chenlin/Mujoco_WASM
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Remove edge length computations from elasticity plugins.

Browse Source 
Read the lengths from mjModel and mjData flex arrays.

PiperOrigin-RevId: 673116608
Change-Id: Iffa209abb7443707effaffb5bda99345399fac1c
This commit is contained in:
Alessio Quaglino
2024-09-10 14:53:31 -07:00
committed by Copybara-Service
parent e4d4153352
commit 33e56ccb88
5 changed files with 28 additions and 56 deletions
Download Patch File Download Diff File Expand all files Collapse all files
plugin/elasticity/elasticity.h
-22
View File
@@ -33,28 +33,6 @@ struct PairHash
}
};
inline mjtNum SquaredDist3(const mjtNum pos1[3], const mjtNum pos2[3]) {
mjtNum dif[3] = {pos1[0]-pos2[0], pos1[1]-pos2[1], pos1[2]-pos2[2]};
return dif[0]*dif[0] + dif[1]*dif[1] + dif[2]*dif[2];
}
inline void UpdateSquaredLengths(std::vector<mjtNum>& len,
const std::vector<std::pair<int, int> >& edges,
const mjtNum* x) {
for (int e = 0; e < len.size(); e++) {
const mjtNum* p0 = x + 3*edges[e].first;
const mjtNum* p1 = x + 3*edges[e].second;
len[e] = SquaredDist3(p0, p1);
}
}
inline void UpdateSquaredLengthsFlex(std::vector<mjtNum>& len,
const mjtNum* flexedge_length) {
for (int e = 0; e < len.size(); e++) {
len[e] = flexedge_length[e]*flexedge_length[e];
}
}
struct Stencil2D {
static constexpr int kNumEdges = 3;
static constexpr int kNumVerts = 3;
plugin/elasticity/membrane.cc
+13 -14
View File
@@ -14,6 +14,7 @@
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <optional>
#include <utility>
#include <vector>
@@ -164,32 +165,30 @@ Membrane::Membrane(const mjModel* m, mjData* d, int instance, mjtNum nu,
// allocate array
ne = edges.size();
reference.assign(ne, 0);
deformed.assign(ne, 0);
previous.assign(ne, 0);
elongation.assign(ne, 0);
force.assign(3*nv, 0);
// compute edge lengths at equilibrium (m->flexedge_length0 not yet available)
UpdateSquaredLengths(reference, edges, body_pos);
// save previous lengths
previous = reference;
}
void Membrane::Compute(const mjModel* m, mjData* d, int instance) {
mjtNum kD = damping / m->opt.timestep;
// update edge lengths
UpdateSquaredLengthsFlex(deformed, d->flexedge_length + m->flex_edgeadr[f0]);
// read edge lengths
mjtNum* deformed = d->flexedge_length + m->flex_edgeadr[f0];
mjtNum* ref = m->flexedge_length0 + m->flex_edgeadr[f0];
// m->flexedge_length0 is not initialized when the plugin is constructed
if (prev.empty()) {
prev.assign(ne, 0);
memcpy(prev.data(), ref, sizeof(mjtNum) * ne);
}
// we add generalized Rayleigh damping as decribed in Section 5.2 of
// Kharevych et al., "Geometric, Variational Integrators for Computer
// Animation" http://multires.caltech.edu/pubs/DiscreteLagrangian.pdf
for (int idx = 0; idx < ne; idx++) {
elongation[idx] = deformed[idx] - reference[idx] +
( deformed[idx] - previous[idx] ) * kD;
elongation[idx] = deformed[idx]*deformed[idx] - ref[idx]*ref[idx] +
( deformed[idx]*deformed[idx] - prev[idx]*prev[idx] ) * kD;
}
// compute gradient of elastic energy and insert into passive force
@@ -204,7 +203,7 @@ void Membrane::Compute(const mjModel* m, mjData* d, int instance) {
// update stored lengths
if (kD > 0) {
previous = deformed;
memcpy(prev.data(), deformed, sizeof(mjtNum) * ne);
}
}
plugin/elasticity/membrane.h
+1 -3
View File
@@ -53,9 +53,7 @@ class Membrane {
// precomputed quantities
std::vector<mjtNum> metric; // geom-induced metric (nt x 9)
std::vector<mjtNum> reference; // reference lengths (ne x 1)
std::vector<mjtNum> deformed; // deformed lengths (ne x 1)
std::vector<mjtNum> previous; // previous-step lengths (ne x 1)
std::vector<mjtNum> prev; // previous-step lengths (ne x 1)
std::vector<mjtNum> elongation; // edge elongation (ne x 1)
std::vector<mjtNum> force; // force at all vertices (nv x 3)
plugin/elasticity/solid.cc
+13 -14
View File
@@ -16,6 +16,7 @@
#include <cassert>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <optional>
#include <utility>
#include <vector>
@@ -171,32 +172,30 @@ Solid::Solid(const mjModel* m, mjData* d, int instance, mjtNum nu, mjtNum E,
// allocate array
ne = edges.size();
reference.assign(ne, 0);
deformed.assign(ne, 0);
previous.assign(ne, 0);
elongation.assign(ne, 0);
force.assign(3*nv, 0);
// compute edge lengths at equilibrium (m->flexedge_length0 not yet available)
UpdateSquaredLengths(reference, edges, body_pos);
// save previous lengths
previous = reference;
}
void Solid::Compute(const mjModel* m, mjData* d, int instance) {
mjtNum kD = damping / m->opt.timestep;
// update edge lengths
UpdateSquaredLengthsFlex(deformed, d->flexedge_length + m->flex_edgeadr[f0]);
// read edge lengths
mjtNum* deformed = d->flexedge_length + m->flex_edgeadr[f0];
mjtNum* ref = m->flexedge_length0 + m->flex_edgeadr[f0];
// m->flexedge_length0 is not initialized when the plugin is constructed
if (prev.empty()) {
prev.assign(ne, 0);
memcpy(prev.data(), ref, sizeof(mjtNum) * ne);
}
// we add generalized Rayleigh damping as decribed in Section 5.2 of
// Kharevych et al., "Geometric, Variational Integrators for Computer
// Animation" http://multires.caltech.edu/pubs/DiscreteLagrangian.pdf
for (int idx = 0; idx < ne; idx++) {
elongation[idx] = deformed[idx] - reference[idx] +
( deformed[idx] - previous[idx] ) * kD;
elongation[idx] = deformed[idx]*deformed[idx] - ref[idx]*ref[idx] +
( deformed[idx]*deformed[idx] - prev[idx]*prev[idx] ) * kD;
}
// compute gradient of elastic energy and insert into passive force
@@ -211,7 +210,7 @@ void Solid::Compute(const mjModel* m, mjData* d, int instance) {
// update stored lengths
if (kD > 0) {
previous = deformed;
memcpy(prev.data(), deformed, sizeof(mjtNum) * ne);
}
}
plugin/elasticity/solid.h
+1 -3
View File
@@ -51,9 +51,7 @@ class Solid {
// precomputed quantities
std::vector<mjtNum> metric; // geom-induced metric (nt x 36)
std::vector<mjtNum> reference; // reference lengths (ne x 1)
std::vector<mjtNum> deformed; // deformed lengths (ne x 1)
std::vector<mjtNum> previous; // previous-step lengths (ne x 1)
std::vector<mjtNum> prev; // previous-step lengths (ne x 1)
std::vector<mjtNum> elongation; // edge elongation (ne x 1)
std::vector<mjtNum> force; // force at all vertices (nv x 3)