Configuring transforms

This page describes how to use classes such as schema::Rotation and schema::Transform to denote stochastic quantities, as a bridge between loading a scenario specification and populating the corresponding math::RigidTransform quantities.

The broader concepts are discussed at Configuring distributions. Here, we cover details related to rotations and transforms in particular.

We'll explain uses of schema::Rotation and schema::Transform using their matching YAML syntax as parsed by yaml::LoadYamlFile.

Rotations

This shows the syntax for a schema::Rotation.

When no details are given, the default rotation is the identity matrix:

rotation: {}

For clarity, you may also specify Identity variant tag explicitly. This version and the above version have exactly the same effect:

rotation: !Identity {}

To specify roll, pitch, yaw angles using math::RollPitchYaw conventions, use Rpy as the variant tag:

rotation: !Rpy
  deg: [10.0, 20.0, 30.0]

To specify a rotation angle and axis in the sense of Eigen::AngleAxis, use AngleAxis as the variant tag:

rotation: !AngleAxis
  angle_deg: 10.0
  axis: [0.0, 1.0, 0.0]

You may also use YAML's flow style to fit everything onto a single line. These one-line spellings are the equivalent to those above.

rotation: !Rpy { deg: [10.0, 20.0, 30.0] }

rotation: !AngleAxis { angle_deg: 10.0, axis: [0.0, 1.0, 0.0] }

Stochastic Rotations

To specify a stochastic rotation sampled from a uniform distribution over SO(3):

rotation: !Uniform {}

The other available representations also accept stochastic distributions for their values:

rotation: !Rpy
  deg: !UniformVector
    min: [ 0.0, 10.0, 20.0]
    max: [30.0, 40.0, 50.0]

Or:

rotation: !AngleAxis
  angle_deg: !Uniform
    min: 8.0
    max: 10.0
  axis: !UniformVector
    min: [0.0, 0.9, 0.0]
    max: [0.1, 1.0, 0.0]

For an explanation of !Uniform, !UniformVector, and other available options (Gaussian, etc.) for scalar and vector quantities, see Configuring distributions.

Transforms

This shows the syntax for a schema::Transform. A transform is merely a translation and rotation, optionally with a some given string as a base_frame.

transform:
  translation: [1.0, 2.0, 3.0]
  rotation: !Rpy { deg: [10.0, 20.0, 30.0] }

Or:

transform:
  base_frame: foo
  translation: [0.0, 0.0, 1.0]
  rotation: !Identity {}

Stochastic Transforms

Either or both of the rotational or translation component can be stochastic:

transform:
  translation: !UniformVector
    min: [-1.0, -1.0, -1.0]
    max: [ 1.0,  1.0,  1.0]
  rotation: !Uniform {}

For an explanation of !Uniform, !UniformVector, and other available options (Gaussian, etc.) for scalar and vector quantities, see Configuring distributions.