Tectonic Puzzle

Pipeline description

This example processes a two-dimensional geophysics model of the Earth surface to segment it according to the tectonic plates.

The outer surface of the data-set is first extracted with a combination of ParaView's Connectivity and Threshold. Then, the log10 of the Viscosity scalar field is computed with a Calculator (bottom-right view on the above screenshot).

Several passes of topological simplification are then combined, using PersistenceDiagram, TopologicalSimplification and MorseSmaleComplex to further clean the scalar field. The Persistence Diagram of the scalar field at the end of this cleaning step is represented in the bottom-right view on the above screenshot.

Once this is done, since the low values of the scalar field represent the plates borders and the regions of high values the plates themselves, the Descending 1-Separatrices of the Morse-Smale Complex follow the plates borders and the AscendingManifold Segmentation of the Morse-Smale Complex gives us the expected segmentation of the tectonic plates (top-right view on the above screenshot).

Finally, the IdentifierRandomizer filter is used to color neighbor cells with a distinct color (top right view on the above screenshot).

ParaView

To reproduce the above screenshot, go to your ttk-data directory and enter the following command:

paraview states/tectonicPuzzle.pvsm

Python code

#!/usr/bin/env python

from paraview.simple import *

# create a new 'XML Unstructured Grid Reader'
tectonicPuzzlevtu = XMLUnstructuredGridReader(FileName=["tectonicPuzzle.vtu"])

# create a new 'Extract Surface'
extractSurface1 = ExtractSurface(Input=tectonicPuzzlevtu)

# create a new 'Clean to Grid'
cleantoGrid1 = CleantoGrid(Input=extractSurface1)

# create a new 'Tetrahedralize'
tetrahedralize1 = Tetrahedralize(Input=cleantoGrid1)

# create a new 'Connectivity'
connectivity1 = Connectivity(Input=tetrahedralize1)

# create a new 'Threshold'
threshold1 = Threshold(Input=connectivity1)
threshold1.Scalars = ["POINTS", "RegionId"]
threshold1.ThresholdMethod = "Between"
threshold1.LowerThreshold = 1.0
threshold1.UpperThreshold = 1.0

# create a new 'Calculator'
calculator1 = Calculator(Input=threshold1)
calculator1.ResultArrayName = "logViscosity"
calculator1.Function = "log10(Viscosity)"

# create a new 'TTK PersistenceDiagram'
tTKPersistenceDiagram1 = TTKPersistenceDiagram(Input=calculator1)
tTKPersistenceDiagram1.ScalarField = ["POINTS", "logViscosity"]

# create a new 'Threshold'
threshold2 = Threshold(Input=tTKPersistenceDiagram1)
threshold2.Scalars = ["CELLS", "PairIdentifier"]
threshold2.ThresholdMethod = "Between"
threshold2.LowerThreshold = -0.1
threshold2.UpperThreshold = 999999999

# create a new 'Threshold'
persistenceThreshold = Threshold(Input=threshold2)
persistenceThreshold.Scalars = ["CELLS", "Persistence"]
persistenceThreshold.ThresholdMethod = "Between"
persistenceThreshold.LowerThreshold = 0.5
persistenceThreshold.UpperThreshold = 999999999

# create a new 'TTK IcospheresFromPoints'
tTKIcospheresFromPoints1 = TTKIcospheresFromPoints(Input=persistenceThreshold)
tTKIcospheresFromPoints1.Radius = 0.5

# create a new 'TTK TopologicalSimplification'
tTKTopologicalSimplification1 = TTKTopologicalSimplification(
    Domain=calculator1, Constraints=persistenceThreshold
)
tTKTopologicalSimplification1.ScalarField = ["POINTS", "logViscosity"]

# create a new 'TTK MorseSmaleComplex'
tTKMorseSmaleComplex1 = TTKMorseSmaleComplex(Input=tTKTopologicalSimplification1)
tTKMorseSmaleComplex1.ScalarField = ["POINTS", "logViscosity"]

# create a new 'TTK IcospheresFromPoints'
tTKIcospheresFromPoints2 = TTKIcospheresFromPoints(Input=tTKMorseSmaleComplex1)
tTKIcospheresFromPoints2.Radius = 0.1

# create a new 'Threshold'
threshold3 = Threshold(Input=tTKIcospheresFromPoints2)
threshold3.Scalars = ["POINTS", "CellDimension"]
threshold3.ThresholdMethod = "Between"
threshold3.LowerThreshold = 2.0
threshold3.UpperThreshold = 2.0

# create a new 'Threshold'
lARGE_MAXIMA_THRESHOLD = Threshold(Input=threshold3)
lARGE_MAXIMA_THRESHOLD.Scalars = ["POINTS", "ManifoldSize"]
lARGE_MAXIMA_THRESHOLD.ThresholdMethod = "Between"
lARGE_MAXIMA_THRESHOLD.LowerThreshold = 75.0
lARGE_MAXIMA_THRESHOLD.UpperThreshold = 999999999

# create a new 'Threshold'
pERSISTENT_MINIMA = Threshold(Input=tTKIcospheresFromPoints1)
pERSISTENT_MINIMA.Scalars = ["POINTS", "CriticalType"]

# create a new 'Append Datasets'
pERSISTENT_MINIMA_AND_LARGE_MAXIMA = AppendDatasets(
    Input=[pERSISTENT_MINIMA, lARGE_MAXIMA_THRESHOLD]
)

# create a new 'TTK TopologicalSimplification'
tTKTopologicalSimplification2 = TTKTopologicalSimplification(
    Domain=tTKTopologicalSimplification1, Constraints=pERSISTENT_MINIMA_AND_LARGE_MAXIMA
)
tTKTopologicalSimplification2.ScalarField = ["POINTS", "logViscosity"]

# create a new 'TTK PersistenceDiagram'
tTKPersistenceDiagram2 = TTKPersistenceDiagram(Input=tTKTopologicalSimplification2)
tTKPersistenceDiagram2.ScalarField = ["POINTS", "logViscosity"]

# create a new 'Threshold'
threshold4 = Threshold(Input=tTKPersistenceDiagram2)
threshold4.Scalars = ["CELLS", "PairIdentifier"]
threshold4.ThresholdMethod = "Between"
threshold4.LowerThreshold = -0.1
threshold4.UpperThreshold = 999999999

# create a new 'Threshold'
threshold5 = Threshold(Input=threshold4)
threshold5.Scalars = ["CELLS", "PairType"]
threshold5.ThresholdMethod = "Between"
threshold5.LowerThreshold = 1.0
threshold5.UpperThreshold = 1.0

# create a new 'Calculator'
calculator2 = Calculator(Input=threshold5)
calculator2.ResultArrayName = "SaddleValue"
calculator2.Function = "coordsX"

# create a new 'Threshold'
sADDLE_VALUE_THRESHOLD = Threshold(Input=calculator2)
sADDLE_VALUE_THRESHOLD.Scalars = ["POINTS", "SaddleValue"]
sADDLE_VALUE_THRESHOLD.ThresholdMethod = "Between"
sADDLE_VALUE_THRESHOLD.LowerThreshold = -0.2
sADDLE_VALUE_THRESHOLD.UpperThreshold = 1.75

# create a new 'TTK IcospheresFromPoints'
tTKIcospheresFromPoints3 = TTKIcospheresFromPoints(Input=sADDLE_VALUE_THRESHOLD)
tTKIcospheresFromPoints3.Radius = 0.5

# create a new 'Threshold'
lARGE_MAXIMA_LOW_SADDLE = Threshold(Input=tTKIcospheresFromPoints3)
lARGE_MAXIMA_LOW_SADDLE.Scalars = ["POINTS", "CriticalType"]
lARGE_MAXIMA_LOW_SADDLE.ThresholdMethod = "Between"
lARGE_MAXIMA_LOW_SADDLE.LowerThreshold = 3.0
lARGE_MAXIMA_LOW_SADDLE.UpperThreshold = 3.0

# create a new 'Append Datasets'
lARGE_MAXIMA_LOW_SADDLE_AND_PERSISTENT_MINIMA = AppendDatasets(
    Input=[pERSISTENT_MINIMA, lARGE_MAXIMA_LOW_SADDLE]
)

# create a new 'TTK TopologicalSimplification'
tTKTopologicalSimplification3 = TTKTopologicalSimplification(
    Domain=tTKTopologicalSimplification2,
    Constraints=lARGE_MAXIMA_LOW_SADDLE_AND_PERSISTENT_MINIMA,
)
tTKTopologicalSimplification3.ScalarField = ["POINTS", "logViscosity"]

# create a new 'TTK MorseSmaleComplex'
tTKMorseSmaleComplex2 = TTKMorseSmaleComplex(Input=tTKTopologicalSimplification3)
tTKMorseSmaleComplex2.ScalarField = ["POINTS", "logViscosity"]

# create a new 'TTK IdentifierRandomizer'
tTKIdentifierRandomizer1 = TTKIdentifierRandomizer(
    Input=OutputPort(tTKMorseSmaleComplex2, 3)
)
tTKIdentifierRandomizer1.ScalarField = ["POINTS", "AscendingManifold"]

SaveData("Segmentation.vtu", tTKIdentifierRandomizer1)

To run the above Python script, go to your ttk-data directory and enter the following command:

pvpython python/tectonicPuzzle.py

Inputs

• tectonicPuzzle.vtu: two 2-dimensional spheres (one around the other) made up of a triangular mesh. There are several point data arrays attached to it. Those scalar fields represent geophysics measures on the earth surface (and at a certain depth under it); only the Viscosity field will be used in the current example.

Outputs

• Segmentation.vtu: the output segmentation in VTK file format (top right view, above screenshot). This corresponds to a segmentation of the tectonic plates from the Viscosity scalar field.

C++/Python API

IcospheresFromPoints

IdentifierRandomizer

MorseSmaleComplex

PersistenceDiagram

TopologicalSimplification