Remove the Shell plugin and integrate it into the engine.
PiperOrigin-RevId: 760688502 Change-Id: Ia70988d42b7edf571d7cb4a4f48f8fc50b51667d
This commit is contained in:
Alessio Quaglino
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Copybara-Service
Copybara-Service
parent
45fc15b844
commit
7edbdd0ad6
@@ -22,8 +22,6 @@ set(MUJOCO_ELASTICITY_SRCS
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elasticity.cc
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elasticity.h
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register.cc
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shell.cc
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shell.h
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)
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add_library(elasticity SHARED)
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@@ -18,15 +18,3 @@ Parameters:
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- `bend` [Pa]: bending stiffness.
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- `flat` [bool]: if true, the stress-equilibrium configuration is that of a straight cable; if false or unspecified, it is the configuration defined in the XML.
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- `vmax` [N/m^2]: If greater than zero, the cable is colored using mechanical stresses; the value represent the maximum stress in the color scale.
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### Shell
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Implemented in [shell.cc](shell.cc).
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The shell plugin discretizes an inextensible 2D continuum. It is intended to simulate the bending of plates where the stretching is negligible compared to other deformation modes.
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Parameters:
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- `young` [Pa]: Young's modulus.
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- `poisson` [Pa]: Poisson's ratio; if 0, then the material only opposed shear deformations; if near 0.5, then the material is nearly incompressible (rubber-like).
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- `thickness` [m]: shell thickness, used to scale the bending stiffness.
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@@ -14,13 +14,11 @@
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#include <mujoco/mjplugin.h>
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#include "cable.h"
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#include "shell.h"
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namespace mujoco::plugin::elasticity {
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mjPLUGIN_LIB_INIT {
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Cable::RegisterPlugin();
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Shell::RegisterPlugin();
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}
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} // namespace mujoco::plugin::elasticity
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@@ -1,154 +0,0 @@
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// Copyright 2023 DeepMind Technologies Limited
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include <cassert>
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#include <cmath>
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#include <cstdint>
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#include <cstdlib>
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#include <optional>
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#include <utility>
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#include <vector>
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#include <mujoco/mjplugin.h>
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#include <mujoco/mjtnum.h>
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#include <mujoco/mujoco.h>
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#include "elasticity.h"
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#include "shell.h"
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namespace mujoco::plugin::elasticity {
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namespace {
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// local tetrahedron numbering
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constexpr int kNumVerts = Stencil2D::kNumVerts;
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} // namespace
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// factory function
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std::optional<Shell> Shell::Create(const mjModel* m, mjData* d, int instance) {
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return Shell(m, d, instance);
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}
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// plugin constructor
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Shell::Shell(const mjModel* m, mjData* d, int instance)
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: f0(-1) {
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// count plugin bodies
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nv = 0;
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for (int i = 1; i < m->nbody; i++) {
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if (m->body_plugin[i] == instance) {
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if (!nv++) {
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i0 = i;
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}
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}
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}
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// count flexes
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for (int i = 0; i < m->nflex; i++) {
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for (int j = 0; j < m->flex_vertnum[i]; j++) {
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if (m->flex_vertbodyid[m->flex_vertadr[i]+j] == i0) {
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f0 = i;
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nv = m->flex_vertnum[f0];
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if (m->flex_dim[i] != 2) { // SHOULD NOT OCCUR
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mju_error("mujoco.elasticity.shell requires a 2D mesh");
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}
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}
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}
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}
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// loop over all triangles
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for (int t = 0; t < m->flex_elemnum[f0]; t++) {
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int* v = m->flex_elem + 3*(t+m->flex_elemadr[f0]);
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for (int i = 0; i < kNumVerts; i++) {
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if (m->body_plugin[i0+v[i]] != instance) {
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mju_error("This body does not have the requested plugin instance");
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}
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}
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}
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// allocate array
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position.assign(nv*3, 0);
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// store previous positions
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mju_copy(position.data(), m->body_pos+3*i0, 3*nv);
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}
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void Shell::Compute(const mjModel* m, mjData* d, int instance) {
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for (int e = 0; e < m->flex_edgenum[f0]; e++) {
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int* edge = m->flex_edge + 2*(e+m->flex_edgeadr[f0]);
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int* flap = m->flex_edgeflap + 2*(e+m->flex_edgeadr[f0]);
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int v[4] = {edge[0], edge[1], flap[0], flap[1]};
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mjtNum force[12] = {0};
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if (v[3] == -1) {
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// skip boundary edges
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continue;
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}
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mjtNum* k = m->flex_bending + 16*m->flex_edgeadr[f0];
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for (int i = 0; i < StencilFlap::kNumVerts; i++) {
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for (int j = 0; j < StencilFlap::kNumVerts; j++) {
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for (int x = 0; x < 3; x++) {
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force[3*i+x] += k[16*e+4*i+j] * d->xpos[3*(i0+v[j])+x];
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}
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}
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}
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// update stored positions
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mju_copy(position.data(), d->xpos+3*i0, 3*nv);
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// insert into global force
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for (int i = 0; i < StencilFlap::kNumVerts; i++) {
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for (int x = 0; x < 3; x++) {
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d->qfrc_passive[m->body_dofadr[i0]+3*v[i]+x] -= force[3*i+x];
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}
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}
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}
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}
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void Shell::RegisterPlugin() {
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mjpPlugin plugin;
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mjp_defaultPlugin(&plugin);
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plugin.name = "mujoco.elasticity.shell";
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plugin.capabilityflags |= mjPLUGIN_PASSIVE;
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const char* attributes[] = {"damping"};
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plugin.nattribute = sizeof(attributes) / sizeof(attributes[0]);
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plugin.attributes = attributes;
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plugin.nstate = +[](const mjModel* m, int instance) { return 0; };
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plugin.init = +[](const mjModel* m, mjData* d, int instance) {
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auto elasticity_or_null = Shell::Create(m, d, instance);
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if (!elasticity_or_null.has_value()) {
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return -1;
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}
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d->plugin_data[instance] = reinterpret_cast<uintptr_t>(
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new Shell(std::move(*elasticity_or_null)));
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return 0;
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};
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plugin.destroy = +[](mjData* d, int instance) {
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delete reinterpret_cast<Shell*>(d->plugin_data[instance]);
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d->plugin_data[instance] = 0;
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};
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plugin.compute = +[](const mjModel* m, mjData* d, int instance, int type) {
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auto* elasticity = reinterpret_cast<Shell*>(d->plugin_data[instance]);
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elasticity->Compute(m, d, instance);
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};
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mjp_registerPlugin(&plugin);
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}
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} // namespace mujoco::plugin::elasticity
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@@ -1,61 +0,0 @@
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// Copyright 2023 DeepMind Technologies Limited
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef MUJOCO_PLUGIN_ELASTICITY_SHELL_H_
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#define MUJOCO_PLUGIN_ELASTICITY_SHELL_H_
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#include <optional>
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#include <vector>
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#include <mujoco/mjdata.h>
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#include <mujoco/mjmodel.h>
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#include <mujoco/mjtnum.h>
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#include "elasticity.h"
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namespace mujoco::plugin::elasticity {
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struct StencilFlap {
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static constexpr int kNumVerts = 4;
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int vertices[kNumVerts];
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};
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class Shell {
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public:
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// Returns a new Shell instance or nullopt on failure.
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static std::optional<Shell> Create(const mjModel* m, mjData* d,
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int instance);
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Shell(Shell&&) = default;
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Shell& operator=(Shell&& other) = default;
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void Compute(const mjModel* m, mjData* d, int instance);
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static void RegisterPlugin();
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int i0; // index of first body
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int f0; // index of corresponding flex
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int nc; // number of quads in the grid
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int nv; // number of vertices (bodies) in the Shell
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// precomputed quantities
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std::vector<mjtNum> position; // previous-step positions (nv x 3)
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private:
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Shell(const mjModel* m, mjData* d, int instance);
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};
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} // namespace mujoco::plugin::elasticity
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#endif // MUJOCO_PLUGIN_ELASTICITY_SHELL_H_
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