TIN / DTM Commands

Overview

The SDBox TIN/DTM toolset helps you build, inspect, and edit a triangulated surface directly inside your CAD drawing.

A typical workflow is:

• Select participating points with ZDTS.
• Create triangulation with ZDTMA (or inside a boundary with ZDTM) and rebuild using breaklines with ZDTMB.
• Inspect and refine with shading (TTH / TTHR), centers (TTG / TTGR), and editing tools (TTR, TTD, ZTIN).
• Export triangles when needed with ZXTIN.

Add New Points TTS

Adds extra (missing) survey points to an existing TIN workflow, without changing your original point numbering philosophy.

Use this command when you have already created a TIN/DTM and you need additional points that should participate in the triangulation.

Calculate Z details

Example for blue points measured and red points needed

Select Points for DTM ZDTS

Selects the surveyed points that will participate in the DTM (TIN) triangulation.

This is the point set definition step: you decide which point blocks/points are considered by the TIN commands.

Selection

Select points from the drawing. For advanced selection options (filters, block attributes, etc.), see: Object selection with filters.

Selecting DTM points in the drawing

Selection options / filters

Draw Standard Triangles ZDT1

Sets the triangulation mode to draw standard triangles.

When enabled, newly created triangles are drawn as normal triangulation elements (as opposed to exclusion triangles).

Draw Exclusion Triangles ZDT2

Sets the triangulation mode to create exclusion triangles (holes / forbidden areas).

Use this mode to mark triangles that must not produce contours or surfaces (e.g., buildings, water bodies, voids).

Exclusion triangle definition

Result after applying exclusion triangles

Open Boundary Triangles ZDTMA

Creates open-boundary triangles, typically used for edges where the surface must remain open.

This command is used when the triangulation should not be closed around the outside boundary (for example, when you want the surface to fade out naturally or when the boundary is incomplete).

Open-boundary triangulation example

No max side set for road example

Correct max side set for road example

Resulting open boundary triangles

Single Triangle Construction ZTIN

Creates or edits single triangles manually.

Use this command for local corrections when you need to force a specific triangle shape, typically after you detect an undesired triangulation due to sparse points or special terrain conditions.

Rebuild Using Breaklines ZDTMB

Rebuilds the triangulation based on breaklines.

Breaklines are linear constraints (e.g., curbs, ridges, edges of pavement) that force the TIN to respect sharp terrain features.

Rebuild triangulation using breaklines

Selection options / filters

Result after rebuild

Closed Area Triangulation ZDTM

Creates triangulation inside a closed boundary (polyline).

Use this command when you want the DTM to be strictly limited inside a specific area (e.g., a project boundary).

Boundary selection for closed-area triangulation

Command options (example)

Triangulation result inside boundary

Find Missing Triangles TTNO

Highlights triangles that should exist but are not currently drawn.

This command is useful during validation: you can step through the drawing and reveal missing triangles, then correct the triangulation using ZTIN or a rebuild command.

Example of missing triangles detection

Show Triangle Centers TTG

Calculates and displays the centers of the currently drawn triangles.

Triangle centers are a quick way to validate that the triangulation is complete and consistent.

Refresh Triangle Centers TTGR

Refreshes the triangle centers after edits.

Run this after operations such as deleting, swapping, or rebuilding triangles to ensure the displayed centers match the current state.

Shade Triangles TTH

Applies shading to triangles for easier visual inspection of the surface.

Shading is especially helpful to detect spikes, wrong connections, and local inconsistencies.

Shaded triangles for visual inspection

Remove Triangle Shading TTHR

Removes triangle shading.

Use this to return to a clean wireframe view after inspection.

Send Triangles to Back TTB

Sends the triangle entities behind other drawing objects (Draw Order: Back).

Useful when triangles obstruct other design entities during editing.

Triangles displayed behind other entities

Bring Triangles to Front TTF

Brings triangles in front of other drawing objects (Draw Order: Front).

Use this when you want triangle edges to be clearly visible during inspection.

Triangles displayed in front of other entities

Swap Two Triangles TTR

Swaps two triangles by selecting them, allowing fast local corrections.

This is a practical editing tool when you need to quickly improve temporary contours or the surface appearance without a full rebuild.

Delete Triangle TTD

Deletes a selected triangle.

Use this for local cleanup when a triangle connection is clearly wrong and should be removed before rebuilding or manually re-triangulating.

Toggle Triangle Layers TTV

Toggles the visibility of triangle layers.

If triangle layers are visible they will be turned off; if they are off, they will be turned on.

Toggle Point Layers SSV

Toggles the visibility of point layers used for DTM work.

Use this together with TTV to quickly switch between points-only, triangles-only, or combined views.

Bulk Delete Triangles ZEEDTM

Deletes triangles in bulk.

Use this when you want to clear a triangulation set (partly or fully) before rebuilding.

Selection options / filters

Delete Triangles Inside Polylines ZDTMD

Deletes triangles located inside selected polylines.

This command is commonly used to remove triangles inside areas where no triangulation should exist (e.g., buildings, retaining walls, asphalt, steps).

Export Triangles to File ZXTIN

Exports selected triangles to an external file format.

This export can be used by third-party applications for cross-sections and volume computations, or for interoperability workflows.

Drawing example

DTM Ribbon