFaceVertexIndicesAttr().Get(), dtype=int),
)
# random particles
init_pos = (rng.random((self.num_particles, 3)) - np.array([0.5, -1.5, 0.5])) * 10.0
init_vel = rng.random((self.num_particles, 3)) * 0.0
self.positions = wp.from_numpy(init_pos, dtype=wp.vec3)
self.velocities = wp.from_numpy(init_vel, dtype=wp.vec3)
# renderer
self.renderer = None
if stage_path:
self.renderer = wp.render.UsdRenderer(stage_path)
def step(self):
with wp.ScopedTimer("step", dict=self.sim_timers):
wp.launch(kernel=deform, dim=len(self.mesh.points), inputs=[self.mesh.points, self.sim_time])
# refit the mesh BVH to account for the deformation
self.mesh.refit()
wp.launch(
kernel=simulate,
dim=self.num_particles,
inputs=[self.positions, self.velocities, self.mesh.id, self.sim_margin, self.sim_dt],
)
self.sim_time += self.sim_dt
def render(self):
if self.renderer is None:
return
with wp.ScopedTimer("render"):
self.renderer.begin_frame(self.sim_time)
self.renderer.render_mesh(
name="mesh",
points=self.mesh.points.numpy(),
indices=self.mesh.indices.numpy(),
colors=(0.35, 0.55, 0.9),
)
self.renderer.render_points(
name="points", points=self.positions.numpy(), radius=self.sim_margin, colors=(0.8, 0.3, 0.2)
)
self.renderer.end_frame()
if __name__ == "__main__":
import argparse
parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument("--device", type=str, default=None, help="Override the default Warp device.")
parser.add_argument(
"--stage-path",
type=lambda x: None if x == "None" else str(x),
default="example_mesh.usd",
help="Path to the output USD file.",
)
parser.add_argument("--num-frames", type=int, default=500, help="Total number of frames.")
args = parser.parse_known_args()[0]
with wp.ScopedDevice(args.device):
example = Example(stage_path=args.stage_path)
for _ in range(args.num_frames):
example.step()
example.render()
if example.renderer:
example.renderer.save()