Overview

This article details best practices for creating, organizing, and managing OpenX Designer terrain models. It covers terrain model components, existing complex terrain setups, clipping strategies, graphical filter workflows, and final combined surfaces designed to preserve dynamic rules while optimizing processing performance.

1. Terrain Model Components and Symbology

• Definition: A terrain model is a triangulated surface derived from 3D point data (X, Y, Z) representing existing ground, proposed grading, subsurface layers, or other irregular surfaces.
• Symbology Hierarchy:
  • Feature Definition ("What"): Defines the civil object type and links it to display and annotation rules.
  • Surface Feature Symbology ("How"): Dictates display behavior in plan, profile, and 3D views.
  • Element Template ("Why"): Specifies CAD properties—such as levels, colors, line styles, calculated features, source features, and annotation settings.

2. Source Feature Types

Terrain triangulation and boundaries are governed by specific source feature types:

• Breaklines & Soft Breaklines: Linear features that define elevation discontinuities and control triangulation edges.
• Spot Elevation Points: Discrete elevation points (X, Y, Z).
• Boundaries & Voids:
  • Holes: Internal areas excluded from triangulation.
  • Drape Boundaries & Drape Voids: Project boundaries or voids applied onto the surface.
  • Break Voids: Boundaries that create voids while enforcing breakline triangulation around the perimeter.
  • Islands: Un-triangulated areas inside internal voids.

3. Existing Complex Terrain Strategy

• Stable Element Identity: Base projects on a Complex Existing Terrain Model. Complex terrains maintain a stable element ID so downstream corridor rules continue referencing the same surface even if underlying source data is updated or exchanged.
• Delta / Null Terrain Workflow: When only a single existing terrain is provided, create a delta or null terrain by copying the existing surface to an elevation plane of zero. Combine the original surface and null terrain into a complex terrain to establish a stable reference target for corridor end conditions.

4. Combining Terrains: Append vs. Merge

• Append: Retains data from both terrain models, including overlapping areas. Use Append to expand the spatial coverage or supplement an existing terrain surface.
• Merge: Replaces the primary terrain data in overlapping regions with the secondary (merged) surface data. Use Merge when proposed design elevations must supersede existing ground elevations.

5. Clipped Terrain Workflow for Corridor Modeling

• Performance Optimization: Create a Clipped Terrain from the primary existing terrain using a closed boundary shape around the active design limits.
• Processing Savings: Trimming non-essential surface data significantly reduces triangle counts (e.g., from ~16,700 triangles down to ~1,700 triangles), allowing corridor end-condition target processing to execute faster.
• Dynamic Rule Preservation: The clipped terrain remains ruled to the source terrain and automatically updates if the clipping boundary shape is modified.

6. Proposed Terrain Creation: Static Meshes vs. Dynamic Graphical Filters

• Static Terrain (Design Meshes): Converts corridor design meshes into a static surface snapshot.
• Dynamic Terrain (Graphical Filters): Uses predefined graphical filters to select corridor features based on Feature Definitions, levels, or element types.
• Recommendation: Use Graphical Filters whenever maintaining a dynamic link to corridor changes is required, ensuring the proposed surface automatically updates as the corridor evolves.

7. Final Combined Surface Workflow

• Creating Final Surfaces: Build a final combined project terrain by setting the Complex Existing Terrain as the primary model and Merging the proposed project terrain into it.
• Result: Overlapping proposed points replace primary existing elevations, creating a clean, seamless surface for downstream design, volume calculations, and external export.

8. Batch Processing Updates

• Use Batch Processing routines to open and update design and terrain files in a structured sequence.
• Batch updating ensures changes correctly propagate through complex reference chains consisting of terrain models, corridor files, and container models.

9. Terrain File Storage and Placement

• Dedicated 3D DGN Files: Store each terrain model in its own dedicated 3D DGN file.

Avoid 2D File Creation: Creating a terrain inside a 2D file automatically generates a Default 3D model, which introduces unnecessary reference management complexity and makes terrain discovery difficult across-project surface discovery more difficult.