Glossary

The words VRGS uses, in alphabetical order, each with a link to the page that explains it fully.

Active descriptor

The facies, contact and unit on the left of the Interpretations tab. Whatever you digitise next is given them. See Basic Interpretation.

Active object

The one object a context tab and its tools act on, such as the mesh a log follows or the geopolygon being edited. Set it with Make Active on the object's tree menu.

Contact

A picked boundary between rock bodies, such as a formation top, an unconformity or a bed boundary. Contacts are one project-wide list in Collections → Contacts, so the same contact can be traced on the outcrop, picked on logs and correlated between them. See Contacts, Units and Intervals.

DFN (discrete fracture network)

A stochastic model of fractures as discs or polygons, generated to match the sets and intensities measured on the outcrop. See the DFN user guide.

DEM (discrete element model)

A model of rock as bonded particles, used to grow fractures under load. Not a digital elevation model in VRGS. See the DEM user guide.

Facies

A named rock type with a colour and pattern, given to beds, geopolygons, points and mesh vertices. Facies are kept in Collections → Facies.

Geopolygon

An outline digitised on the outcrop, around a geobody for example, that can be extruded into a solid. See the Geopolygon guide.

Grade

The quality VRGS gives every plane it fits from your clicks: excellent, good or rejected, from the published tests of Tavani et al. (2024). See How good is the pick?

Interval

A named span of beds between a younger and an older contact, such as a formation, a member or a channel belt, followed from log to log. See Intervals.

LOD (level of detail)

Lower-resolution copies of a mesh or point cloud drawn when it is far from the camera, so large models stay responsive. See Level of Detail on meshes.

MT, TVT, TST

The three thicknesses of a log. MT, measured thickness, is the distance along the log path. TVT, true vertical thickness, is measured vertically. TST, true stratigraphic thickness, is measured perpendicular to bedding, and is the one to compare between sections, as long as the bedding dip is right. See Getting the thicknesses right.

Orthopanel

A flat image of the outcrop projected onto a plane you choose, for drawing on or printing at scale. See Orthopanels.

P10, P21, P32, P33

Fracture intensity measures. P10 is fractures per unit length of a scanline or borehole. P21 is trace length per unit area of outcrop, which you can measure directly. P32 is fracture area per unit volume, the scale-independent measure a DFN targets. P33 is fracture volume per unit volume. P21 and P32 are both in m⁻¹ but are not the same number. See Fracture Intensity Mapping.

Pivot

The point the 3D view rotates about. Target Zoom sets it to a point you click. See Navigating the 3D view.

Scenario

In interpretation version control, a named choice of one variant for each feature. Applying a scenario swaps the whole interpretation at once. See Interpretation Version Control.

Scene

A saved record of which objects are shown, which a flight path or field trip can switch to as it goes. See Flight Paths.

Set

A discontinuity set: a tag on measured planes saying which family they belong to, given by hand or by Auto-cluster. Sets are listed in Collections → Sets and drive set statistics, joint strength, kinematics and DFNs. See Geomechanics.

SfM (structure from motion)

Photogrammetry: building cameras, a point cloud and a mesh from overlapping photographs. See the SfM user guide.

SLPK

Scene Layer Package, the Esri I3S file for a tiled, multi-resolution 3D model. VRGS reads SLPK files and writes them from a textured mesh. See Exporting a tiled model (SLPK).

Unit

A stratigraphic unit: the rock between two contacts. Scan lines, orientations, geobodies and geopolygons can be given one. See Contacts, Units and Intervals. On a log, each bed is also called a log unit.

Variant

In interpretation version control, one admissible interpretation of a feature, kept beside the others. See Interpretation Version Control.

Vulkan, OpenGL

The two renderers behind the 3D view. Vulkan is the default; a few older tools work only in OpenGL. See Why Is This Greyed Out?