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Basic Filtering

In this tutorial we will look at some of the filters that are available and how these can be applied to the objects in the pipeline to process the data in some way.


Numerous filters are available for a variety of uses, and are subdivided into categories to make them easier to locate. The alphabetical group contains all filters, including those not listed in other subcategories. We will focus mainly on the Common filters, but will also include some of the others. The common filters are available via the Common Filters toolbar which can be turned on in the View menu.

  • From the demo folder, open the Lens..vtp and Drifts.vtp datasets, and from the sample dataset folder open the Microseismic.vtm dataset.
    • When all three datasets are applied to the pipeline, change the visibility so only the Lens dataset is visible in the render view.
    • Change the viewpoint to look along the positive X axis.

 The Clip Filter

  • Select the Lens dataset in the pipeline and apply a color.
    • With the dataset selected, click on the Clip filter icon on the Common Filters toolbar, or select the filter under Filters > Common > Clip.
    • A bounding box appears in the render view, including a red rectangle identifying where the clipping will take place.
    • Click on the Y Normal button to switch the direction of the plane.
    • Slightly rotate the view so you can see the clip plane, click on the red edge so the plane surface appears green, and drag the plane to change the clip area.
    • Click on Apply; the side with the arrow head remains, the other side is removed.
    • Click on the Inside Out checkbox and apply again; the other side of the plane is now visible.
    • Switch to the Display tab, choose a different color, and scroll down to the Transformation section.
    • In the Translate fields, enter -350, -100 and 0, and turn on the visibility of the original Lens dataset; we now see the original dataset in the background and the clipped section in front.
    • Click on the eye icon for the Clip filter to hide it in the render view.

 The Calculator

  • Select the Lens dataset in the pipeline, then click on the Calculator icon on the toolbar or select the filter under Filters > Common > Calculator.
    • From the Scalars drop-down, select coordsZ and change the Result Array Name to Elevation.
    • Click the Apply button.
    • The dataset is now colored along the Z coordinates, in this case creating an elevation view. If the coloring isn't automatically applied, click on the Display tab and select the Elevation array in the Color By drop-down.
    • You can use the calculator to perform all kinds of calculations on the various aspects of the dataset. Note that there actually is an Elevation filter in the Alphabetical filter list.

The Threshold Filter

  • With the calculator object selected in the pipeline, click on the Threshold icon or select the filter under Filters > Common > Threshold.
    • Change the Lower Threshold by moving the slider to approximately 1600, and apply the filter; the lower sections of the lens disappear.
    • Change the Upper Threshold by entering 1750 into the text field, and apply the filter; part of the top section of the lens disappears.
    • The Threshold filter will always show you the range available for the scalar chosen in the drop-down; in this case, Elevation was the only scalar available, so we didn't have to select it. The thresholds are easily changed using the sliders or by typing in the values.

The Slice Filter

  • With the threshold filter object selected in the pipeline, click on the Slice Filter icon or select it from the Filters menu.
    • Accept the default values and apply the filter; we now see an outline of the lens sections that exist on the slice plane.
    • Select the slice plane and drag it to change the origin of the plane, and apply the filter to see the lens outlines change.
    • Select one end of the arrow (the line passing through the data) and drag it to change the angle of the plane, then apply the filter.
    • Remove the checkmark in the Show Plane checkbox to see only the slice in the view.

The Contour Filter

  • Toggle the visibility so the slice is hidden and the Drifts dataset is visible in the render view.
    • Select the Drifts dataset in the pipeline and color it by the Smin array.
    • Click on the Contour icon on the toolbar or select it from the Filters list.
    • In the Contour By drop-down, select the Smin array, and press the Delete All button to remove all current values; the values in the list do not update when a different array is chosen, so it is always a good idea to delete all the current values when choosing a new array.
    • Press the New Value button, enter a value of 30, and apply the filter; only those sections where the Smin is 30 are visible in the view, and you can add as many specific values as required.
    • Delete all the values, press the New Range button, accept the defaults and click OK; by default 10 steps are chosen from the available range of values.
    • Apply the filter; the render view now shows those sections of the drifts dataset that meet the Smin values listed.
    • Delete all the values and press the New Range button again, but this time we will change the From section to -30000 and the To section to 1, still using 10 steps.
    • Apply the filter; notice that the view changes to show only those sections that meet these new Smin values.
    • Try out different combinations and change the number of steps.

The Glyph Filter

  • Toggle the visibility so the Contour filter image is hidden and the Drifts image is visible.
    • Select the Drifts dataset and apply the Glyph filter using the default settings; the resulting image shows arrows coming off the drifts sections, but doesn't really give us any information about the dataset, so even though the glyph filter was available, it doesn't necessarily provide meaningful results for all the datasets it can be used on .
    • Delete the Glyph filter and hide the Drifts dataset

  • Toggle the visibility for the Microseismic dataset and select it in the pipeline; colorful points appear in the render view.
    • Select the Glyph filter.
    • Select the Size option in the Scalars drop-down and change the Glyph Type to Sphere.
    • Make sure the Scale Mode is set to scalar, and apply the filter; several spheres appear in the render view.
    • If the Microseismic dataset is still visible, you will notice that many points exist without spheres; this is because the Glyph mode has a setting for the maximum number of point, which defaults to 5000.
    • Change the Maximum Number of Points to 50000 and apply the filter; additional spheres appear in the render view.
    • Hide the Microseismic dataset, so the spheres are more easily visible; the spheres appear in different sizes in the render view because we told the filter to scale the spheres based on the Size scalar array.
    • Look at the Color By option on the Display tab; we are coloring by Date, so spheres have the same color if the seismic activity occurred at approximately the same time.
    • Switch the Color By option to Size so all the spheres of the same size have the same colors.

The Proximity Threshold Filter

  • Toggle the visibility so only the original Lens and Drifts datasets are visible in the render view.
    • Select the Drifts dataset in the pipeline and then click on the Proximity Threshold filter under Filters > Mirarco or in the alphabetical list.
    • The Input Editor window allows you to select the Input and Source for filters that require two input datasets; the dataset that was selected in the pipeline is automatically entered into the Input field.
    • Click on the Source radio button and select the Lens dataset in the Select Source area; the Pipeline Preview shows what the resulting pipeline will look like when the filter is created.
    • Click on OK.
    • The Distance field defaults to -1; change it to 300, then apply the filter.
    • The render view shows only the Lens dataset; change the Color By option to Distance (if required), and toggle the visibility so the Drifts dataset is also visible.
    • Looking at the image, we can see that those sections of the lens that are closest to the Drifts are colored the same, and the coloring changes as the distance increases.

  • To change the input(s) of a filter, right-click on the filter object in the pipeline and select the Change Input option to display the Input Editor window.
    • Change the Input to the Lens dataset and the Source to the Drifts dataset using the radio buttons and the Select Source area, then click OK.
    • Now the view shows the Drifts dataset colored by distance depending on how close the drifts are to the lens.

The Cell to Point and Point to Cell Filters

  • Toggle the visibility so the Microseismic dataset is the only one visible in the render view.
    • Select the Microseismic dataset in the pipeline, switch to the Display tab and look in the Color By drop-down; this dataset contains only point data arrays.
    • Some filters only work on point data, whereas others only work on cell data; two filters exist to convert the dataset as required.
    • With the Microseismic dataset highlighted, look under Filters > Alphabetical; the Cell Data to Point Data filter is grayed out because we already have point data, but the Point Data to Cell Data filter is available.
    • Select the Point Data to Cell Data filter; the Properties tab shows an option to Pass Point Data; check off this area so the resulting object contains both the point and cell data, and apply the filter. For the Cell Data to Point Data filter, a Pass Cell Data checkbox performs the same function.
    • Select the filter in the pipeline and look at the Color By drop-down on the Display tab; cell and point arrays now exist for the data, and many additional filters are now available in the Filters menu.

We have now looked at several of the filters that are available in ParaViewGeo, and have learned how to apply them and how to change a filter's input if required. We've also seen that two filters exist than can be used to manipulate the data so many other filters become available.

Click on the Disconnect icon and choose Discard to clear the pipeline.

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