Road Architect - Terraform

local terraform = require('editor/tech/roadArchitect/terraform')

-- Conform terrain to a single road (index 3, DOI=100m, margin=5m)
terraform.conformTerrainToRoad(3, 100, 5)

-- Terraform all roads in a group
terraform.terraformMultiRoads(150, 7, roadGroup)

-- Export/import heightmap
terraform.writeHeightmapToPng('/temp/heightmap.png')
terraform.setHeightmapFromPng('/temp/heightmap.png')

-- Get road masks for painting/analysis
local roadMask, marginMask = terraform.getRoadMasks(100, 5, group)

-- Algorithm overview:
-- 1. Compute road quads from renderData (top surface, excluding tunnels)
-- 2. Build kd-tree of quads for fast point-in-quad queries
-- 3. For each grid point, test intersection with quads using barycentric coords
-- 4. Build fixed mask (directly under road) and dilate with blending
-- 5. Iteratively smooth using separable box filter (X then Y passes)
-- 6. Number of iterations: ceil(0.5 * sqrt(8*DOI + 1) - 1)
-- 7. Average mask edges, then apply final height changes with undo/redo

-- Undo/redo support:
-- History stores {old, new, x, y} for each modified grid cell
-- Uses editor.history:commitAction("Terraform", ...)

-- Bilinear interpolation for quad intersection:
-- Uses p:invBilinear2D(q1, q2, q3, q4) to get (u,v)
-- Height = lerp(lerp(q1.z, q2.z, u), lerp(q3.z, q4.z, u), v)