Track Builder - Basic Centers

Generates center road surface mesh geometry for track segments in the track builder system.

Overview

util_trackBuilder_basicCenters provides center road cross-section shapes (regular, flat, low, halfRegular) and compiles them into 3D mesh data. Uses a width-based LUT (look-up table) system so normals and vertices are precomputed per width step for performance.

Module path: lua/ge/extensions/util/trackBuilder/basicCenters.lua

Exports (M)

Internals

Available Shapes

Width-Based LUT System

Unlike borders (which use fixed-width shapes), center meshes vary width per point. The system precomputes vertex positions and normals for each discrete width step:

1. computeNormals(segment, shape) - scans segment points for min/max width.
2. For each needed width (in LUTDetail = 10 subdivisions per unit), computes:
   • Scaled vertex positions from cross-section points.
   • Smooth or sharp normals depending on crossPoints[i].sharp.
   • UV X coordinates relative to uvCenterIndex.
3. Cached in shape.vertexLUT[scaledWidth].

UV Mapping

• U axis: Distance along the cross-section from center, scaled by uv.width = 0.2.
• V axis: point.uvY * uv.height (along-track distance).

Each shape defines uvCenterIndex - indices whose UV X is treated as zero.

Mesh Compilation

compileMeshInfo(segment, shape):

1. For each quality-filtered point, looks up the LUT entry for the point's width.
2. Transforms vertices/normals into world space using the point's orientation.
3. Builds face indices connecting consecutive cross-sections.
4. Adds start/end caps if configured.

Quality Fallback

At quality level 4, all shapes fall back to low.

Output Format

{
  verts = {{x,y,z}, ...},
  uvs = {{u,v}, ...},
  normals = {{x,y,z}, ...},
  faces = {{v, n, u}, ...},
  material = "track_editor_A_center",
  tag = "center"
}

How It Works

1. Track builder assigns a centerMesh shape name to each segment.
2. getMeshes(segment) computes width-dependent normals, then compiles the mesh.
3. LUT caching means repeated widths are fast.
4. Call clearShapes() to reset caches when track parameters change.

Lua Examples

-- Used internally by track builder:
local centerMeshes = extensions.util_trackBuilder_basicCenters.getMeshes(segment)
-- Returns array: {centerMeshData}

-- Clear LUT cache after parameter changes
extensions.util_trackBuilder_basicCenters.clearShapes()

Additional Exports

• M.clearShapes - (undocumented)
• M.getMeshes - (undocumented)