template<class Id, class KinematicsValue>
class drake::geometry::KinematicsVector< Id, KinematicsValue >
A KinematicsVector is a container class used to report kinematics data for registered frames and geometries (keyed by unique FrameId/GeometryId values) to SceneGraph where the set of keys (FrameId/GeometryId) is usually constant and the values (kinematics data) are varying.
It is an internal class and one should never interact with it directly. The template aliases FramePoseVector and GeometryConfigurationVector that instantiate KinematicsVector should be used instead.
template <typename T>
class MySystem : public LeafSystem<T> {
public:
MySystem() {
...
this->DeclareAbstractOutputPort(
&AllocInConstructorSystem::CalcFramePoseOutput);
...
}
private:
void CalcFramePoseOutput(const Context<T>& context,
geometry::FramePoseVector<T>* poses) const {
poses->clear();
for (int i = 0; i < static_cast<int>(frame_ids_.size()); ++i) {
poses->set_value(frame_ids_[i], poses_[i]);
}
}
std::vector<FrameId> frame_ids_;
std::vector<RigidTransform<T>> poses_;
};
If a System only ever emits a single frame/geometry (or small-constant-number of frames/geometries), then there's a shorter alternative way to write a Calc method, using an initializer_list:
void CalcFramePoseOutput(const Context<T>& context,
geometry::FramePoseVector<T>* poses) const {
const RigidTransform<T>& pose = ...;
*poses = {{frame_id_, pose}};
}
N.B. When the systems framework calls the Calc method, the value pointed to by poses is in an unspecified state. The implementation of Calc must always ensure that poses contains the correct value upon return, no matter what value it started with. The easy ways to do this are to call either poses->clear() or the assignment operator *poses = ....
- Template Parameters
-
| Id | The key used to locate the kinematics data. Can be FrameId or GeometryId. |
| KinematicsValue | The underlying data type of the kinematics data (e.g., pose, configuration, or velocity). |
The FramePoseVector and GeometryConfigurationVector classes are aliases of the KinematicsVector instantiated on specific data types (RigidTransform and VectorX respectively). Each of these data types are templated on Eigen scalars. All supported combinations of data type and scalar type are already available to link against in the containing library. No other values for KinematicsValue are supported.
Currently, the following data types with the following scalar types are supported:
| Alias | Instantiation | Scalar types |
| FramePoseVector<Scalar> | KinematicsVector<FrameId,RigidTransform<Scalar>> | double/AutoDiffXd/Expression |
| GeometryConfigurationVector<Scalar> | KinematicsVector<GeometryId, VectorX<Scalar>> | double/AutoDiffXd/Expression |
