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test.py
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591 lines (549 loc) · 23.6 KB
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import taichi as ti
import numpy as np
import random
import time
ti.init(arch=ti.gpu)
@ti.data_oriented
class sph_solver:
def __init__(self, x_list, flag_list, gui, dim=2, **kwargs):
# basic render settings
self.dim = dim
assert self.dim == 1 or self.dim == 2 or self.dim == 3
self.dim_size = ti.Vector([1, 1.02])
self.dt = 5e-4
self.gui = gui
# basic solver settings
self.r = 5e-3 # particle spacing
self.h = self.r * 2.0
self.nbrs_num_max = 500
self.grid_pnum_max = 500
self.theta_c = 0.025
self.theta_s = 0.0075
self.density = 400
self.snow_m = self.density * self.h ** 3
self.mu_b = 1.0
self.psi = 1.5
self.E = 140
self.mu = 0.2
self.omega = 0.5
self.epsilon = 10.0
self.error_rate = 1e-3
if 'theta_c' in kwargs:
self.theta_c = kwargs['theta_c']
if 'theta_s' in kwargs:
self.theta_s = kwargs['theta_s']
if 'density' in kwargs:
self.density = kwargs['density']
# inferenced settings
self.p_num = len(x_list)
self.grid_size = ti.ceil(self.dim_size / (2 * self.h)) + 1
self.kernel_sig = 0.
if self.dim == 1:
self.kernel_sig = 2. / 3.
elif self.dim == 2:
self.kernel_sig = 10. / (7 * np.pi)
elif self.dim == 3:
self.kernel_sig = 1 / np.pi
self.kernel_sig /= self.h ** self.dim
# particle attributes
self.x = ti.Vector(self.dim, ti.f32) # positions
self.v = ti.Vector(self.dim, ti.f32) # velocity
self.v_tmp = ti.Vector(self.dim, ti.f32) # velocity_star
self.rho = ti.var(ti.f32) # density
self.rho_0 = ti.var(ti.f32) # rest density of the current time
self.rho_tmp = ti.var(ti.f32) # density_star
self.a_other = ti.Vector(self.dim, ti.f32) # acceleration_other
self.a_friction = ti.Vector(self.dim, ti.f32) # acceleration_friction
self.a_lambda = ti.Vector(self.dim, ti.f32) # acceleration_lambda
self.a_G = ti.Vector(self.dim, ti.f32) # acceleration_G
self.pressure = ti.var(ti.f32)
self.flag = ti.var(ti.f32)
self.F_E = ti.Matrix(self.dim, self.dim, ti.f32)
self.L = ti.Matrix(self.dim, self.dim, ti.f32)
self.lbda = ti.var(ti.f32)
self.G = ti.var(ti.f32)
self.diag = ti.var(ti.f32) # a_ii for jacobi solver
self.vec_tmp = ti.Vector(self.dim, ti.f32)
self.var_tmp = ti.var(ti.f32)
self.lhs = ti.Vector(self.dim, ti.f32)
self.rhs = ti.Vector(self.dim, ti.f32)
self.mat_tmp = ti.Matrix(self.dim, self.dim, ti.f32)
self.p_solve = ti.Vector(self.dim, ti.f32)
self.v_solve = ti.Vector(self.dim, ti.f32)
self.res_solve = ti.Vector(self.dim, ti.f32)
self.s_solve = ti.Vector(self.dim, ti.f32)
self.t_solve = ti.Vector(self.dim, ti.f32)
ti.root.dense(ti.i, self.p_num).place(self.x, self.flag, self.v, self.v_tmp, self.rho, self.rho_0, self.rho_tmp,
self.a_other, self.a_friction, self.a_lambda, self.a_G, self.pressure,
self.F_E, self.L, self.lbda, self.G,
self.diag, self.vec_tmp, self.var_tmp,
self.lhs, self.rhs, self.mat_tmp, self.p_solve, self.v_solve,
self.res_solve, self.s_solve, self.t_solve)
self.nbrs_num = ti.var(ti.i32)
self.nbrs_list = ti.var(ti.i32)
nbrs_nodes = ti.root.dense(ti.i, self.p_num)
nbrs_nodes.place(self.nbrs_num)
nbrs_nodes.dense(ti.j, self.nbrs_num_max).place(self.nbrs_list)
# grid attributes
self.grid_p_num = ti.var(ti.i32)
self.grids = ti.var(ti.i32)
grid_nodes = ti.root.dense(ti.ij, (self.grid_size[0], self.grid_size[1]))
grid_nodes.place(self.grid_p_num)
grid_nodes.dense(ti.k, self.grid_pnum_max).place(self.grids)
# data initialize
self.rho.fill(self.density)
self.parallel_init(np.array(x_list), np.array(flag_list))
@ti.kernel
def parallel_init(self, pos_list:ti.ext_arr(), flag_list:ti.ext_arr()):
for i in range(self.p_num):
for j in ti.static(range(self.dim)):
self.x[i][j] = pos_list[i, j]
self.flag[i] = flag_list[i]
self.F_E[i] = ti.Matrix([[1, 0], [0, 1]])
@ti.func
def kernel(self, r):
sig, h = ti.static(self.kernel_sig, self.h)
q = r / h
assert q >= 0.
w = ti.cast(0.0, ti.f32)
if q <= 1.:
w = sig * (1. - 1.5 * q ** 2 + 0.75 * q ** 3)
elif q <= 2.:
w = sig * 0.25 * (2 - q) ** 3
return w
@ti.func
def kernel_grad(self, r):
sig, h = ti.static(self.kernel_sig, self.h)
q = r / h
assert q >= 0.0
dw = ti.cast(0.0, ti.f32)
if q <= 1.:
dw = sig * (-3. * q + 2.25 * q ** 2)
elif q <= 2.:
dw = sig * -0.75 * (2 - q) ** 2
return dw
@ti.func
def W(self, i, j):
r = self.x[i] - self.x[j]
w = self.kernel(r.norm())
return w
@ti.func
def dW(self, i, j):
r = self.x[i] - self.x[j]
dw = self.kernel_grad(r.norm())
return dw * r.normalized()
@ti.func
def bicgstab_vec_to_grad(self):
# vec_tmp -> mat_tmp
for i in self.x:
if self.flag[i] == 0:
grad_s = ti.Matrix([[0,0],[0,0]])
grad_b = ti.Matrix([[0,0],[0,0]])
for n in ti.static(range(self.nbrs_num[i])):
j = self.nbrs_list[i, n]
if self.flag[j] == 0:
grad_s += (self.v_tmp[j]-self.v_tmp[i]).outer_product(self.dW(i, j)) * self.snow_m / self.rho[j]
else:
grad_b += (self.v_tmp[j]-self.v_tmp[i]).outer_produce(self.dW(i, j)) / self.rho[j]
grad_tilde = grad_s @ self.L[i].transpose() + (grad_b @ self.L[i].transpose()).trace() / 3.
self.mat_tmp[i] = grad_tilde + (grad_b + grad_s).trace() / 3. - grad_tilde.trace() / 3.
@ti.func
def bicgstab_grad_to_vec(self):
# nabla dot sig
for i in self.x:
if self.flag[i] == 0:
self.vec_tmp[i].fill(0)
for n in ti.static(range(self.nbrs_num[i])):
j = self.nbrs_list[i, n]
dW_ij = self.dW(i, j)
if self.flag[j] == 0:
self.vec_tmp[i] += self.mat_tmp[j] @ (self.L[j] @ dW_ij) * self.snow_m / self.rho[j]
self.vec_tmp[i] += self.mat_tmp[i] @ (self.L[i] @ dW_ij) * self.snow_m / self.rho[j]
else:
self.vec_tmp[i] += self.mat_tmp[i].trace() / 3. * (self.L[i] @ dW_ij) / self.rho[j]
@ti.func
def bicgstab_rmat_update(self):
# mat_tmp -> vec_tmp
for i in self.x:
# update from grad to F_star
self.mat_tmp[i] = self.F_E[i] + self.dt * self.mat_tmp[i] @ self.F_E[i]
# F_star -> sig
self.mat_tmp[i] = 2 * self.G[i] * ((self.mat_tmp[i] + self.mat_tmp[i].transpose()) / 2. - 1)
@ti.func
def bicgstab_lmat_update(self):
for i in self.x:
if self.flag[i] == 0:
mat_prod = self.mat_tmp[i] @ self.F_E[i]
self.mat_tmp[i] = self.G[i] * (mat_prod + mat_prod.transpose())
@ti.kernel
def update_neighbors(self):
for p in self.x:
nbrs_num = 0
cell = (self.x[p] / (2. * self.h)).cast(int)
for dI in ti.static(ti.grouped(ti.ndrange((-1, 2), (-1, 2)))):
if all(0 <= cell + dI < self.grid_size):
for i in range(self.grid_p_num[cell + dI]):
nbr = self.grids[cell + dI, i]
if nbrs_num < self.nbrs_num_max and nbr != p and (self.x[p] - self.x[nbr]).norm() < 2 * self.h:
self.nbrs_list[p, nbrs_num] = nbr
nbrs_num += 1
self.nbrs_num[p] = nbrs_num
@ti.kernel
def to_grid(self):
for p in self.x:
cell = (self.x[p] / (2. * self.h)).cast(int)
cell_pnum = self.grid_p_num[cell].atomic_add(1)
self.grids[cell, cell_pnum] = p
@ti.kernel
def print_grids(self):
for i,j,k in self.grids:
if self.grids[i, j, k] > 1500:
print(i,j,k,self.grids[i,j,k])
@ti.kernel
def update_dt(self):
# update velocity
for p in self.x:
if self.flag[p] == 0:
self.v[p] += self.dt * (self.a_G[p] + self.a_other[p] + self.a_lambda[p] + self.a_friction[p])
# update fe
for p in self.x:
if self.flag[p] == 0:
grad_v = ti.Matrix([[0., 0.],[0., 0.]])
for nbr in range(self.nbrs_num[p]):
i = self.nbrs_list[p, nbr]
if self.flag[i] == 0:
grad_v += self.v[i].outer_product(self.dW(i, p))
self.F_E[p] += self.dt * grad_v @ self.F_E[p]
U, Sigma, V = ti.svd(self.F_E[p], ti.f32)
for n in ti.static(range(self.dim)):
Sigma[n, n] = min(1+self.theta_s, max(1-self.theta_c, Sigma[n, n]))
self.F_E[p] = V @ Sigma @ V.transpose()
# update position
for p in self.x:
if self.flag[p] == 0:
self.x[p] += self.dt * self.v[p]
@ti.kernel
def add_graivity(self, g: ti.f32):
for i in self.x:
if self.flag[i] == 0:
self.a_other[i][1] -= g
@ti.kernel
def check_dilation(self):
dilation = 0
for p in self.x:
if self.x[p][1] < 0.:
dilation+=1
self.x[p][1] = 0.
# self.v[p][1] = 0.
# if any(self.x[p]>1) or any(self.x[p]<0):
# dilation += 1
# for n in ti.static(range(self.dim)):
# self.x[p][n] = min(max(self.x[p][n], 0.), 1.)
# print("dilation = ", dilation)
# print("snow density = ", self.rho[0])
# print("boundary density = ", self.rho[self.p_num-1])
# print("neighbors_num = ", self.nbrs_num[0])
# print("neighbors = ", self.nbrs_list[0, max(self.nbrs_num[0]-1, 0)])
# print(self.kernel(0.005))
# print(self.kernel_sig)
i = 0
# print("acc_other:", self.a_other[i][0], self.a_other[i][1])
# print("acc_friction:", self.a_friction[i][0], self.a_friction[i][1])
# print("acc_lambda:", self.a_lambda[i][0], self.a_lambda[i][1])
@ti.kernel
def basic_solve(self):
"""friction & d_ii commented"""
# update density & L for all particles
# update rho for snow particles only
for i in self.x:
# prepare
# compute a_other
if self.flag[i] == 0 and self.x[i][1] <= 0.:
self.a_other[i].fill(0)
else:
self.a_other[i][1] = -50
m = 1 / (0.8 * self.h ** 2) # for boundary particles, rho = 1 / V
if self.flag[i] == 0:
m = self.snow_m
# self.a_friction[i] = self.v[i] + self.dt * self.a_other[i]
self.rho[i] = 0.0
self.L[i].fill(0)
d_ii = 1.0
# iteration
for n in range(self.nbrs_num[i]):
k = self.nbrs_list[i, n]
# compute density
if self.flag[k] == self.flag[i]:
self.rho[i] += self.W(i, k) * m
mass_k = 1.0
if self.flag[k] == 0:
mass_k = self.snow_m
self.L[i] += mass_k / self.rho[k] * self.dW(i, k).outer_product(self.x[k] - self.x[i])
if self.flag[i] == 0 and self.flag[k] != 0:
# compute friction only for boundary particles
# omit dynamic friction
x_ik = self.x[i] - self.x[k]
d_ii -= self.dt * self.mu_b * x_ik.dot(self.dW(i, k)) / self.rho[k] / (x_ik.norm() ** 2 + 0.01 * self.r ** 2)
# post processing
self.rho_0[i] = self.rho[i] * self.F_E[i].determinant()
self.L[i] = self.L[i].inverse()
# if self.flag[i] == 0:
# self.a_friction[i] = (self.v[i] + self.dt * self.a_other[i]) / (self.dt * d_ii)
# if i == 0:
# print(d_ii)
# compute lame parameters
for i in self.x:
if self.flag[i] == 0:
coef = ti.exp(self.epsilon * (self.rho_0[i]-self.density)/self.rho_0[i])
self.G[i] = self.E / (2 * (1 + self.mu)) * coef
self.lbda[i] = self.G[i] * self.mu * 2 / (1 - 2 * self.mu)
@ti.kernel
def implicit_state_solver(self):
"""
v_star -> v_tmp
rho_star -> rho_tmp
a_ii -> diag
grad_p -> vec_tmp
Ap_i -> var_tmp
"""
# PREPARE
# compute v_star
for i in self.x:
if self.flag[i] == 0:
self.v_tmp[i] = self.v[i] + self.dt * (self.a_other[i] + self.a_friction[i])
# self.v_tmp[i] = self.v[i] + self.dt * self.a_other[i]
else:
self.v_tmp[i].fill(0)
# compute rho_star and a_ii
for i in self.x:
if self.flag[i] == 0:
self.rho_tmp[i] = self.rho[i]
self.diag[i] = -self.rho_0[i]/self.lbda[i]
for m in range(self.nbrs_num[i]):
k = self.nbrs_list[i, m]
p_mass = 1
if m == 0:
p_mass = self.snow_m
self.rho_tmp[i] -= self.dt * self.rho[i] * (self.v[k]-self.v[i]).dot(self.dW(i, k)) * p_mass / self.rho[k]
dw_ik = self.dW(i, k)
if self.flag[k] == 0:
self.diag[i] -= self.dt ** 2 * dw_ik.norm() ** 2 * self.snow_m ** 2 / self.rho[i] / self.rho[k]
for n in range(self.nbrs_num[i]):
b = self.nbrs_list[i, n]
if self.flag[b] == 0:
self.diag[i] -= self.dt ** 2 * self.dW(i, b).dot(dw_ik) * self.snow_m ** 2 / self.rho[b] / self.rho[k]
else:
self.diag[i] -= self.psi * self.dt ** 2 * self.dW(i, b).dot(dw_ik) * self.snow_m / self.rho[b] / self.rho[k]
# SOLVE
while True:
error = 0
# compute grad_p
for i in range(self.p_num):
if self.flag[i] == 0:
self.vec_tmp[i].fill(0)
for m in range(self.nbrs_num[i]):
j = self.nbrs_list[i, m]
if self.flag[j] == 0:
self.vec_tmp[i] += (self.pressure[i] + self.pressure[j]) * self.dW(i, j) * self.snow_m / self.rho[j]
else:
self.vec_tmp[i] += self.psi * self.pressure[i] * self.dW(i, j) / self.rho[j]
# compute Ap and update
for i in range(self.p_num):
if self.flag[i] == 0:
self.var_tmp[i] = - self.rho_0[i] / self.lbda[i] * self.pressure[i] \
+ self.dt ** 2 * self.vec_tmp[i].dot(self.vec_tmp[i])
if abs((self.var_tmp[i] - self.rho_0[i] + self.rho_tmp[i])/(self.rho_0[i] - self.rho_tmp[i])) >= self.error_rate:
error += 1
if error == 0:
break
for i in range(self.p_num):
if self.flag[i] == 0:
self.pressure[i] += self.omega / self.diag[i] * (self.rho_0[i] - self.rho_tmp[i] - self.var_tmp[i])
# compute a
for i in self.x:
if self.flag[i] == 0:
self.a_lambda[i] = -self.vec_tmp[i]/self.rho[i]
@ti.kernel
def shear_deformation(self):
# update v_star_star
for i in self.x:
if self.flag[i] == 0:
self.v_tmp[i] = self.v[i] + self.dt * (self.a_other[i] + self.a_friction[i] + self.a_lambda[i])
# compute rhs
# -----------
# copy into
for i in self.x:
if self.flag[i] == 0:
self.vec_tmp[i] = self.v_tmp[i]
# compute
self.bicgstab_vec_to_grad()
self.bicgstab_rmat_update()
self.bicgstab_grad_to_vec()
# copy out
for i in self.x:
if self.flag[i] == 0:
self.rhs[i] = self.vec_tmp[i] / self.rho[i]
# compute lhs
# -----------
# copy into
for i in self.x:
if self.flag[i] == 0:
self.vec_tmp[i] = self.a_G[i]
# compute
self.bicgstab_vec_to_grad()
self.bicgstab_lmat_update()
self.bicgstab_grad_to_vec()
for i in self.x:
if self.flag[i] == 0:
self.lhs[i] = self.a_G[i] - self.vec_tmp[i] * self.dt / self.rho[i]
# initialize
rho_prev = 1
alpha = 1
omega = 1
for i in self.x:
if self.flag[i] == 0:
self.p_solve[i].fill(0)
self.v_solve[i].fill(0)
self.res_solve[i] = self.rhs[i] - self.lhs[i]
# iteration
while True:
rho = 0.
for i in self.x:
if self.flag[i] == 0:
rho += self.res_solve[i].dot(self.rhs[i]-self.lhs[i]) # l1
beta = (rho / rho_prev) * (alpha / omega) # l2
for i in self.x:
if self.flag[i] == 0:
self.p_solve[i] = self.rhs[i] - self.lhs[i] + beta * (self.p_solve[i] - omega * self.v_solve[i]) # l3
self.vec_tmp[i] = self.p_solve[i] # initialize for l4
# l4
self.bicgstab_vec_to_grad()
self.bicgstab_lmat_update()
self.bicgstab_grad_to_vec()
for i in self.x:
if self.flag[i] == 0:
self.v_solve[i] = self.p_solve[i] - self.dt ** 2 / self.rho[i] * self.vec_tmp[i]
# l5
alpha = 0
for i in self.x:
if self.flag[i] == 0:
alpha += self.res_solve[i].dot(self.v_solve[i])
alpha = rho / alpha
# l6
for i in self.x:
if self.flag[i] == 0:
self.a_G[i] += alpha * self.p_solve[i]
self.vec_tmp[i] = self.a_G[i]
self.bicgstab_vec_to_grad()
self.bicgstab_lmat_update()
self.bicgstab_grad_to_vec()
# l7
error = 0
for i in self.x:
if self.flag[i] == 0:
Ax = self.a_G[i] - self.dt ** 2 / self.rho[i] * self.vec_tmp[i]
if (Ax - self.rhs[i]).norm >= 0.1:
error += 1
if error == 0:
break
# l8
for i in self.x:
if self.flag[i] == 0:
self.s_solve[i] = self.rhs[i] - self.lhs[i] - alpha * self.v_solve[i]
self.vec_tmp[i] = self.s_solve[i]
self.bicgstab_vec_to_grad()
self.bicgstab_lmat_update()
self.bicgstab_grad_to_vec()
omega_up = 0
omega_down = 0
for i in self.x:
if self.flag[i]:
self.t_solve[i] = self.s_solve[i] - self.vec_tmp[i] * self.dt ** 2 / self.rho[i]
omega_up += self.s_solve[i].dot(self.t_solve[i])
omega_down += self.t_solve[i].dot(self.t_solve[i])
omega = omega_up / omega_down # line 10
for i in self.x:
if self.flag[i]:
self.a_G[i] += omega * self.s_solve[i] # line 11
self.vec_tmp[i] = self.a_G[i]
self.bicgstab_vec_to_grad()
self.bicgstab_lmat_update()
self.bicgstab_grad_to_vec()
error = 0
for i in self.x:
if self.flag[i]:
Ax = self.a_G[i] - self.dt ** 2 / self.rho[i] * self.vec_tmp[i]
self.lhs[i] = Ax
if (self.lhs[i]-self.rhs[i]).norm() >= 0.1:
error += 1
if error == 0:
break
def solve(self):
# refill neighbors
self.grid_p_num.fill(0)
self.nbrs_num.fill(-1)
self.to_grid()
self.update_neighbors()
# solve
self.basic_solve()
# self.implicit_state_solver()
self.update_dt()
self.check_dilation()
def render(self):
snow_p = []
pos_list = self.x.to_numpy()
for i, pos in enumerate(pos_list):
if self.flag[i] == 0:
snow_p.append(pos)
snow_p = np.array(snow_p)
self.gui.circles(snow_p, radius=1.5, color=0xEEEEF0)
self.gui.show()
def save(self, i):
snow_p = []
pos_list = self.x.to_numpy()
for j, pos in enumerate(pos_list):
if self.flag[j] == 0:
snow_p.append(pos)
snow_p = np.array(snow_p)
self.gui.circles(snow_p, radius=1.5, color=0xEEEEF0)
filename = f'frame_{i:05d}.png'
self.gui.show(filename)
print(i)
def add_particles(pos_bound, dx, dy, pos_list, flag_list, flag=0):
e = 1e-5
xl, yl, xr, yr = pos_bound
for x in np.arange(xl, xr, dx):
for y in np.arange(yl, yr, dy):
pos_list.append([x, y])
flag_list.append(flag)
def add_particles_random(pos_bound, p_num, pos_list, flag_list, flag=0):
xl, yl, xr, yr = pos_bound
for i in range(p_num):
pos_list.append([xl+random.random()*(xr-xl), yl+random.random()*(yr-yl)])
flag_list.append(flag)
def scene_init(snow_pnum, bound_dh):
pos_list = []
flag_list = []
# snow particles: flag=0 (randomized initialization)
add_particles_random([0.3, 0.05, 0.5, 0.25], snow_pnum // 3, pos_list, flag_list, flag=0)
add_particles_random([0.4, 0.37, 0.6, 0.57], snow_pnum // 3, pos_list, flag_list, flag=0)
add_particles_random([0.5, 0.69, 0.7, 0.89], snow_pnum // 3, pos_list, flag_list, flag=0)
# bound particles: flag=1 (regular initialization)
add_particles([0., 0.0, 1., bound_dh], bound_dh, bound_dh, pos_list, flag_list, flag=1)
# add_particles([0., 0., 0., 1.], bound_dh, bound_dh, pos_list, flag_list, flag=1)
# add_particles([1., 0., 1., 1.], bound_dh, bound_dh, pos_list, flag_list, flag=1)
return pos_list, flag_list
def mpm_main():
gui = ti.GUI('sph2d', res=512, background_color=0x112F41)
pos_list, flag_list = scene_init(9000, 5e-3)
test_solver = sph_solver(pos_list, flag_list, gui)
# while not gui.get_event(ti.GUI.ESCAPE, ti.GUI.EXIT):
start = time.time()
for i in range(600):
test_solver.solve()
# test_solver.print_grids()
# print(test_solver.grid_size)
test_solver.save(i)
print(600/(time.time()-start))
if __name__ == '__main__':
mpm_main()