SmartProjectionParams

SmartProjectionParams is a structure used to configure the behavior of “smart” factors like SmartProjectionFactor, SmartProjectionPoseFactor, and SmartStereoFactor. These factors implicitly manage the triangulation of a 3D point observed by multiple cameras.

Parameters include:

linearizationMode: Determines the type of linear factor produced when .linearize() is called.
- HESSIAN (Default): Creates a RegularHessianFactor by marginalizing out the point.
- IMPLICIT_SCHUR: Creates a RegularImplicitSchurFactor.
- JACOBIAN_Q: Creates a JacobianFactorQ.
- JACOBIAN_SVD: Creates a JacobianFactorSVD.
degeneracyMode: How to handle cases where triangulation fails or is ill-conditioned.
- IGNORE_DEGENERACY (Default): Factor might become ill-conditioned.
- ZERO_ON_DEGENERACY: Return a zero-information factor (Hessian/Jacobian) if triangulation fails.
- HANDLE_INFINITY: Treat the point as being at infinity (uses Unit3 representation).
triangulation: A gtsam.TriangulationParameters struct containing parameters for the triangulateSafe function:
- rankTolerance: Rank tolerance threshold for SVD during triangulation.
- enableEPI: Use Essential matrix check for epipolar inconsistency (only for Point3 landmarks).
- landmarkDistanceThreshold: If point distance is greater than this, use point-at-infinity.
- dynamicOutlierRejectionThreshold: If non-zero, dynamically rejects measurements based on reprojection error (threshold in sigmas).
retriangulationThreshold: If the change in camera poses between linearizations exceeds this threshold (Frobenius norm difference), the point is re-triangulated.
throwCheirality / verboseCheirality: Flags inherited from projection factors to control exception handling when a point is behind a camera.

import gtsam
from gtsam import SmartProjectionParams, LinearizationMode, DegeneracyMode

Creating and Modifying Params¶

# Default parameters
default_params = SmartProjectionParams()
print("Default Parameters:")
default_params.print()

# Custom parameters
custom_params = SmartProjectionParams(
    linMode = LinearizationMode.JACOBIAN_Q,
    degMode = DegeneracyMode.ZERO_ON_DEGENERACY,
    throwCheirality = False,
    verboseCheirality = True,
    retriangulationTh = 1e-3
)
# Modify triangulation parameters directly
custom_params.setRankTolerance(1e-8)
custom_params.setEnableEPI(False)
custom_params.setDynamicOutlierRejectionThreshold(3.0) # Reject points with reproj error > 3*sigma

print("\nCustom Parameters:")
custom_params.print()

Default Parameters:
linearizationMode: 0
   degeneracyMode: 0
rankTolerance = 1
enableEPI = 0
landmarkDistanceThreshold = -1
dynamicOutlierRejectionThreshold = -1
useLOST = 0
noise model


Custom Parameters:
linearizationMode: 2
   degeneracyMode: 1
rankTolerance = 1e-08
enableEPI = 0
landmarkDistanceThreshold = -1
dynamicOutlierRejectionThreshold = 1
useLOST = 0
noise model

Usage¶

These SmartProjectionParams objects are passed to the constructors of smart factors, like SmartProjectionPoseFactor.

from gtsam import SmartProjectionPoseFactorCal3_S2, Cal3_S2

# Example: Using custom params with a smart factor
noise = gtsam.noiseModel.Isotropic.Sigma(2, 1.0)
K = Cal3_S2(500, 500, 0, 320, 240)

smart_factor = SmartProjectionPoseFactorCal3_S2(noise, K, custom_params)
print("Smart Factor created with custom params:")
smart_factor.print()

Smart Factor created with custom params:
SmartProjectionPoseFactor, z = 
 SmartProjectionFactor
linearizationMode: 2
triangulationParameters:
rankTolerance = 1e-08
enableEPI = 0
landmarkDistanceThreshold = -1
dynamicOutlierRejectionThreshold = 1
useLOST = 0
noise model

result:
no point, status = 1

SmartFactorBase, z = 
  keys = { }