Drake
Drake C++ Documentation
EdgeMeasure Class Reference

Detailed Description

The measure of the distance of the edge from q1 to q2 and the portion of that is collision free.

Distance is that produced by CollisionChecker::ComputeConfigurationDistance() for the entire edge between q1 and q2.

The portion of the edge between q1 and q2 that is collision free is encoded as the value α with the following semantics:

  • α = 1: No collisions were detected. The full edge can be considered collision free. This is the only time completely_free() reports true.
  • 0 ≤ α < 1: A collision was detected between q1 and q2. α is the largest interpolation value such that an edge from q1 to qα can be considered collision free (where qα = interpolate(q1, q2, α)). partially_free() reports true.
  • α is undefined: q1 was found to be in collision. That means there exists no α for which the edge (q1, qα) can be collision free.
Note
The length of the collision-free edge can be computed via distance * α. To simplify comparisons between a number of edges, some of which may not have a defined α, the function alpha_or(default_value) is provided. This is equivalent to edge.partially_free() ? edge.alpha() : default_value.
For α to be meaningful, the caller is obliged to make sure that they use the same interpolating function as the CollisionChecker did when generating the measure. Calling CollisionChecker::InterpolateBetweenConfigurations() on the same checker instance would satisfy that requirement.

#include <drake/planning/edge_measure.h>

Public Member Functions

 EdgeMeasure (double distance, double alpha)
 
bool completely_free () const
 Reports true if all samples were collision free. More...
 
bool partially_free () const
 Reports true if there's any portion of the edge (starting from q1) that is collision free. More...
 
double distance () const
 Returns the edge distance. More...
 
double alpha () const
 Returns the value of alpha, if defined. More...
 
double alpha_or (double default_value) const
 Returns the value of alpha, if defined, or the provided default value. More...
 
Implements CopyConstructible, CopyAssignable, MoveConstructible, MoveAssignable
 EdgeMeasure (const EdgeMeasure &)=default
 
EdgeMeasureoperator= (const EdgeMeasure &)=default
 
 EdgeMeasure (EdgeMeasure &&)=default
 
EdgeMeasureoperator= (EdgeMeasure &&)=default
 

Constructor & Destructor Documentation

◆ EdgeMeasure() [1/3]

EdgeMeasure ( const EdgeMeasure )
default

◆ EdgeMeasure() [2/3]

EdgeMeasure ( EdgeMeasure &&  )
default

◆ EdgeMeasure() [3/3]

EdgeMeasure ( double  distance,
double  alpha 
)
Precondition
0 ≤ distance
0 ≤ alpha ≤ 1 to indicate defined alpha, negative otherwise.

Member Function Documentation

◆ alpha()

double alpha ( ) const

Returns the value of alpha, if defined.

Note: Due to the sampling nature of the edge check, the edge (q1, qα) may not actually be collision free (due to a missed collision). There's a further subtlety. Subsequently calling CheckEdgeCollisionFree(q1, qα) may return false. This apparent contradiction is due to the fact that the samples on the edge (q1, qα) will not necessarily be the same as the samples originally tested on the edge (q1, q2). It is possible for those new samples to detect a previously missed collision. This is not a bug, merely a property of sampling-based testing.

Precondition
partially_free() returns true.

◆ alpha_or()

double alpha_or ( double  default_value) const

Returns the value of alpha, if defined, or the provided default value.

◆ completely_free()

bool completely_free ( ) const

Reports true if all samples were collision free.

◆ distance()

double distance ( ) const

Returns the edge distance.

◆ operator=() [1/2]

EdgeMeasure& operator= ( EdgeMeasure &&  )
default

◆ operator=() [2/2]

EdgeMeasure& operator= ( const EdgeMeasure )
default

◆ partially_free()

bool partially_free ( ) const

Reports true if there's any portion of the edge (starting from q1) that is collision free.

By implication, if completely_free() reports true, so will this.


The documentation for this class was generated from the following file: