Fantasy-Map-Generator/procedural/docs/findGridCell.md

Looking more carefully at the code flow:

1. findGridCell vs Voronoi Cell Indices

The key insight is that findGridCell in graphUtils.js:100-105 is used for coordinate-to-grid mapping, but the actual iteration in heightmap-generator.js happens over different indices.

2. Actual Iteration Patterns

In heightmap-generator.js, the problematic iterations are:

• Line 165: for (const c of grid.cells.c[q]) - but q comes from queue.shift() where queue starts with [start]
• Line 209: grid.cells.c[q].forEach(...) - same pattern
• Line 268: grid.cells.c[cur].forEach(...) - cur is tracked through valid cell traversal
• Line 516: grid.cells.c[i].forEach(...) - i is the map index over heights

3. The Critical Constraint

Looking at voronoi.js:22-27, cells.c[p] is only populated when: if (p < this.pointsN && !this.cells.c[p]) { // populate cells.c[p] }

4. Why No Errors Occur

The code works because:

1. heights array length matches valid cells: In the original ../modules/heightmap-generator.js:11, heights is created with length: points.length, which equals pointsN

const setGraph = graph => {
const {cellsDesired, cells, points} = graph;
heights = cells.h ? Uint8Array.from(cells.h) : createTypedArray({maxValue: 100, length: points.length});
blobPower = getBlobPower(cellsDesired);
linePower = getLinePower(cellsDesired);
grid = graph;
};

1. Queue propagation stays within bounds: When iterating grid.cells.c[q], the q values come from: - Initial valid starting points from findGridCell - Subsequent values from grid.cells.c[previous_q] which only contains valid adjacent cell indices
2. Voronoi adjacency constraint: The cells.c[p] arrays only contain indices of valid neighboring cells (< pointsN), so the iteration naturally stays within the populated sparse array bounds
3. Map iteration bounds: In line 468's heights.map((h, i) => ...), i ranges from 0 to heights.length-1, which equals pointsN-1, so grid.cells.c[i] is always within the populated range.

The sparse array works because the algorithm's traversal patterns are naturally constrained to only access indices that were populated during Voronoi construction.

TASKS

1. analyze ../modules heightmap-generator.js and src/engine/modules/heightmap-generator.js to determine why the logic has deviated. Produce docs/HEIGHTMAP_ASSESSMENT.md with findings and recommendations