Stereonet User Guide

The stereonet is where VRGS plots orientation data: the planes and lineations you have interpreted, and the dip and azimuth attributes of a mesh, as a pole per vertex or per triangle. It contours pole density, draws a rose diagram and a dip plot beside it, colours the net by a stress attribute, draws the kinematic analysis of a slope face, and exports everything as SVG or a spreadsheet.

Where to find it

Where	What you get
Charts panel	A stereonet that is always available beside the 3D view, tracking whatever is displayed.
Stereonet window (Home → Windows → Stereonet Window)	A full document window — the document view, which has everything: the mesh-pole layer, the key, the stress-attribute field and the kinematic analysis.

The two share their settings, so a change made in one is a change in the other. Some controls appear only in the stereonet window because the Charts panel does not draw what they control; those are called out below.

Almost all the controls are in the property sheet

The Stereonet ribbon tab now carries only zooming and pole selection. Everything about what is drawn lives in the property sheet (the Properties panel, shown whenever a stereonet has focus) and on the right-click menu. Both are documented below.

The right-click menu

Right-clicking anywhere on the net — in the 2D view or on the 3D stereosphere — opens one menu, grouped into four blocks. Toggles show a tick when they are on.

Display

Command	Effect
Show Stereonet	Draw the net itself (the grid and its frame).
Show Poles	Plot orientations as poles.
Show Planes	Plot orientations as great circles.
Show Contours	Density-contour the poles.
Show Rose	Draw the rose diagram.
Strike Values	Plot the rose as strike rather than dip azimuth. Available only while the rose is shown.

Selection

Command	Effect
Set Selected As → Bedding / Fractures / Cleavage	Re-type the selected orientations. The change goes back to the objects themselves, so it is reflected everywhere in the project.
View in 3D window	Fly the 3D view to the selected poles' centroid — or, with nothing selected, to the single pole under the cursor. The 3D window is brought to the front. Greyed when neither applies.
Group Selected	Move the selected orientations into a new Stereonet Group in the interpretation tree.
Invert Selection	Select what was not selected, and vice versa.
De-select all	Clear the selection.

From the net back to the outcrop

View in 3D window is the point of selecting on the stereonet: lasso a cluster of poles, and go and look at the part of the outcrop they came from.

View

Command	Effect
2D View	The flat stereonet on its own.
3D View	The stereosphere — the same data on a sphere you can rotate.
Split View (2D & 3D)	Both, side by side.

The stereosphere shares this menu, so you can switch back from inside it.

Export

Command	Effect
Spreadsheet	The plotted orientations as a table.
SVG Document → Stereonet Diagram	The net as a vector drawing, at publication quality.
SVG Document → Rose Diagram	The rose as a vector drawing.

The same picture goes into a report

Analysis reports insert stereonet and rose figures through these same writers, so a figure in a report and the SVG you export here are the same drawing.

Selecting poles

On the Stereonet ribbon tab:

Tool	What it does
Rectangle	Drag a rectangle; every pole inside is selected.
Ellipse	The same with an ellipse.
Polygon	Draw a closed polygon around a cluster.
Sector	Select an angular sector of the net.
Hide Unselected	Hide everything that is not selected, in the 3D view as well.

Selection is shared with the rest of VRGS — what you pick on the net is picked in the model and in the trees.

The tab's Navigation panel has Zoom To Fit, Zoom In and Zoom Out.

Plotting a mesh's dip and azimuth

Stereonet window only. A mesh is plotted from two of its attributes: one read as the dip of each vertex or triangle, the other as its azimuth (dip direction). Pick them under Contour Properties as Dip Attribute and Azimuth Attribute. They default to Dip and Azimuth, which is what VRGS calls the layers when it computes them, by either of two routes:

Run on the mesh	Writes	Plots
Attributes & Analysis → Geometry → Tensor Analysis, with Dip and Azimuth ticked (on a point cloud, Attributes & Analysis → Tensor Analysis)	Vertex attributes	A pole per vertex — the orientation of the surface around it, over the neighbourhood you set.
Attributes & Analysis → Geometry → Dip Angle, then Azimuth	Triangle attributes	A pole per triangle — each face's own orientation, with nothing to set.

The two routes write layers of the same names, and each replaces the other's. Running Dip Angle alone on a mesh that has been through Tensor Analysis leaves a triangle Dip beside a vertex Azimuth — a pair that cannot plot.

Any other pair of scalar attributes can be picked instead — ones imported from other software, say — provided they pass the checks below. The pickers, and Mesh Attributes in both Data Source lists, appear once a mesh in the view has two or more scalar attributes to choose from.

One such pair is Patch Dip and Patch Azimuth, the triangle attributes that Grow Planar Patches and Auto Structural Mapping write: every triangle of a patch plots with the plane fitted to the whole patch, so the net shows the extracted surfaces weighted by their number of triangles. Triangles in no patch have no value in either, so only the patches are plotted. See Patches on the Stereonet.

Another is Fabric Dip and Fabric Azimuth, which the Dimensionality Report writes and opens a Stereonet window on: each triangle's own orientation, folded so the dip never exceeds 90. The plain Dip layer from Dip Angle can, on a triangle whose normal points downward, and then fails the checks; the Fabric pair always plots.

One pair of picks serves everything in the window that plots a mesh:

• the density contours, when Data Source is Mesh Attributes;
• the rose and the dip plot, when the rose's Data Source is Mesh Attributes — azimuths into the rose, dips into the dip plot;
• the mesh Poles, under Mesh Properties;
• pole selection, which selects the matching vertices in the model — or the matching triangles, for triangle attributes.

The picks belong to the window, and like the Data Source settings they are not saved with the project: a new Stereonet window starts from Dip and Azimuth again.

Checking the picks

Before anything is plotted, the picks are checked on every mesh in the view that carries either of them. To plot, a mesh needs:

• both attributes, and two different ones;
• both scalar — one number per vertex or triangle, not a vector or tensor;
• both vertex attributes, or both triangle attributes;
• the same number of values in each. If they differ, one was computed on an earlier version of the mesh: compute it again;
• every Dip value within 0–90° and every Azimuth within 0–360°, give or take 0.01°;
• at least one vertex or triangle with both values set.

Null and NaN values count as no value: that vertex or triangle is skipped rather than held against the ranges. A mesh that fails any check is left off the stereonet — no contours, rose, poles or selection from it — while meshes that pass still plot. A mesh carrying neither attribute is simply not part of the plot.

The Attribute Status row under the pickers gives the verdict:

Status	Meaning
OK (n vertices / triangles)	Every mesh that carries the picks passes. n counts the vertices or triangles with both values set.
Partly valid: (in red)	Some meshes pass and plot; the rest are left off.
Invalid: (in red)	Nothing can plot.

A red status names the first problem. Select the row for the full explanation — every problem, with the mesh and attributes it concerns — in the description area at the foot of the Properties panel.

Until a bad pick is put to use, that row is the only place it is reported. Setting either Data Source to Mesh Attributes, switching the mesh Poles on, or changing a pick while any of those is in use, brings up a warning box explaining the problem, and writes a [WARNING] line to the Messages panel.

The checks cannot tell a strike from a dip direction

Both lie within 0–360°, so an attribute holding strike passes every check and plots 90° out. The Azimuth Attribute must hold the dip direction.

The property sheet

Select the stereonet and the Properties panel fills with three top-level groups. Groups remember whether you collapsed them.

Stereonet Display Properties

The group opens with a read-only census: a Source / N header, the number of Interpretations plotted, and a row per mesh plotted from its dip and azimuth, with its pole count. Each interpretation orientation is drawn as both a pole and a plane, so one N covers both.

Property	Description
Show Key	(Stereonet window only) A legend in the top-right margin: projection, N per interpretation type and mesh, the mesh-attribute colourbar, and the contour settings and their source.

Interpretation Properties

Property	Description
Colour by	Object = the per-type colours; Stratigraphy / Set = the project pick-list colours; Group = the data-tree group each object sits in (loose objects plot grey as Ungrouped). DFN poles keep their own per-set colours. Applies to poles and planes alike.
Poles	Plot the interpretation orientations as poles.
Pole Size	Pole radius, 1 (smallest) to 20 (largest).
Pole Border	A white ring behind each pole, so dark poles stay visible over contours.
Planes	Plot the interpretation orientations as great circles.

Mesh Properties

Stereonet window only, and greyed until at least one mesh has a Dip and Azimuth pick that passes its checks. Without one there is nothing to plot.

Property	Description
Colour by attribute	Colour the mesh poles by one of the mesh's attributes — mapped over that attribute's full data range — or by a single flat object colour. The options are the attributes on the same elements as the poles: vertex attributes when the poles come from vertex Dip/Azimuth, triangle attributes when they come from triangle Dip/Azimuth.
Colour Map	The colour map used for that attribute, and for the key's colourbar. Sequential maps only.
Poles	Plot the picked Dip/Azimuth as poles — one per vertex for vertex attributes, one per triangle for triangle attributes. Lasso-select these to select the matching vertices or triangles in the model.
Size	Mesh pole radius, 1–20.
Border	A white ring behind each mesh pole.
Use Attribute Filters	Honour the mesh's attribute filters on the stereonet (poles, contours and rose). Off by default, which plots every vertex or triangle with both a Dip and an Azimuth value, regardless of the filters set on the mesh.

The data-tree selection does not colour these

Mesh pole colours come entirely from this combo. The active layer in the data tree and the mesh's attribute filters have no bearing on them — that is what Use Attribute Filters exists to change.

Contour Properties

Show Contours is the master switch: everything below it is greyed until it is on — except Data Source and the mesh attribute rows under it, because the Dip and Azimuth picks also drive the mesh poles and the rose.

Property	Description
Show Contours	Draw spherical density contours.
Data Source	(Stereonet window only) Interpretations — orientation and scanline data; Mesh Attributes — the mesh attributes picked as Dip Attribute and Azimuth Attribute, below. Mesh Attributes and the three rows below appear once a mesh in the view has two or more scalar attributes. The rose has its own Data Source, and the pole layers are controlled separately.
Dip Attribute	(Stereonet window only) The mesh attribute read as dip, 0–90°: any scalar attribute on the meshes in the view, Dip by default. A vertex attribute gives a pole per vertex, a triangle attribute a pole per triangle. The contours, rose, mesh poles and selection all share this pick — see Plotting a mesh's dip and azimuth.
Azimuth Attribute	(Stereonet window only) The mesh attribute read as azimuth (dip direction), 0–360°, Azimuth by default. Must be the same kind as the Dip: both vertex or both triangle attributes.
Attribute Status	(Stereonet window only) Read-only: OK and how many vertices or triangles have both values — or, in red, Invalid: or Partly valid: and the first problem. Select the row for the full explanation, and see Checking the picks.
Method	Modified Kamb — an adaptive counting circle sized to the sample, contoured in σ (standard deviations above a uniform distribution), which highlights statistically significant maxima. Schmidt (1%) — a fixed 1%-area counting circle contoured in % of the data: the classic equal-area method, comparable between datasets.
Weighting	In-circle weighting. Exponential is the smooth Vollmer (1995) Kamb kernel; Inverse Area and Inverse Area Squared taper the count toward the edge of the counting circle. Exponential has no effect under Schmidt, which is a plain count.
Significance (σ)	1–5. Sets the counting area for Modified Kamb: lower gives tighter, more detailed contours, higher gives broader, smoother ones. Not used by Schmidt.
Contour Mode	Interval — draw a contour every N units. Levels — draw exactly N equally-spaced contours between zero and the data maximum.
Interval	The contour interval (1, 2, 3, 5, 10), in σ or %, depending on the method. Interval mode only.
Levels	The number of contours (5, 8, 10, 15, 20). Levels mode only.
Solid Fill	Fill the bands with colour-map colours.
Lines	Trace each contour with a black line — shown on their own when Solid Fill is off.
Line Width	1 (thinnest) to 20 (thickest).
Colour Map	The map used for the bands.
Reverse Colours	Flip the colour map.
Transparency	0 (opaque) to 100 (fully transparent), so poles stay readable over a filled net.

Which method to use

Use Modified Kamb to ask "is this cluster real?" — its σ contours answer that directly. Use Schmidt (1%) when the plot has to be compared against published nets, or against another dataset of a different size.

Grid Properties

Property	Description
Equal Area	Equal-area (Schmidt) projection. Uncheck for equal-angle (Wulff). Equal area is the default and is what density contouring assumes.
Major Lines	The 10° grid.
Minor Lines	The 2° grid.
Net Colour	Colour of the net lines, with Other… for a custom colour and Default to reset.
Cardinal Labels	N, E, S, W around the perimeter.
Degree Labels	Degree labels around the perimeter.
Degree Interval	Spacing between those labels: 10, 15 or 30°.

Rose Display Properties

Property	Description
Show Key	A rose legend in the top-right: data source, N, bin size, strike or dip azimuth, and the peak-count scale.
Frequency Labels	Label every other count ring with its value, up the north axis.
Data Source	(Stereonet window only) Interpretations or Mesh Attributes — the rose's own, independent of the contours'. Mesh Attributes reads the Dip and Azimuth picked under Contour Properties: azimuths into the rose, dips into the dip plot.
Bins	Bin width in degrees: 10, 15 or 30.
Petal Colours	Azimuth — coloured through a cyclic colour map. Group — the data-tree group colours.
Colour Map	The cyclic map used for azimuth petal colours.
Cardinal Labels	N, E, S, W around the rose.
Degree Labels	Degree labels at the bin boundaries.
Equal Area	Scale petal radius so petal area is proportional to frequency. Off gives linear scaling, which exaggerates the long petals.
Strike Values	Treat azimuths as axial strike lines: each measurement plots both ±90° from its dip azimuth, doubling the petals, and the key reports strike.
Shape	Full, North Half or South Half. The half rose is available when Strike Values is on — strike petals repeat at 180°, so half the circle already shows all of the data.
Density Ring	A 1° azimuth density ring around the rose.
Azimuth Dots	Every individual azimuth as a dot outside the rose.
Mean Arrow	The circular-mean azimuth, drawn solid over the petals.
Median Arrow	The circular-median azimuth, drawn dashed.
Arrow Width	Mean / median arrow line width, 1–10.

Equal area matters more than it looks

With linear scaling a petal twice as long looks four times as important, because the eye reads area. Equal Area is the honest default for a rose that is going into a figure.

Dip Plot Properties

The dip plot is a quarter plot of dip angle, drawn in the lower-right of the stereonet.

Property	Description
Show Dip Plot	Draw it.
Colour by	Dip — bins coloured by dip angle through the colour map. Group — bins stack per data-tree group in the group colours (loose objects stack grey as Ungrouped), and the dip key lists each group with its N.
Dip Bin	Bin size in degrees: 10, 15 or 30.
Degree Labels	Label every bin boundary, rather than just 0 and 90.
Equal Area	Scale bin length so bin area is proportional to count.
Mean Line	The mean dip, as a solid radial line.
Median Line	The median dip, dashed. Both use the rose's Arrow Width.
Colour Map	The map used for the bins, in Dip colour mode only.

Analysis Display Properties

Stereonet window only. Colours the whole net with a stress attribute computed from the project's stress state, evaluated over every plane orientation — so you can read off which orientations are prone to slip or to open — and draws the kinematic analysis of a slope face.

Property	Description
Stress Attributes	Draw the field. Mutually exclusive with the density Solid Fill (the control greys out while that is on); poles draw on top of it.
Attribute	Which attribute to plot — see the table below.
Colour Map	The map for the field. Sequential maps only; cyclic maps do not suit a 0–1 scale.

Attribute	Meaning
Slip Tendency (Ts)	τ / σn — propensity to reactivate in shear (0–1).
Dilation Tendency (Td)	(σ1 − σn) / (σ1 − σ3) — propensity to open (0–1).
Reduced-Risk Dilation (Tdn)	Td × (1 − Ts/Tsmax) — opening-favoured with low shear risk (0–1).
Fracture Susceptibility (Sf)	(σn − Pf) − (τ − C0)/μ — the pore-pressure rise needed to reach failure, in MPa.
Opening Angle (OA)	atan(τ / (Pf − σn)) — Jolly & Sanderson (1997), in degrees.

Sf and OA need real stress magnitudes

Ts, Td and Tdn are ratios and work from the stress shape. Fracture Susceptibility and Opening Angle are in MPa and degrees and are only meaningful if the project's stress magnitudes are real values, not placeholders.

Kinematic Analysis

The kinematic analysis of one slope face: the construction for a failure mode, its critical zones shaded over the net, and a key listing the percentage of each set's planes — or of the lines where two sets' planes meet — that are critical. Each folder of plane interpretations is one discontinuity set, even when two folders share a name; lineations are left out, and so are the originals Auto-cluster copied into its clusters. The same tests map a whole mesh or point cloud; see Slope Stability.

Property	Description
Kinematic Analysis	Draw the analysis.
Failure Mode	Planar Sliding, Wedge Sliding, Flexural Toppling or Direct Toppling.
Slope Dip	Dip of the slope face, 0–180°; above 90 it overhangs.
Slope Dip Direction	The direction the face looks.
Friction Angle	Friction angle of the discontinuities; it starts from the project's friction coefficient.
Lateral Limit	How far a plane or line may swing from the slope's direction and still count: 20° for planar sliding and direct toppling, 30° for flexural toppling. Wedge sliding has none.

The zones sit over the density contours and under the poles and planes, the curves over the planes, and the kinematic key below the stereonet key. With Remove Regional Dip on the zones are not drawn. SVG export includes all three.

Tips and troubleshooting

• The net is empty. Nothing displayable is plotted: check the interpretations are visible, and that Show Poles or Show Planes is on.
• Mesh Properties is greyed out. No mesh has a Dip and Azimuth pick that passes its checks. Read the Attribute Status row under Contour Properties — select it for the full explanation — then correct the picks, or give the mesh the attributes it lacks: Tensor Analysis for a pole per vertex, or Geometry → Dip Angle and Azimuth for a pole per triangle.
• Mesh Attributes is not in the Data Source list. It appears once a mesh in the view has two or more scalar attributes to pick a Dip and an Azimuth from.
• A warning says the Dip and Azimuth cannot be plotted. A pick has failed a check on at least one mesh. The warning names the mesh and the problem, and that mesh stays off the stereonet until the picks are put right. Values in another convention — a signed azimuth of −180 to 180°, say — fail the range check.
• Mesh poles are missing where I filtered the mesh. That is the default: the stereonet ignores attribute filters. Tick Use Attribute Filters to honour them.
• The Stress Attributes checkbox is greyed. Density Solid Fill is on; the two fields cannot both colour the net.
• Contours look different from a published plot. Check the Method — Kamb σ contours and Schmidt % contours are not the same quantity — and that Equal Area is on.
• The rose has twice as many petals as I expect. Strike Values is on, which plots each measurement axially at ±90°.
• A control I remember from the ribbon has gone. The Display, Contours and Rose panels moved off the ribbon into the property sheet and the right-click menu.

See also

• Analysis Reports — putting a stereonet or rose figure into a document.
• Grow Planar Patches and Auto Structural Mapping — generating the orientations the net plots from the planar faces of a mesh, as one object per patch or as the Patch Dip and Patch Azimuth triangle attributes.
• Charts, Histograms and Filtering — the same stereonet in the docked Charts panel, alongside the attribute charts.
• Fracture Intensity Mapping — the intensity attributes derived from the same data.
• Slope Stability and its method — the kinematic analysis on the net, and mapped over a mesh or point cloud.