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Compute moment of inertia for concave and boundary meshes. Resolve #338.

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- Mesh inertias can now be computed exactly for well-formed (no holes) non-convex meshes.
- To activate this feature, set `<compiler exactmeshinertia="true">` (defaults to `false`). This default may change in the future.
- Added `<geom shellinertia="true/false">` (defaults to `false`). When true, geom inertia is computed assuming all the mass is concentrated on the surface, and `density` is interpreted as surface density (mass/area). Currently only mesh geoms are supported.

PiperOrigin-RevId: 464368395
Change-Id: I17afd99b9b221c9d24ae951f6e63d5c61ff89820
This commit is contained in:
Alessio Quaglino
2022-07-31 04:31:46 -07:00
committed by Copybara-Service
parent 52d78f8d24
commit 5c5449bf82
19 changed files with 37807 additions and 272 deletions
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src/xml/xml_native_writer.cc
+6 -3
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@@ -253,13 +253,14 @@ void mjXWriter::OneGeom(XMLElement* elem, mjCGeom* pgeom, mjCDef* def) {
mjCMesh* pmesh = model->meshes[pgeom->meshid];
// write pos/quat if there is a difference
if (!SameVector(pgeom->locpos, pmesh->pos, 3) ||
!SameVector(pgeom->locquat, pmesh->quat, 4)) {
if (!SameVector(pgeom->locpos, pmesh->GetPosPtr(pgeom->typeinertia), 3) ||
!SameVector(pgeom->locquat, pmesh->GetQuatPtr(pgeom->typeinertia), 4)) {
// recover geom pos/quat before mesh frame transformation
double p[3], q[4];
mjuu_copyvec(p, pgeom->locpos, 3);
mjuu_copyvec(q, pgeom->locquat, 4);
mjuu_frameaccuminv(p, q, pmesh->pos, pmesh->quat);
mjuu_frameaccuminv(p, q, pmesh->GetPosPtr(pgeom->typeinertia),
pmesh->GetQuatPtr(pgeom->typeinertia));
// write
WriteAttr(elem, "pos", 3, p, unitq+1);
@@ -292,6 +293,7 @@ void mjXWriter::OneGeom(XMLElement* elem, mjCGeom* pgeom, mjCDef* def) {
WriteAttr(elem, "gap", 1, &pgeom->gap, &def->geom.gap);
WriteAttrKey(elem, "fluidshape", fluid_map, 2, pgeom->fluid_switch, def->geom.fluid_switch);
WriteAttr(elem, "fluidcoef", 5, pgeom->fluid_coefs, def->geom.fluid_coefs);
WriteAttrKey(elem, "shellinertia", meshtype_map, 2, pgeom->typeinertia, def->geom.typeinertia);
if (mjuu_defined(pgeom->_mass)) {
double mass = pgeom->GetVolume() * def->geom.density;
WriteAttr(elem, "mass", 1, &pgeom->mass, &mass);
@@ -657,6 +659,7 @@ void mjXWriter::Compiler(XMLElement* root) {
if (!model->usethread) {
WriteAttrTxt(section, "usethread", "false");
}
WriteAttrTxt(section, "exactmeshinertia", FindValue(bool_map, 2, model->exactmeshinertia));
}