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detail_mujoco_parser.cc
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#include "drake/multibody/parsing/detail_mujoco_parser.h"
#include <algorithm>
#include <filesystem>
#include <limits>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
#include <fmt/format.h>
#include <tinyxml2.h>
#include "drake/common/text_logging.h"
#include "drake/geometry/proximity/obb.h"
#include "drake/geometry/proximity/obj_to_surface_mesh.h"
#include "drake/geometry/shape_specification.h"
#include "drake/math/rigid_transform.h"
#include "drake/math/rotation_matrix.h"
#include "drake/multibody/parsing/detail_make_model_name.h"
#include "drake/multibody/parsing/detail_tinyxml.h"
#include "drake/multibody/parsing/detail_tinyxml2_diagnostic.h"
#include "drake/multibody/tree/ball_rpy_joint.h"
#include "drake/multibody/tree/geometry_spatial_inertia.h"
#include "drake/multibody/tree/prismatic_joint.h"
#include "drake/multibody/tree/revolute_joint.h"
#include "drake/multibody/tree/scoped_name.h"
#include "drake/multibody/tree/weld_joint.h"
namespace drake {
namespace multibody {
namespace internal {
using drake::internal::DiagnosticPolicy;
using Eigen::Matrix3d;
using Eigen::Vector2d;
using Eigen::Vector3d;
using Eigen::Vector4d;
using geometry::GeometryId;
using geometry::GeometryInstance;
using math::RigidTransformd;
using math::RotationMatrixd;
using tinyxml2::XMLAttribute;
using tinyxml2::XMLDocument;
using tinyxml2::XMLElement;
using tinyxml2::XMLNode;
namespace {
constexpr std::array kOrientationAttributes = { // BR
"quat", "axisangle", "euler", "xyaxes", "zaxis"};
class MujocoParser {
public:
explicit MujocoParser(const ParsingWorkspace& workspace,
const DataSource& data_source)
: workspace_(workspace),
diagnostic_(&workspace.diagnostic, &data_source),
plant_(workspace.plant) {
// Clang complains that the workspace_ field is unused. Nerf the warning
// for now; it will be used soon.
unused(workspace_);
}
void ErrorIfMoreThanOneOrientation(const XMLElement& node) {
int num_orientation_attrs = 0;
for (const char* attr : kOrientationAttributes) {
if (node.Attribute(attr) != nullptr) {
++num_orientation_attrs;
}
}
if (num_orientation_attrs > 1) {
std::string attributes;
for (const XMLAttribute* attr = node.FirstAttribute(); attr;
attr = attr->Next()) {
attributes += fmt::format("{}={} ", attr->Name(),
fmt_debug_string(attr->Value()));
}
Error(node,
fmt::format(
"Element {} has more than one orientation attribute specified. "
"There must be no more than one instance of `quat`, "
"`axisangle`, `euler`, `xyaxes`, or `zaxis`. "
"Attributes: [{}]",
node.Name(), attributes));
}
}
// Any attributes from `default` that are not specified in `node` will be
// added to `node`. For orientation attributes, we do not apply orientation
// attribute defaults if the node already has an orientation attribute.
void ApplyDefaultAttributes(const XMLElement& default_node,
XMLElement* node) {
bool node_has_orientation_attr = false;
for (const char* attr : kOrientationAttributes) {
if (node->Attribute(attr) != nullptr) {
node_has_orientation_attr = true;
break;
}
}
for (const XMLAttribute* default_attr = default_node.FirstAttribute();
default_attr != nullptr; default_attr = default_attr->Next()) {
if (!node->Attribute(default_attr->Name())) {
if (node_has_orientation_attr &&
std::find_if(kOrientationAttributes.cbegin(),
kOrientationAttributes.cend(),
[&default_attr](const char* attr) {
return strcmp(attr, default_attr->Name()) == 0;
}) != kOrientationAttributes.cend()) {
// Don't apply default orientation attributes if the node already has
// an orientation attribute.
continue;
}
node->SetAttribute(default_attr->Name(), default_attr->Value());
}
}
}
RigidTransformd ParseTransform(
XMLElement* node, const RigidTransformd& X_default = RigidTransformd{}) {
Vector3d pos(X_default.translation());
ParseVectorAttribute(node, "pos", &pos);
ErrorIfMoreThanOneOrientation(*node);
if (node->Attribute("quat") != nullptr) {
Vector4d quat; // MuJoCo uses w,x,y,z order.
if (ParseVectorAttribute(node, "quat", &quat)) {
return RigidTransformd(
Eigen::Quaternion<double>(quat[0], quat[1], quat[2], quat[3]), pos);
}
}
Vector4d axisangle;
if (ParseVectorAttribute(node, "axisangle", &axisangle)) {
if (angle_ == kDegree) {
axisangle[3] *= (M_PI / 180.0);
}
return RigidTransformd(
Eigen::AngleAxis<double>(axisangle[3], axisangle.head<3>()), pos);
}
Vector3d euler;
if (ParseVectorAttribute(node, "euler", &euler)) {
if (angle_ == kDegree) {
euler *= (M_PI / 180.0);
}
Quaternion<double> quat(1, 0, 0, 0);
DRAKE_DEMAND(eulerseq_.size() == 3);
for (int i = 0; i < 3; ++i) {
Quaternion<double> this_quat(cos(euler[i] / 2.0), 0, 0, 0);
double sa = sin(euler[i] / 2.0);
if (eulerseq_[i] == 'x' || eulerseq_[i] == 'X') {
this_quat.x() = sa;
} else if (eulerseq_[i] == 'y' || eulerseq_[i] == 'Y') {
this_quat.y() = sa;
} else {
// We already confirmed that eulerseq_ only has 'xyzXYZ' when it was
// parsed.
DRAKE_DEMAND(eulerseq_[i] == 'z' || eulerseq_[i] == 'Z');
this_quat.z() = sa;
}
if (eulerseq_[i] == 'x' || eulerseq_[i] == 'y' || eulerseq_[i] == 'z') {
// moving axes: post-multiply
quat = quat * this_quat;
} else {
// fixed axes: pre-multiply
quat = this_quat * quat;
}
}
return RigidTransformd(RotationMatrixd(quat), pos);
}
Vector6d xyaxes;
if (ParseVectorAttribute(node, "xyaxes", &xyaxes)) {
if (xyaxes.head<3>().norm() < 1e-12) {
Error(*node,
fmt::format(
"The x axis in the 'xyaxes' attribute '{}' is too small.",
node->Attribute("xyaxes")));
return {};
}
if (xyaxes.tail<3>().norm() < 1e-12) {
Error(*node,
fmt::format(
"The y axis in the 'xyaxes' attribute '{}' is too small.",
node->Attribute("xyaxes")));
return {};
}
Matrix3d R;
// Normalize the x axis.
R.col(0) = xyaxes.head<3>().normalized();
// Make the y axis orthogonal to the x axis (and normalize).
double d = R.col(0).dot(xyaxes.tail<3>());
R.col(1) = (xyaxes.tail<3>() - d * R.col(0)).normalized();
// Make the z axis orthogonal to the x and y axes (and normalize).
R.col(2) = R.col(0).cross(R.col(1)).normalized();
return RigidTransformd(RotationMatrixd(R), pos);
}
Vector3d zaxis;
if (ParseVectorAttribute(node, "zaxis", &zaxis)) {
// Minimal rotation that maps the vector (0,0,1) into the vector specified
// here.
return RigidTransformd(
Eigen::Quaternion<double>::FromTwoVectors(Vector3d{0, 0, 1}, zaxis),
pos);
}
return RigidTransformd(X_default.rotation(), pos);
}
// Returns true if limits were parsed.
bool ParseLimits(XMLElement* node, const char* range_attr_name,
const char* limited_attr_name, Vector2d* limits) {
std::string limited_attr;
if (!ParseStringAttribute(node, limited_attr_name, &limited_attr)) {
limited_attr = "auto";
}
bool has_range = ParseVectorAttribute(node, range_attr_name, limits);
bool limited{false};
if (limited_attr == "true") {
limited = true;
} else if (limited_attr == "false") {
limited = false;
} else if (limited_attr == "auto") {
if (autolimits_) {
limited = has_range;
} else if (has_range) {
// From the mujoco docs: In this mode [autolimits == false], it is an
// error to specify a range without a limit.
Error(*node, fmt::format("The '{}' attribute was specified but "
"'autolimits' is disabled.",
range_attr_name));
}
} else {
Error(*node,
fmt::format("The '{}' attribute must be one of 'true', 'false', "
"or 'auto'.",
limited_attr_name));
}
return limited;
}
void ParseMotorOrPosition(XMLElement* node) {
std::string name;
if (!ParseStringAttribute(node, "name", &name)) {
// Use "motor#" as the default actuator name.
name = fmt::format("motor{}", plant_->num_actuators());
}
std::string joint_name;
if (!ParseStringAttribute(node, "joint", &joint_name)) {
Warning(*node, fmt::format(
"The motor '{}' does not use the 'joint' transmission "
"specification. Currently only the 'joint' attribute "
"is supported. This motor will be ignored.",
name));
return;
}
// Parse effort limits. For a motor, force limits are the same as control
// limits, so we take the min of the two.
double effort_limit = std::numeric_limits<double>::infinity();
Vector2d ctrl_range(0.0, 0.0), force_range(0.0, 0.0);
bool ctrl_limited =
ParseLimits(node, "ctrlrange", "ctrllimited", &ctrl_range);
bool force_limited =
ParseLimits(node, "forcerange", "forcelimited", &force_range);
if (ctrl_limited) {
if (ctrl_range[0] > ctrl_range[1]) {
Warning(
*node,
fmt::format(
"The motor '{}' specified a ctrlrange attribute where lower "
"limit > upper limit; these limits will be ignored.",
name));
} else {
effort_limit = std::max(ctrl_range[1], -ctrl_range[0]);
if (-ctrl_range[0] != ctrl_range[1]) {
Warning(*node,
fmt::format("The motor '{}' specified a ctrlrange attribute "
"where lower limit != -upper limit. Asymmetrical "
"effort limits are not supported yet, so the "
"larger of the values {} will be used.",
name, effort_limit));
}
}
}
if (force_limited) {
// For a motor, force limits are the same as control limits, so we take
// the min of the two.
if (force_range[0] > force_range[1]) {
Warning(
*node,
fmt::format(
"The motor '{}' specified a forcerange attribute where lower "
"limit > upper limit; these limits will be ignored.",
name));
} else {
effort_limit =
std::min(effort_limit, std::max(force_range[1], -force_range[0]));
if (-force_range[0] != force_range[1]) {
Warning(*node,
fmt::format("The motor '{}' specified a forcerange attribute "
"where lower limit != -upper limit. Asymmetrical "
"effort limits are not supported yet, so the "
"larger of the values {} will be used.",
name, std::max(force_range[1], -force_range[0])));
}
}
}
WarnUnsupportedAttribute(*node, "class");
WarnUnsupportedAttribute(*node, "group");
WarnUnsupportedAttribute(*node, "lengthrange");
WarnUnsupportedAttribute(*node, "cranklength");
WarnUnsupportedAttribute(*node, "jointinparent");
WarnUnsupportedAttribute(*node, "tendon");
WarnUnsupportedAttribute(*node, "cranksite");
WarnUnsupportedAttribute(*node, "slidersite");
WarnUnsupportedAttribute(*node, "site");
WarnUnsupportedAttribute(*node, "refsite");
WarnUnsupportedAttribute(*node, "user");
WarnUnsupportedAttribute(*node, "dyntype");
WarnUnsupportedAttribute(*node, "gaintype");
WarnUnsupportedAttribute(*node, "biastype");
WarnUnsupportedAttribute(*node, "dynprm");
WarnUnsupportedAttribute(*node, "gainprm");
WarnUnsupportedAttribute(*node, "biasprm");
const JointActuator<double>& actuator = plant_->AddJointActuator(
name, plant_->GetJointByName(joint_name, model_instance_),
effort_limit);
const char* gear_attr = node->Attribute("gear");
if (gear_attr) {
std::vector<double> vals = ConvertToVector<double>(gear_attr);
if (vals.size() != 1 && vals.size() != 6) {
Warning(*node, fmt::format("Expected either 1 value or 6 values for "
"'gear' attribute, but got {}.",
gear_attr));
}
if (vals.size() > 0) {
// Per the MuJoCo documentation: "For actuators with scalar
// transmission, only the first element of this vector is used."
plant_->get_mutable_joint_actuator(actuator.index())
.set_default_gear_ratio(vals[0]);
}
}
if (armature_.contains(actuator.joint().index())) {
const double gear_ratio =
plant_->get_joint_actuator(actuator.index()).default_gear_ratio();
plant_->get_mutable_joint_actuator(actuator.index())
.set_default_rotor_inertia(armature_.at(actuator.joint().index()) /
(gear_ratio * gear_ratio));
}
if (std::string_view(node->Name()) == "position") {
multibody::PdControllerGains gains{.p = 1, .d = 0}; // MuJoCo defaults.
double kp, kd;
if (ParseScalarAttribute(node, "kp", &kp)) {
gains.p = kp;
}
if (ParseScalarAttribute(node, "kd", &kd)) {
gains.d = kd;
}
plant_->get_mutable_joint_actuator(actuator.index())
.set_controller_gains(gains);
WarnUnsupportedAttribute(*node, "dampratio");
WarnUnsupportedAttribute(*node, "timeconst");
WarnUnsupportedAttribute(*node, "inheritrange");
}
}
void ParseActuator(XMLElement* node) {
for (XMLElement* motor_node = node->FirstChildElement("motor"); motor_node;
motor_node = motor_node->NextSiblingElement("motor")) {
ParseMotorOrPosition(motor_node);
}
for (XMLElement* position_node = node->FirstChildElement("position");
position_node;
position_node = position_node->NextSiblingElement("position")) {
ParseMotorOrPosition(position_node);
}
WarnUnsupportedElement(*node, "general");
WarnUnsupportedElement(*node, "velocity");
WarnUnsupportedElement(*node, "cylinder");
WarnUnsupportedElement(*node, "muscle");
}
void ParseJoint(XMLElement* node, const RigidBody<double>& parent,
const RigidBody<double>& child, const RigidTransformd& X_WC,
const RigidTransformd& X_PC,
const std::string& child_class = "") {
std::string name;
if (!ParseStringAttribute(node, "name", &name)) {
// Use "parent-body" as the default joint name.
name = fmt::format("{}-{}", parent.name(), child.name());
}
std::string class_name;
if (!ParseStringAttribute(node, "class", &class_name)) {
class_name = child_class.empty() ? "main" : child_class;
}
if (default_joint_.contains(class_name)) {
ApplyDefaultAttributes(*default_joint_.at(class_name), node);
}
Vector3d pos = Vector3d::Zero();
ParseVectorAttribute(node, "pos", &pos);
// Drake wants the joint position in the parent frame, but MuJoCo specifies
// it in the child body frame.
const RigidTransformd X_CJ(pos);
const RigidTransformd X_PJ = X_PC * X_CJ;
Vector3d axis = Vector3d::UnitZ();
ParseVectorAttribute(node, "axis", &axis);
// Drake wants the axis in the parent frame, but MuJoCo specifies it in the
// child body frame. But, by definition, these are always the same for
// revolute(hinge) joint and prismatic(slide) joint because the axis is the
// constraint that defines the joint. For ball joint and free joint, the
// axis attribute is ignored.
double damping{0.0};
ParseScalarAttribute(node, "damping", &damping);
std::string type;
if (!ParseStringAttribute(node, "type", &type)) {
type = "hinge";
}
Vector2d range(0.0, 0.0);
bool limited = ParseLimits(node, "range", "limited", &range);
JointIndex index;
if (type == "free") {
if (damping != 0.0) {
Warning(*node,
fmt::format(
"Damping was specified for the 'free' joint {}, but is not "
"supported for free bodies.",
name));
}
plant_->SetDefaultFreeBodyPose(child, X_WC);
} else if (type == "ball") {
index =
plant_
->AddJoint<BallRpyJoint>(name, parent, X_PJ, child, X_CJ, damping)
.index();
if (limited) {
WarnUnsupportedAttribute(*node, "range");
}
} else if (type == "slide") {
index = plant_
->AddJoint<PrismaticJoint>(
name, parent, X_PJ, child, X_CJ, axis,
-std::numeric_limits<double>::infinity(),
std::numeric_limits<double>::infinity(), damping)
.index();
if (limited) {
plant_->get_mutable_joint(index).set_position_limits(
Vector1d{range[0]}, Vector1d{range[1]});
// Note: MuJoCo does not clamp the reference position to stay inside
// the limits.
}
double ref{0.0};
ParseScalarAttribute(node, "ref", &ref);
plant_->get_mutable_joint(index).set_default_positions(Vector1d{ref});
} else if (type == "hinge") {
index = plant_
->AddJoint<RevoluteJoint>(name, parent, X_PJ, child, X_CJ,
axis, damping)
.index();
if (limited) {
if (angle_ == kDegree) {
range *= (M_PI / 180.0);
}
plant_->get_mutable_joint(index).set_position_limits(
Vector1d{range[0]}, Vector1d{range[1]});
// Note: MuJoCo does not clamp the reference position to stay inside
// the limits. This is important when the reference position defines
// constraints (as in the Cassie model in the menagerie.)
}
double ref{0.0};
if (ParseScalarAttribute(node, "ref", &ref) && angle_ == kDegree) {
ref *= (M_PI / 180.0);
}
plant_->get_mutable_joint(index).set_default_positions(Vector1d{ref});
} else {
Error(*node, "Unknown joint type " + type);
return;
}
// Note: The MuJoCo docs state that the armature is *always* added to all
// dofs of the inertia matrix: "Armature inertia (or rotor inertia, or
// reflected inertia) of all degrees of freedom created by this joint.
// These are constants added to the diagonal of the inertia matrix in
// generalized coordinates." But that is not what the rotor inertia of a
// motor actually does. In Drake we only add the rotor inertia through the
// joint actuator. This is a modeling difference.
double armature{0.0};
if (index.is_valid() && ParseScalarAttribute(node, "armature", &armature)) {
// Stash armature value to be used when parsing actuators.
armature_.emplace(index, armature);
}
WarnUnsupportedAttribute(*node, "group");
WarnUnsupportedAttribute(*node, "springdamper");
WarnUnsupportedAttribute(*node, "solreflimit");
WarnUnsupportedAttribute(*node, "solimplimit");
WarnUnsupportedAttribute(*node, "solreffriction");
WarnUnsupportedAttribute(*node, "solimpfriction");
WarnUnsupportedAttribute(*node, "stiffness");
WarnUnsupportedAttribute(*node, "margin");
WarnUnsupportedAttribute(*node, "springref");
WarnUnsupportedAttribute(*node, "frictionloss");
WarnUnsupportedAttribute(*node, "user");
}
// Computes a shape's volume, centroid, and unit inertia. This calculator is
// used in a context where the calculation of mass needs to be deferred (e.g.,
// density is not yet determined or mass has been explicitly specified). The
// caller is responsible for defining the final value for mass, e.g., using a
// parser-specified mass or density (or a fallback default density).
class InertiaCalculator final : public geometry::ShapeReifier {
public:
DRAKE_NO_COPY_NO_MOVE_NO_ASSIGN(InertiaCalculator);
// The reifier aliases the pre-computed mesh spatial inertias. When looking
// up mesh inertias, it uses the mujoco geometry _name_ and not the
// mesh filename.
InertiaCalculator(
const DiagnosticPolicy& policy,
std::string name,
std::map<std::string, SpatialInertia<double>>* mesh_inertia)
: policy_(policy),
name_(std::move(name)),
mesh_inertia_(mesh_inertia) {
DRAKE_DEMAND(mesh_inertia != nullptr);
}
// Returns the tuple [volume, p_GoGcm_G, G_GGo_G], where for a geometry G,
// volume is G's volume, p_GoGcm_G is the position from G's origin point Go
// to its centroid Gcm expressed in the G frame, and G_GGo_G is G's unit
// inertia about Go expressed in the G frame.
// Note: if G has uniform density, Gcm is G's center of mass.
std::tuple<double, Vector3d, UnitInertia<double>> Calc(
const geometry::Shape& shape) {
shape.Reify(this);
// For unit density (1 kg/m³), the value of mass is equal to the value of
// volume.
const double& volume = M_GGo_G_unitDensity.get_mass();
const Vector3<double>& p_GoGcm_G = M_GGo_G_unitDensity.get_com();
const UnitInertia<double>& G_GGo_G =
M_GGo_G_unitDensity.get_unit_inertia();
return {volume, p_GoGcm_G, G_GGo_G};
}
bool used_convex_hull_fallback() const {
return used_convex_hull_fallback_;
}
using geometry::ShapeReifier::ImplementGeometry;
void ImplementGeometry(const geometry::Mesh& mesh, void*) final {
if (mesh_inertia_->contains(name_)) {
M_GGo_G_unitDensity = mesh_inertia_->at(name_);
} else {
CalcSpatialInertiaResult result =
CalcSpatialInertiaImpl(mesh, 1.0 /* density */);
if (std::holds_alternative<std::string>(result)) {
policy_.Warning(std::get<std::string>(result));
// As this calculator is only used for Mesh shapes that are specified
// in a mujoco file, the mesh *must* be on-disk.
DRAKE_DEMAND(mesh.source().is_path());
// As with mujoco, failure leads to using the convex hull.
// https://github.com/google-deepmind/mujoco/blob/df7ea3ed3350164d0f111c12870e46bc59439a96/src/user/user_mesh.cc#L1379-L1382
result = CalcSpatialInertiaImpl(
geometry::Convex(mesh.source().path(), mesh.scale()),
1.0 /* density */);
if (std::holds_alternative<std::string>(result)) {
policy_.Error(fmt::format(
"Failed to compute spatial inertia even for the convex hull of "
"{}.\n{}",
mesh.source().path().string(), std::get<std::string>(result)));
} else {
M_GGo_G_unitDensity = std::get<SpatialInertia<double>>(result);
}
used_convex_hull_fallback_ = true;
} else {
M_GGo_G_unitDensity = std::get<SpatialInertia<double>>(result);
}
}
mesh_inertia_->insert_or_assign(name_, M_GGo_G_unitDensity);
}
void ImplementGeometry(const geometry::HalfSpace&, void*) final {
// Do nothing; leave M_GGo_G_unitDensity default initialized.
}
void DefaultImplementGeometry(const geometry::Shape& shape) final {
M_GGo_G_unitDensity = CalcSpatialInertia(shape, 1.0 /* density */);
}
private:
const DiagnosticPolicy& policy_;
std::string name_;
std::map<std::string, SpatialInertia<double>>* mesh_inertia_{nullptr};
bool used_convex_hull_fallback_{false};
// Note: The spatial inertia below uses unit density so that the shape's
// volume value is equal to its mass value. To be clear, unit density is a
// mathematical trick to use CalcSpatialInertia() to report volume and not
// a reasonable *physical* default value; 1 kg/m³ is approximately air's
// density.
SpatialInertia<double> M_GGo_G_unitDensity{SpatialInertia<double>::NaN()};
};
SpatialInertia<double> ParseInertial(XMLElement* node) {
// We use F to denote the "inertial frame" in the MujoCo documentation. B
// is the body frame.
RigidTransformd X_BF = ParseTransform(node);
double mass;
if (!ParseScalarAttribute(node, "mass", &mass)) {
Error(*node, "The inertial tag must include the mass attribute.");
return SpatialInertia<double>::NaN();
}
// We interpret the MuJoCo XML documentation as saying that if a
// diaginertia is provided, it is I_BFo_F. If a full inertia is provided,
// then it must be I_BFo_B (since the inertia is always diagonal in F).
RotationalInertia<double> I_BFo_B;
Vector3d diag;
if (ParseVectorAttribute(node, "diaginertia", &diag)) {
I_BFo_B = RotationalInertia<double>(diag[0], diag[1], diag[2])
.ReExpress(X_BF.rotation());
} else {
// fullinertia is required if diaginertia is not specified.
Vector6d full;
if (ParseVectorAttribute(node, "fullinertia", &full)) {
I_BFo_B = RotationalInertia<double>(full[0], full[1], full[2], full[3],
full[4], full[5]);
} else {
Error(*node,
"The inertial tag must include either the diaginertia or "
"fullinertia attribute.");
return SpatialInertia<double>::NaN();
}
}
SpatialInertia<double> M_BBo_B =
SpatialInertia<double>::MakeFromCentralInertia(mass, X_BF.translation(),
I_BFo_B);
return M_BBo_B;
}
struct MujocoGeometry {
RigidTransformd X_BG{};
std::string name{};
std::unique_ptr<geometry::Shape> shape{};
Vector4d rgba{.5, .5, .5, 1};
CoulombFriction<double> friction{1.0, 1.0};
SpatialInertia<double> M_GBo_B{SpatialInertia<double>::NaN()};
bool register_collision{true};
bool register_visual{true};
};
MujocoGeometry ParseGeometry(XMLElement* node, int num_geom,
bool compute_inertia,
const std::string& child_class = "") {
MujocoGeometry geom;
std::string class_name;
if (!ParseStringAttribute(node, "class", &class_name)) {
class_name = child_class.empty() ? "main" : child_class;
}
if (default_geometry_.contains(class_name)) {
// TODO(russt): Add a test case covering childclass/default nesting once
// the body element is supported.
ApplyDefaultAttributes(*default_geometry_.at(class_name), node);
}
// Per the MuJoCo documentation, the name is not part of the defaults. This
// is consistent with Drake requiring that geometry names are unique.
if (!ParseStringAttribute(node, "name", &geom.name)) {
// Use "geom#" as the default body name.
geom.name = fmt::format("geom{}", num_geom);
}
geom.X_BG = ParseTransform(node);
std::string type;
if (!ParseStringAttribute(node, "type", &type)) {
type = "sphere";
}
// Note: The documentation says e.g. for sphere "only one size parameter is
// used", but it seems that in practice often more than one are specified.
// Demanding the correct number of size parameters is too restrictive.
std::vector<double> size;
{
std::string size_attr;
ParseStringAttribute(node, "size", &size_attr);
size = ConvertToVector<double>(size_attr);
}
Vector6d fromto;
bool has_fromto = ParseVectorAttribute(node, "fromto", &fromto);
if (has_fromto) {
// Set the pose to the midpoint of the from-to vector, with the
// orientation set according to the "zaxis" specification in
// ParseTransform.
const Vector3d from = fromto.head<3>();
const Vector3d to = fromto.tail<3>();
geom.X_BG = RigidTransformd(Eigen::Quaternion<double>::FromTwoVectors(
Vector3d{0, 0, 1}, to - from),
(from + to) / 2);
} else {
geom.X_BG = ParseTransform(node);
}
std::string mesh;
bool has_mesh_attribute = ParseStringAttribute(node, "mesh", &mesh);
if (has_mesh_attribute && type != "mesh") {
if (type == "sphere" || type == "capsule" || type == "cylinder" ||
type == "ellipsoid" || type == "box") {
Error(*node,
fmt::format(
"geom {} specified type '{}' but also has a mesh attribute. "
"The intended behavior is to compute the size of the shape "
"from the mesh, but this is not supported yet (#22372).",
geom.name, type));
return geom;
} else {
Error(*node, fmt::format("geom {} specified a 'mesh', but this is not "
"allowed for type '{}'.",
geom.name, type));
return geom;
}
}
if (type == "plane") {
// We interpret the MuJoCo infinite plane as a half-space.
geom.shape = std::make_unique<geometry::HalfSpace>();
compute_inertia = false;
} else if (type == "sphere") {
if (size.size() < 1) {
// Allow zero-radius spheres (the MJCF default size is 0 0 0).
geom.shape = std::make_unique<geometry::Sphere>(0.0);
compute_inertia = false;
} else {
geom.shape = std::make_unique<geometry::Sphere>(size[0]);
}
} else if (type == "capsule") {
if (has_fromto) {
if (size.size() < 1) {
Error(*node,
"The size attribute for capsule geom using fromto must have at "
"least one element.");
return geom;
}
double length = (fromto.head<3>() - fromto.tail<3>()).norm();
geom.shape = std::make_unique<geometry::Capsule>(size[0], length);
} else {
if (size.size() < 2) {
Error(*node,
"The size attribute for capsule geom must have at least two "
"elements.");
return geom;
}
geom.shape = std::make_unique<geometry::Capsule>(size[0], 2 * size[1]);
}
} else if (type == "ellipsoid") {
if (has_fromto) {
// The specification is not properly documented in the XML schema.
Warning(*node, fmt::format("The fromto tag for ellipsoid is currently "
"unsupported; geom {} will be ignored.",
geom.name));
return geom;
} else {
if (size.size() < 3) {
Error(
*node,
"The size attribute for ellipsoid geom must have at least three "
"elements.");
return geom;
}
geom.shape =
std::make_unique<geometry::Ellipsoid>(size[0], size[1], size[2]);
}
} else if (type == "cylinder") {
if (has_fromto) {
if (size.size() < 1) {
Error(*node,
"The size attribute for cylinder geom using fromto must have "
"at least one element.");
return geom;
}
double length = (fromto.head<3>() - fromto.tail<3>()).norm();
geom.shape = std::make_unique<geometry::Cylinder>(size[0], length);
} else {
if (size.size() < 2) {
Error(*node,
"The size attribute for cylinder geom must have at least two "
"elements.");
return geom;
}
geom.shape = std::make_unique<geometry::Cylinder>(size[0], 2 * size[1]);
}
} else if (type == "box") {
if (has_fromto) {
// The specification is not properly documented in the XML schema.
Warning(*node, fmt::format("The fromto tag for box is currently "
"unsupported; geom {} will be "
"ignored.",
geom.name));
return geom;
} else {
if (size.size() < 3) {
Error(*node,
"The size attribute for box geom must have at least three "
"elements.");
return geom;
}
geom.shape = std::make_unique<geometry::Box>(
size[0] * 2.0, size[1] * 2.0, size[2] * 2.0);
}
} else if (type == "mesh") {
if (!has_mesh_attribute) {
Error(*node, fmt::format("geom {} specified type 'mesh', but did not "
"set the mesh attribute",
geom.name));
return geom;
}
if (mesh_.contains(mesh)) {
geom.shape = mesh_.at(mesh)->Clone();
} else {
Warning(
*node,
fmt::format("geom {} specified unknown mesh {} and will be ignored",
geom.name, mesh));
return geom;
}
} else if (type == "hfield") {
Warning(*node, fmt::format("The geom type '{}' is currently unsupported "
"and will be ignored.",
type));
return geom;
} else {
Error(*node, fmt::format("Unrecognized geom type {}", type));
return geom;
}
int contype{1};
int conaffinity{1};
int condim{3};
ParseScalarAttribute(node, "contype", &contype);
ParseScalarAttribute(node, "conaffinity", &conaffinity);
ParseScalarAttribute(node, "condim", &condim);
if (contype == 0 && conaffinity == 0) {
// This is a common mechanism used by MJCF authors to specify visual-only
// geometry.
geom.register_collision = false;
} else if (contype != 1 || conaffinity != 1) {
Warning(
*node,
fmt::format(
"geom {} specified contype={} and conaffinity={}; but collision "
"filter groups are not yet implemented for the mujoco parser.",
geom.name, contype, conaffinity));
}
if (condim != 3) {
// TODO(russt): Can we support condim=1 inefficiently by setting friction
// coefficients to zero? This may be insufficient given the parallel
// resistor friction coefficient logic. condim=4 or 6 are likely out of
// scope for now.
Warning(*node, fmt::format("geom {} specified condim={}, which is not "
"supported. condim=3 will be used instead.",
geom.name, condim));
}
if (geom.register_collision && type == "sphere" && size.size() < 1) {
Warning(*node,
fmt::format(
"Using zero-radius spheres (MuJoCo's default geometry) for "
"collision geometry may not be supported by all features in "
"Drake. Consider specifying a non-zero size for geom {}.",
geom.name));
}
int group{0};
ParseScalarAttribute(node, "group", &group);
if (group > 2) {
// By default, the MuJoCo visualizer does not render geom with group > 2.
// Setting the group > 2 is a common mechanism that MuJoCo uses to
// register collision-only geometry.
geom.register_visual = false;
// TODO(russt): Consider adding a <drake::enable_visual_for_group> tag so
// that mjcf authors can configure this behavior.
}
WarnUnsupportedAttribute(*node, "priority");
std::string material;
if (ParseStringAttribute(node, "material", &material)) {
if (material_.contains(material)) {
XMLElement* material_node = material_.at(material);
// Note: there are many material attributes that we do not support yet,
// nor perhaps ever. Consider warning about them here (currently, it
// seems like too much noise).
ParseVectorAttribute(material_node, "rgba", &geom.rgba);
} else {
Warning(*node,
fmt::format("geom {} specified an unrecognized material {}",
geom.name, material));
}
}
// rgba takes precedence over materials, so must be parsed after.
ParseVectorAttribute(node, "rgba", &geom.rgba);
// Note: The documentation suggests that at least 3 friction parameters
// should be specified. But humanoid_CMU.xml in the DeepMind suite
// specifies only one, and in fact we only need one.
std::vector<double> friction;
{
std::string friction_attr;
ParseStringAttribute(node, "friction", &friction_attr);
friction = ConvertToVector<double>(friction_attr);
}
if (!friction.empty()) {
// MuJoCo's friction specification is [sliding, torsional, rolling]. We
// set the static and dynamic friction to `sliding`, and do not support
// the other parameters.
geom.friction = CoulombFriction(friction[0], friction[0]);
if ((friction.size() > 1 && friction[1] != 0.0) ||
(friction.size() > 2 && friction[2] != 0.0)) {
Warning(
*node,
fmt::format(
"The torsional and rolling friction specified in the friction "
"attribute of {} are unsupported and will be ignored.",
node->Name()));
}
}
WarnUnsupportedAttribute(*node, "solmix");
WarnUnsupportedAttribute(*node, "solref");
WarnUnsupportedAttribute(*node, "solimp");
WarnUnsupportedAttribute(*node, "margin");
WarnUnsupportedAttribute(*node, "gap");
WarnUnsupportedAttribute(*node, "fitscale");
WarnUnsupportedAttribute(*node, "user");
if (compute_inertia) {
auto policy = diagnostic_.MakePolicyForNode(node);
InertiaCalculator calculator(policy, mesh, &mesh_inertia_);
const auto [volume, p_GoGcm_G, G_GGo_G] = calculator.Calc(*geom.shape);
if (calculator.used_convex_hull_fallback()) {
// When the Mujoco parser falls back to using a convex hull, it prints
// a warning. We ape that behavior to provide a similar experience.
//
// N.B. Mujoco falls back only if the mesh reported a negative volume.
// SpatialInertia::IsPhysicallyValid() will also fail in that case. But
// fails in other cases (e.g., positive mass but negative inertia) where
// Drake will fallback and Mujoco won't. Such a mesh would be rare.
// Generally, we expect Drake and Mujoco to agree on real world meshes.
Warning(
*node,
fmt::format("CalcSpatialInertia() failed to compute a physically "
"valid inertia for mesh {} (probably the mesh is not "
"watertight). The spatial inertia was computed using "
"its convex hull as a fallback.",
mesh));
}
double mass{};
if (!ParseScalarAttribute(node, "mass", &mass)) {
double density{1000}; /* fallback default ≈ water density */
ParseScalarAttribute(node, "density", &density);
mass = volume * density;
}
SpatialInertia<double> M_GGo_G(mass, p_GoGcm_G, G_GGo_G,
/*skip_validity_check=*/true);
if (!M_GGo_G.IsPhysicallyValid()) {
Error(*node, fmt::format("geom {} {}", geom.name,
M_GGo_G.CriticizeNotPhysicallyValid()));
return geom;