Editing a Numeric Interpolant

To edit a numeric interpolant, you can either double-click on the interpolant in the Interpolants folder or right-click and select Open. When creating an interpolant, only a basic set of parameters is used. The Edit Interpolant window provides finer controls over these basic parameters so you can refine the interpolant to factor in real-world observations and account for limitations in the data.

For a multi-domained interpolant, these parameters can be changed for the parent interpolant, and the trend, clipping, transformation and interpolation settings can be changed for the sub-interpolants.

Adjusting the Values Used

The Values tab in the Edit Interpolant window shows the values used in creating the interpolant and provides options for filtering the data. Although you cannot change the values used to create an interpolant, you can filter the values using the Query filter and Surface filter options.

You can adjust the values using a contour polyline or by adding points. Both options are available by expanding the interpolant in the project tree, then right-clicking on the values object:

These options are described below in Adding a Contour Polyline and Adding Points.

To apply a query filter, tick the Query filter box in the Values tab and select the available queries from the list.

To change the object used as the Surface filter, select the required object from the list. Note that the list contains an object that defines the interpolant’s own boundary, which can be adjusted in the Boundary tab.

Adding a Contour Polyline

Adding a contour polyline is a useful tool for manually adjusting a surface to make it more geologically reasonable. To start adding a contour polyline, draw a slice where you wish to adjust the surface and decide what value you will assign to the contour line. Next, right-click on the values object and select New Contour Polyline. The next step is to choose whether you will draw a new polyline or use one already in the project:

Only GIS lines, polylines imported into Leapfrog Geo or polylines created using the straight line drawing tool can be used to create contour lines.

Enter the value to be used for the contour and a name for it. Click OK. If you have chosen the New Drawing option, the new object will be created in the project tree and drawing tools will appear in the scene. Start drawing in the scene as described in Drawing in 3D. When you have finished drawing, click the Save button (). The new contour will automatically be added to the model and will appear in the project tree as part of the interpolant’s values object.

To change the value assigned to a contour polyline, double-click on the interpolant in the project tree. In the Values tab, contour polylines and their assigned values are shown in the User contour values table:

To change the value on a contour, click in the Value column and edit the entry.

To edit the polyline, right-click on it in the project tree and select Edit Polyline or add it to the scene and click the Edit button () in the shape list. If you wish to remove a contour polyline from the interpolant, right-click on it in the project tree and select Delete or Remove.

Adding Points

To add points to a numeric interpolant, right-click on the values object in the project tree and select Add Values. Leapfrog Geo will display a list of all suitable points objects in the project. Select an object and click OK.

A hyperlink to the points object will be added to the values object in the project tree. To remove the points object, right-click on the points object and select Remove.

Compositing Parameters for a Numeric Interpolant

When a numeric interpolant has been created from uncomposited values, compositing parameters can be changed by double-clicking on the interpolant in the project tree, then clicking on the Compositing tab.

The Compositing tab will only appear for interpolants created from uncomposited drillhole data.

You can composite in the entire drillhole or only where the data falls inside the interpolant boundary. See Numeric Composites for more information on the effects of the Compositing Length and Minimum Coverage settings.

Adjusting the Interpolant Boundary

To change a numeric interpolant’s boundary, double-click on the interpolant in the project tree, then click on the Boundary tab:

Controls to adjust the boundary will also appear in the scene.

Tick the Use Topography box to use the topography as a boundary. The topography is normally not used as a boundary for interpolants and so this option is disabled when an interpolant is first created.

The Boundaries list shows objects that have been used to modify the boundary. You can disable any of these lateral extents by unticking the box.

Lateral extents can be used to restrict modelling to a particular area of interest; for example, modelling can be restricted to a known distance from drillholes by applying a distance function as a lateral extent.

Extents do not need to be strictly vertical surfaces. For example, an interpolant could use a geological model volume as a lateral extent, which is the case here, where interpolation has been restricted to a volume of interest from a geological model:

In the project tree, we can see that the QzP volume from a geological model has been used as a lateral extent:

Techniques for creating lateral extents for interpolants are similar to those for creating lateral extents for geological models. See Modifying the Model’s Boundary for more information.

Clipping and Transforming Values for a Numeric Interpolant

To clip data and apply a transformation to a numeric interpolant, double-click on the interpolant in the project tree, then click on the Value Transform tab:

The options for Transform Type are None and Log. Log uses a natural logarithm to compress the data values to a smaller range. This may be useful if the data range spans orders of magnitude. The function used is:

ln(x+s)+c

where s is the Pre-log shift and c is a constant. In order to avoid issues with taking the logarithm of zero or a negative number, Pre-log shift is a constant added to make the minimum value positive. The value of the pre-log shift will automatically be chosen to add to the minimum value in the data set to raise it to 0.001. This constant is then added to all the data samples. You can modify the value of the Pre-log shift, as increasing this value further away from zero can be used to reduce the effect of the natural logarithm transformation on the resultant isosurfaces.

Note that a further constant, c, is added to the natural logarithm of the data with the pre-log shift added to it. If there are any negative numbers that result from taking the natural log of the data, the absolute value of the most negative number is taken and added to all the transformed data results. This will raise the value of all the data so the minimum data value is zero. The value of c is chosen automatically and cannot be modified.

Bin count defines the number of bins, where a larger bin count results in a finer histogram.

If you tick the Do pre-transform clipping option, you can set the Lower bound and the Upper bound to cut off values that are too low or too high. For example, if you set the Upper bound from 14.00 to 10.00, grade values above 10.00 will be regarded as 10.00.

Changing the Trend for a Numeric Interpolant

You can apply a global trend or a structural trend to an interpolant. To do this, add the interpolant to the scene, then double-click on the interpolant in the project tree. Click on the Trend tab in the Edit Interpolant window.

See:

Using a Global Trend

The easiest way to change the trend applied to an interpolant is using a global trend set from the moving plane.

Click View Plane to add the moving plane to the scene, then click on the plane to view its controls. You may need to hide part of the interpolant to click on the moving plane:

You can also use the Set to list to choose different options Leapfrog Geo has generated based on the data used to build the model. Isotropic is the default option used when the model is created.

The Ellipsoid Ratios determine the relative shape and strength of the ellipsoids in the scene, where:

  • The Maximum value is the relative strength in the direction of the green line on the moving plane.
  • The Intermed. value is the relative strength in the direction perpendicular to the green line on the moving plane.
  • The Minimum value is the relative strength in the direction orthogonal to the plane.

Click OK to regenerate the model and view changes.

Using a Structural Trend

You can also set the trend for an interpolant from a structural trend. First, you must create or import the required mesh and create a structural trend. See Structural Trends for more information.

Once the structural trend has been created, add it to the interpolant by double-clicking on the interpolant in the project tree, then clicking on the Trend tab. Select the Structural Trend option, then select the required trend from the list:

Click OK. The trend will be added to the model and will appear as part of the model, as shown:

When you apply a structural trend, you cannot use the Linear interpolant. See Interpolant Functions for more information.

Once a structural trend has been defined for the model, you can edit it by clicking on the trend hyperlink in the project tree, then opening the structural trend applied to the interpolant. The Structural Trend window will appear. See Structural Trends for information on the settings in this screen.

The structural trend information included as part of the interpolant is a link to the original structural trend. When you change the structural trend that is part of the interpolant, the changes are also made for the original structural trend.

When a structural trend that is Strongest along meshes or Blending is used, the model will regress to the global mean trend away from the meshes. The global trend that will be used is set in the Global Trend tab for the structural trend.

Adjusting Interpolation Parameters

To adjust interpolation parameters for a numeric interpolant, double-click on the interpolant in the project tree, then click on the Interpolant tab:

Two models are available, the spheroidal interpolant and the linear interpolant. See The Spheroidal Interpolant Function and The Linear Interpolant Function for more information on the settings in this tab.

Output Settings for a Numeric Interpolant

You can change the parameters used to generate interpolant outputs by double-clicking on the interpolant, then clicking on the Outputs tab.

The Evaluation limits apply when interpolants are evaluated against other objects in the project. When the limits are enabled, all values outside the limits will be set to the Minimum and Maximum.

When Exact clipping is enabled, the interpolant isosurface will be generated without “tags” that overhang the interpolant boundary. This setting is enabled by default when you create an interpolant.

To add a new isosurface, click the Add button and enter the required value. To delete an isosurface, click on it in the list, then click the Remove button. You can also change the colours used to display the isosurfaces by clicking on the colour chips.

If you find that grade shells are overlapping, the resolution may be too coarse. Set Default resolution to a lower value or enable adaptive resolution in the Outputs tab. See Surface Resolution in Leapfrog Geo.

Click OK to regenerate the interpolant and view changes.