TIN SURFACES
STREAM is TIN surface software as much as it is a DEM viewer: it triangulates your survey points, lines and areas into a triangulated irregular network, opens LandXML surfaces, and gives the TIN its own ribbon — shade it by elevation or slope, edit node elevations, add nodes, flip edges, delete triangles, clip to an area, translate it, check it for overlapping triangles and holes, compute cut and fill against the terrain, and write it out as DXF 3DFACE or a LandXML surface with its coordinate system. All of it on your own Windows machine, offline.
A TIN — triangulated irregular network — is a surface made of triangles whose corners are measured points. Unlike a DEM grid it keeps every surveyed point exactly where it was measured, follows breaklines as triangle edges, and stays light where the ground is flat. It is the form that civil and mining exchange formats such as LandXML and DXF 3DFACE carry, and the form a design surface takes before it is applied to the terrain.
In STREAM a TIN is a surface record in the layer tree. Select it and the ribbon switches to the TIN Model tab, where every tool acts on that one surface: viewing, editing, creation, checking and export. Nothing in the tab rewrites the DEM unless you ask it to.
TIN surfaces arrive three ways: by triangulating the vertices of selected points, lines and areas (Delaunay, with CTRL for several objects or a whole layer by name), by lofting a ruled surface between lines in the order you selected them, or by opening a LandXML file whose Surface definition becomes a triangle surface.
Triangulate builds a Delaunay TIN from the vertices of every selected point, line and area — CTRL adds objects, a layer name takes the whole layer. Ordered Triangulate makes a ruled surface between neighbouring lines in selection order, matching lines with different vertex counts by normalised station; its output is 3DFACE triangles.
Colour the model by elevation, by triangle slope, flat, or as a wireframe of edges only; choose a thin or thick edge; label nodes with their elevation or triangles with their number; show the nodes as points; hide the surface without removing it. The choice is saved with the record and comes back with the project.
Edit Surface opens a floating panel with two modes. Enter Elevation: click a node, type its Z, and every triangle sharing that corner moves with it. Add Node: click inside a triangle, it splits into three and the new node takes its elevation from the surface. X, Y and Z of the selected node can be typed directly; nothing is written until you Apply.
Flip Triangle turns the shared edge of two neighbours without changing any elevation — the fix for thin slivers and a ridge that runs the wrong way. Delete Triangle marks triangles for removal, a second click unmarks. Clip to Area deletes every triangle outside a selected area; a triangle the boundary crosses is split, and the cut vertex takes its elevation from the source triangle's plane.
Move the whole model by X, Y and Z at once — every triangle shifted, in your display units. Each edit — translate, clip, delete, repair — has its own undo on that model, and a second Undo redoes. A message names what was undone.
Create Outer Boundary writes the model's outline as a 3D area record, one per separate part, ready to be the scope of a volume; Generate Points writes the model's nodes as a point record with duplicates merged, elevations taken from the model, not sampled from the terrain.
Correct Terrain to Model rewrites the DEM under the surface to match the triangles — the same machinery as terrain editing. Volume to Model computes cut and fill between the surface and the terrain in the background without touching the DEM.
Model Check searches without changing anything and reports counts: triangle pairs overlapping in plan and the largest overlap ratio, exact duplicate triangles, plan folding and bow-tie winding; holes inside the mesh with their total area, torn (non-manifold) edges, unclosed boundary chains and the number of separate parts; degenerate zero-area triangles and non-finite vertices. Repair deletes the degenerate, duplicate and overlapping triangles — it never fills a hole — and is undoable.
Select the survey points, breaklines and boundary areas that should shape the surface — CTRL to add objects, or a whole layer by name.
Run Triangulate. A Delaunay TIN is built from every vertex and appears as a surface record; select it and the TIN Model tab opens.
Switch shading to Slope or Wireframe and label the nodes. Slivers, wrong ridges and stray points show at once.
Flip edges that cross a ridge, delete triangles that bridge a gap, add nodes where the surface needs a point, type the elevation of a node that is wrong. Apply when the counters say what you meant.
Clip to the survey boundary, then run Model Check. Repair removes overlaps and duplicates; a hole is reported, not filled — add points there and triangulate again.
Compute cut and fill against the terrain, correct the terrain to the model, or write the surface as DXF 3DFACE or a LandXML surface with its CRS and EPSG code.
| Finding | What it means | Repair |
|---|---|---|
| Overlapping triangle pairs | Two triangles cover the same ground in plan; the largest overlap ratio is given | Deleted |
| Duplicate triangles | The same three corners twice | Deleted |
| Plan folding / bow-tie winding | The surface folds over itself or a triangle's winding reverses | Reported |
| Holes inside the mesh | Enclosed gaps, with count and total area | Reported — never filled |
| Torn (non-manifold) edges | An edge shared by more than two triangles or by none where it should be | Reported |
| Unclosed boundary chains | An outer edge that does not return to its start | Reported |
| Separate parts | How many disconnected pieces the model has | Reported |
| Degenerate triangles | Zero-area triangles | Deleted |
| Non-finite vertices | A corner with an invalid coordinate | Reported |
A triangulated irregular network: a surface of triangles whose corners are measured points. It keeps every surveyed point where it was measured, carries breaklines as triangle edges, and is the form LandXML and DXF 3DFACE exchange. In STREAM it is a surface record with its own ribbon tab.
Select points, lines and areas — CTRL for several, or a whole layer by name — and run Triangulate; a Delaunay TIN is built from their vertices. Ordered Triangulate instead lofts a ruled surface between lines in the order you selected them. A LandXML file with a Surface definition also opens as a TIN.
Yes. Edit Surface, mode Enter Elevation: click the node and type its Z; every triangle that shares that corner moves with it. X, Y and Z can also be typed in the panel. Changes are counted and written only when you press Apply; Cancel leaves the model untouched.
Clip to Area deletes the triangles outside the selected area. A triangle the boundary crosses is split rather than dropped, and the vertex created on the cut takes its elevation from the plane of the source triangle — the surface keeps its shape right up to the edge.
Two neighbouring triangles share an edge that can run either diagonal of their quadrilateral. When Delaunay picks the diagonal that cuts across a ridge or a ditch, flipping it puts the edge along the feature without moving any point or changing any elevation.
Overlapping triangle pairs and the largest overlap ratio, exact duplicates, plan folding and bow-tie winding, holes inside the mesh with their total area, torn non-manifold edges, unclosed boundary chains, the number of separate parts, zero-area triangles and non-finite vertices. It changes nothing.
No. Repair deletes degenerate, duplicate and overlapping triangles and reports how many were removed. A hole stays a hole — add points there and triangulate again. Repair is undoable.
No. The surface is a separate record. The DEM changes only when you run Correct Terrain to Model, which rewrites the terrain under the surface to match the triangles.
Yes. Volume to Model computes cut and fill between the selected surface and the visible terrain in the background, without changing the DEM. Create Outer Boundary gives you the surface's outline as an area to use as the scope of other volume tools.
Write it as DXF 3DFACE — one face per triangle, the selected surface only — or as a LandXML surface, which carries the project name, coordinate system description and EPSG code so the receiving software opens it in place.
Neither replaces the other. A grid streams and computes fast over gigabytes; a TIN honours every measured point and every breakline. STREAM keeps both: the terrain is a DEM, design and survey surfaces are TINs, and the two are compared with Volume to Model or merged with Correct Terrain to Model.
Free beta for Windows x64. Works fully offline with GeoTIFF, LAS/LAZ and DXF.
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