Available Variables/Factors

## Variables in Caesar.jl

You can check for the latest variable types by running the following in your terminal:

``````using RoME, Caesar
subtypes(IncrementalInference.InferenceVariable)
IncrementalInference.getCurrentWorkspaceVariables()``````

Default variables in IncrementalInference

``struct ContinuousScalar <: InferenceVariable``

Most basic continuous scalar variable a `::FactorGraph` object.

``struct ContinuousMultivariate{T1<:Tuple} <: InferenceVariable``

Continuous variable of dimension `.dims` on manifold `.manifolds`.

### 2D Variables

The current variables types are:

Missing docstring.

Missing docstring for `Polar`. Check Documenter's build log for details.

``struct Point2 <: InferenceVariable``

XY Euclidean manifold variable node softtype.

``struct Pose2 <: InferenceVariable``

Pose2 is a SE(2) mechanization of two Euclidean translations and one Circular rotation, used for general 2D SLAM.

``mutable struct DynPoint2 <: InferenceVariable``

Dynamic point in 2D space with velocity components: `x, y, dx/dt, dy/dt`

``mutable struct DynPose2 <: InferenceVariable``

Dynamic pose variable with velocity components: `x, y, theta, dx/dt, dy/dt`

### 3D Variables

``struct Point3 <: InferenceVariable``

XYZ Euclidean manifold variable node softtype.

Example

``p3 = Point3()``
``struct Pose3 <: InferenceVariable``

Pose3 is currently a Euler angle mechanization of three Euclidean translations and three Circular rotation.

Future:

• Work in progress on AMP3D for proper non-Euler angle on-manifold operations.
``mutable struct InertialPose3 <: FunctorPairwise``

Inertial Odometry version of preintegration procedure and used as a factor between InertialPose3 types for inertial navigation in factor graphs.

Note Please open an issue with JuliaRobotics/RoME.jl for specific requests, problems, or suggestions. Contributions are also welcome.

Note There might be more variable types in Caesar/RoME/IIF not yet documented here.

## Factors in Caesar.jl

You can check for the latest factor types by running the following in your terminal:

``````using RoME, Caesar
println("- Singletons (priors): ")
println.(sort(string.(subtypes(IncrementalInference.FunctorSingleton))));
println("- Pairwise (variable constraints): ")
println.(sort(string.(subtypes(IncrementalInference.FunctorPairwise))));
println("- Pairwise (variable minimization constraints): ")
println.(sort(string.(subtypes(IncrementalInference.FunctorPairwiseMinimize))));``````

### Priors (Absolute Data)

Existing prior (unary) factors in Caesar.jl/RoME.jl/IIF.jl include:

``mutable struct PriorPolar{T1<:Union{AliasingScalarSampler, BallTreeDensity, Distribution}, T2<:Union{AliasingScalarSampler, BallTreeDensity, Distribution}} <: FunctorSingleton``

Prior belief on any Polar related variable.

``mutable struct PriorPoint2{T} <: FunctorSingleton``

Direction observation information of a `Point2` variable.

``mutable struct PriorPose2{T} <: FunctorSingleton``

Introduce direct observations on all dimensions of a Pose2 variable:

Example:

``PriorPose2( MvNormal([10; 10; pi/6.0], Matrix(Diagonal([0.1;0.1;0.05].^2))) )``

### Prior 3D (unary) factors

``mutable struct PriorPoint3{T} <: FunctorSingleton``

Direction observation information of a `Point3` variable.

``mutable struct PriorPose3 <: FunctorSingleton``

Direct observation information of `Pose3` variable type.

Defaults in IncrementalInference.jl:

``struct Prior{T} <: FunctorSingleton``

Default prior on all dimensions of a variable node in the factor graph. `Prior` is not recommended when non-Euclidean dimensions are used in variables.

``struct PartialPrior{T, P} <: FunctorSingleton``

Partial prior belief (absolute data) on any variable, given `<:SamplableBelief` and which dimensions of the intended variable.

``struct MixturePrior{T} <: FunctorSingleton``

Define a categorical mixture of prior beliefs on a variable.

### Conditional Likelihoods (Relative Data)

Existing n-ary factors in Caesar.jl/RoME.jl/IIF.jl include:

``mutable struct PolarPolar{T1<:Union{AliasingScalarSampler, BallTreeDensity, Distribution}, T2<:Union{AliasingScalarSampler, BallTreeDensity, Distribution}} <: FunctorPairwise``

Linear offset factor of `IIF.SamplableBelief` between two `Polar` variables.

``mutable struct Point2Point2{D<:Union{AliasingScalarSampler, BallTreeDensity, Distribution}} <: FunctorPairwise``
``mutable struct Point2Point2WorldBearing{T} <: FunctorPairwise``
``mutable struct Pose2Point2Bearing{B<:Union{AliasingScalarSampler, BallTreeDensity, Distribution}} <: FunctorPairwiseMinimize``

Single dimension bearing constraint from Pose2 to Point2 variable.

``mutable struct Pose2Point2BearingRange{B<:Union{AliasingScalarSampler, BallTreeDensity, Distribution}, R<:Union{AliasingScalarSampler, BallTreeDensity, Distribution}} <: FunctorPairwiseMinimize``

Bearing and Range constraint from a Pose2 to Point2 variable.

``mutable struct Pose2Point2Range{T} <: FunctorPairwise``

Range only measurement from Pose2 to Point2 variable.

``mutable struct Pose2Pose2{T} <: FunctorPairwise``
``mutable struct DynPoint2VelocityPrior{T} <: FunctorSingleton``
``mutable struct DynPoint2DynPoint2{T} <: FunctorPairwise``
``mutable struct VelPoint2VelPoint2{T} <: FunctorPairwiseMinimize``
``mutable struct Point2Point2Velocity{T} <: FunctorPairwiseMinimize``
``mutable struct DynPose2VelocityPrior{T1, T2} <: FunctorSingleton``
``mutable struct VelPose2VelPose2{T1, T2} <: FunctorPairwiseMinimize``
``mutable struct DynPose2Pose2{T} <: FunctorPairwise``
``mutable struct Pose3Pose3 <: FunctorPairwise``

Rigid transform factor between two Pose3 compliant variables.

Missing docstring.

Missing docstring for `InertialPose3`. Check Documenter's build log for details.

``mutable struct PriorPose3ZRP{T1, T2} <: FunctorSingleton``

Partial prior belief on Z, Roll, and Pitch of a `Pose3`.

``mutable struct PartialPriorRollPitchZ{T1, T2} <: FunctorSingleton``

Partial prior belief on Roll Pitch and Z of a `Pose3` variable.

``mutable struct PartialPose3XYYaw{T1, T2} <: FunctorPairwise``

Partial factor between XY and Yaw of two Pose3 variables.

To be deprecated: use Pose3Pose3XYYaw instead.

``mutable struct Pose3Pose3XYYaw{T1, T2} <: FunctorPairwise``

Partial factor between XY and Yaw of two Pose3 variables.

Defaults in IncrementalInference.jl:

``struct LinearConditional{T} <: FunctorPairwise``

Default linear offset between two scalar variables.

``struct MixtureLinearConditional{T} <: FunctorPairwise``

Define a categorical mixture of (relative) likelihood beliefs between any two variables.

## Extending Caesar with New Variables and Factors

A question that frequently arises is how to design custom variables and factors to solve a specific type of graph. One strength of Caesar is the ability to incorporate new variables and factors at will. Please refer to Adding Factors for more information on creating your own factors.