Surface Resolution in Leapfrog Geothermal

In Leapfrog Geothermal, meshes are used to represent surfaces in the form of vertices and triangles that define the 3D shape of the surface. The resolution of a surface is controlled by the size of the triangles used to create a surface. A lower surface resolution value means smaller triangles and, therefore, a finer resolution. A higher surface resolution value will take less time to process but the surface may not show the level of detail required.

When a surface is imported, Leapfrog Geothermal automatically sets a surface resolution based on the information in the file. It is not possible to change the resolution of surfaces imported into Leapfrog Geothermal. The exception is elevation grids (see Importing an Elevation Grid).

When surfaces are created, Leapfrog Geothermal sets a default resolution based on the data available. You can set a lower value, but calculations will take longer.

Adaptive Isosurfacing

The resolution for many surfaces can be adaptive; that is, areas closer to data will have a finer resolution than areas further away from data.

To see the effect of different resolution settings, consider a simple geological model of three rock types. Here, the surface resolution is set to 50 and the adaptive isosurfacer is disabled:

Here, the resolution has been reduced, which results in smaller triangles:

For both resolution settings above, the triangles are the same size everywhere in each surface, even where real data is available. Once the adaptive isosurfacer has been enabled, the triangles closer to the wells are smaller than those further away:

Areas of the surface that have large triangles indicate that there is less data in those areas to guide the interpolation of the surface.

Single Pass Isosurfacing

When a mesh is generated, a point in space needs to be defined for each vertex and there is a performance/accuracy trade-off for this. The typical process is iterative, with each pass refining the positioning decision more accurately. For large, complex meshes with a fine resolution and a complex interpolant, this can take some time. In practice, the average (RMS) distance between the vertex points selected for single- and double-pass meshes will be almost insignificant, less than 1% of the mesh resolution. In some cases the impact on speed of processing due to adding a second pass can be as much as 50% for large, complex meshes.

Leapfrog Geothermal uses single pass isosurfacing by default to take advantage of the performance improvements, recognising that the accuracy of the mesh is typically adequate with a single pass. To take advantage of the higher accuracy provided by a double-pass mesh generation, untick the Use single pass isosurfacing option. Because this option can be changed later, you can leave this option ticked initially and change it later. This can be especially useful as you iterate through a number of options when choosing your surface resolution settings, because initially you will be less concerned about the accuracy while focusing on the smoothness-processing time trade-off associated with choosing the resolution. Then you can try Use single pass isosurfacing unticked to compare the difference in processing time and consider the differences between the generated meshes and decide which setting you want to use for your project.

Here a scene has been rendered with both 1m (top) and 10m (bottom) surface resolution, with Use single pass isosurfacing ticked and unticked. The arrows are used to point out subtle differences due to this setting.

Controlling Surface Resolution in Leapfrog Geothermal

In Leapfrog Geothermal, the resolution for different types of surfaces can be controlled as follows:

 

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