export/buildSimMap

Produces a downsampled ApolloMap for Dreamview visualization, porting sim_map_generator.cc.

buildSimMap

function buildSimMap(baseMap: ApolloMap): ApolloMap

Takes a fully-built base map and returns a new ApolloMap with:

• All lane curves downsampled (fewer points)
• left_sample, right_sample, left_road_sample, right_road_sample removed from all lanes
• All non-lane elements preserved unchanged

Example

const base = await buildBaseMap(state)
const sim = buildSimMap(base)
const bytes = await encodeMap(sim)
downloadBinary(bytes, 'sim_map.bin')

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downsampleByAngle

function downsampleByAngle(
  points: number[][],
  threshold?: number // default: Math.PI / 180 (1°)
): number[][]

Removes intermediate points whose bearing change from the previous to the next point is below threshold. Always keeps the first and last point.

Algorithm (from points_downsampler.h)

for i in 1..n-2:
  delta_heading = |bearing(points[i-1]→points[i]) - bearing(points[i]→points[i+1])|
  if delta_heading >= threshold: keep points[i]

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downsampleByDistance

function downsampleByDistance(
  points: number[][],
  normalInterval?: number, // default: 5 m
  steepInterval?: number // default: 1 m
): number[][]

Keeps one point per normalInterval meters. On steep curves (heading change > π/4 = 45°), uses steepInterval instead to preserve curve fidelity.

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Application scope

Both passes are applied to every CurveSegment.lineSegment.point[] in:

• lane.central_curve
• lane.left_boundary.curve
• lane.right_boundary.curve

This reduces the point count of a typical city-driving lane from ~100+ points (1 m sampling) to ~20–30 points, significantly reducing the sim_map file size and Dreamview rendering load.