Editing IVAJ/Level1 (section)

==<span id="Sidebar">Sidebar:</span> <font color="#0000DD">SwitchCoord Python Module</font>==
Here we present a complete listing of the python code from our customized <font face="Courier">SwitchCoord</font> program module.  At the beginning of the "Physics Analysis" segment of the code, we assign names to the data arrays that have been acquired as input from <font face="Courier">vtkPLOT3DReader</font>: ''<font face="Courier">pcoords</font>'' is a tuple that identifies the Cartesian-based coordinate location of each grid vertex, ''<font face="Courier">density</font>'' is a scalar that specifies the mass density, and ''<font face="Courier">momentum</font>'' is a tuple that specifies the values of the cylindrical-coordinate-based vector momentum at each grid vertex.  We detail the remaining logic of the physics analysis in the main text.

<pre>
import core.modules.module_registry
from core.modules.vistrails_module import Module, ModuleError
import vtk, math
version="0.0.0"
name="SwitchCoord"
identifier="edu.lsu.switchcoord"

class SwitchCoord(Module):
    def compute(self):
        minp = self.getInputFromPort("min_density")
        Domega = self.getInputFromPort("Domega")
        dataset=self.getInputFromPort("dataset")
        output = self.create_instance_of_type('edu.utah.sci.vistrails.vtk', 'vtkStructuredGrid')
        output.vtkInstance = vtk.vtkStructuredGrid()
        mydata=output.vtkInstance
        mydata.DeepCopy(dataset.vtkInstance)
        self.op(mydata, minp, omega)
        self.setResult("changed_dataset", output)

    ###################################
    ##
    ## Begin:  Physics Analysis
    ##
    ###################################

    def op(self, mydata, minp, omega):
        extent=mydata.GetExtent()
        pcoords = mydata.GetPoints().GetData()
        density = mydata.GetPointData().GetScalars("Density")
        momentum = mydata.GetPointData().GetVectors("Momentum")

        maxnorm = 0.0
        for i in range(0, mydata.GetNumberOfPoints()):
            [x, y, z] = pcoords.GetTuple3(i)  
            [_v1, _v2, _v3] = momentum.GetTuple3(i)
            p = density.GetValue(i)
            r = math.sqrt(x*x + y*y)         
            phi = math.atan2(y, x)
            if p < minp: 
                vx=vy=vz=0
            else:
                vr = _v1 / p
                vphi = _v2 / (p) + r * omega
                vz = _v3 / p
                vx = vr * math.cos(phi) - vphi * math.sin(phi)
                vy = vr * math.sin(phi) + vphi * math.cos(phi)

                norm = math.sqrt(vx*vx + vy*vy + vz*vz)
                if norm > maxnorm:
                    maxnorm = norm
            momentum.SetTuple3(i, vx, vy, vz)

        for i in range(0, mydata.GetNumberOfPoints()):
            [vx, vy, vz] = momentum.GetTuple3(i)
            vx = vx/maxnorm
            vy = vy/maxnorm
            vz = vz/maxnorm
            momentum.SetTuple3(i, vx, vy, vz)

    ###################################
    ##
    ## End:  Physics Analysis
    ##
    ###################################

def initialize(*args, **keywords):
    reg=core.modules.module_registry.registry
    reg.add_module(SwitchCoord)
    reg.add_input_port(SwitchCoord, "scalar_range", 
                       [core.modules.basic_modules.Float, 
                        core.modules.basic_modules.Float]) 
    reg.add_input_port(SwitchCoord, "min_density", core.modules.basic_modules.Float)
    reg.add_input_port(SwitchCoord, "omega", core.modules.basic_modules.Float)
    reg.add_input_port(SwitchCoord, "dataset", 
                       (reg.get_descriptor_by_name(
                'edu.utah.sci.vistrails.vtk', 'vtkStructuredGrid').module) )
    reg.add_output_port(SwitchCoord, "changed_dataset", 
                        (reg.get_descriptor_by_name(
                'edu.utah.sci.vistrails.vtk', 'vtkStructuredGrid').module) )

def package_dependencies():
    import core.packagemanager
    manager = core.packagemanager.get_package_manager()
    if manager.has_package('edu.utah.sci.vistrails.vtk'):
        return ['edu.utah.sci.vistrails.vtk']
    else:
        return []
</pre>