Measure allowing to compute the 3d shape normal orientation (phi component of the (phi, theta) representation) from the second order moment matrix computed from the Inertia3d measurement.

This measure computes the normal orientation value in the x-y plane of the inertia matrix calculated for each 3D shape, without taking the voxels intensities into account, and returns the phi component, expressed in radians.

To avoid redundancies in the orienation representation, the measure ensure that for a couple of angles ( $\phi$ , $\theta$ ), $\theta \in [0, \pi/2]$ . $\phi$ is hence adjusted by rotating to $\pi$ if the initial value of $\theta > \pi/2$ .

This orientation is calculated from the eigen vector related to the minimum eignen value.

Typically, this measure is usefull to determinate the orientation of a flat disk, for which the orientation inside the disk plane is not relevant.

Here is an example of phi orientation measurement :

Measure allowing to compute the 3d shape normal orientation (phi component of the (phi, theta) representation) from the second order moment matrix computed from the Inertia3d measurement

Measure synthesis :

Measure Type	Measure Unit Type	Parameter Type	Result Type	Shape Requirements
Generic	Angle	None	Value (ipsdk::ipReal64)	Row Intersections

See Shape measurement for additional information on these pictograms

Example of Python code :

Generic example in 3d case :

import PyIPSDK

import PyIPSDK.IPSDKIPLShapeAnalysis as shapeanalysis

    # Create the infoset
    inMeasureInfoSet3d = PyIPSDK.createMeasureInfoSet3d()
    PyIPSDK.createMeasureInfo(inMeasureInfoSet3d, "Inertia3dNormalOrientationPhiMsr")
    
    #Perform the analysis
    outMeasureSet = shapeanalysis.labelAnalysis3d(inGreyImg, inLabelImg, inMeasureInfoSet3d)
    
    # save results to csv format
    PyIPSDK.saveCsvMeasureFile(os.path.join(tmpPath,  "shape_analysis_results.csv"), outMeasureSet)
    
    # retrieve measure results
    outMsr = outMeasureSet.getMeasure("Inertia3dNormalOrientationPhiMsr")
    
    # retrieve measure values
    outMsrValues = outMsr.getMeasureResult().getColl(0)
    print("First label measurement equal " + str(outMsrValues[1]))

Example of C++ code :

Example informations

Associated library

IPSDKIPLShapeAnalysis

Code Example

    // define a measure info set
    MeasureInfoSetPtr pMeasureInfoSet = MeasureInfoSet::create3dInstance();
    createMeasureInfo(pMeasureInfoSet, "Inertia3dNormalOrientationPhiMsr");
    // compute measure
    MeasureSetPtr pOutMeasureSet = labelAnalysis3d(pLabelImg, pLabelImg, pMeasureInfoSet);
    // retrieve associated results
    const MeasureConstPtr& pOutMsr = pOutMeasureSet->getMeasure("Inertia3dNormalOrientationPhiMsr");
    const ipsdk::shape::analysis::ValueMeasureResult<ipsdk::ipReal64>& outResults = static_cast<const ipsdk::shape::analysis::ValueMeasureResult<ipsdk::ipReal64>&>(pOutMsr->getMeasureResult());