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import { pointsClose, removeDuplicateEdges } from "../utils/geometry";
import { Grid } from "./grid";
import { scanCellWindow } from "./grid-scan";
import { findClosestEdgeInWindow, findClosestVertexInWindow } from "./grid-search";
// pointy-top, odd-r offset coordinates
export class HexagonGrid implements Grid {
constructor(private scale: number) {}
private axialToOffset(axial: { q: number; r: number }): {
col: number;
row: number;
} {
const col = axial.q + (axial.r - (axial.r & 1)) / 2;
const row = axial.r;
return { col, row };
}
pixelToCell(pixel: Point): { col: number; row: number } | null {
const tempQ =
((Math.sqrt(3) / 3) * pixel.x - (1 / 3) * pixel.y) / this.scale;
const tempR = ((2 / 3) * pixel.y) / this.scale;
const axial = this.axialRound({ q: tempQ, r: tempR, s: -tempQ - tempR });
return this.axialToOffset(axial);
}
private axialRound(frac: { q: number; r: number; s: number }): {
q: number;
r: number;
} {
let q = Math.round(frac.q);
let r = Math.round(frac.r);
const s = Math.round(frac.s);
const q_diff = Math.abs(q - frac.q);
const r_diff = Math.abs(r - frac.r);
const s_diff = Math.abs(s - frac.s);
if (q_diff > r_diff && q_diff > s_diff) {
q = -r - s;
} else if (r_diff > s_diff) {
r = -q - s;
}
return { q, r };
}
cellToPixel(cell: { col: number; row: number }): Point {
const hexSpacingX = this.scale * Math.sqrt(3);
const hexSpacingY = this.scale * 1.5;
const offsetX = (cell.row % 2) * (hexSpacingX / 2);
return { x: cell.col * hexSpacingX + offsetX, y: cell.row * hexSpacingY };
}
getNeighbors(cell: {
col: number;
row: number;
}): { col: number; row: number }[] {
const isOddRow = cell.row & 1;
const neighbors: { col: number; row: number }[] = [];
if (isOddRow) {
neighbors.push({ col: cell.col + 1, row: cell.row });
neighbors.push({ col: cell.col - 1, row: cell.row });
neighbors.push({ col: cell.col, row: cell.row - 1 });
neighbors.push({ col: cell.col + 1, row: cell.row - 1 });
neighbors.push({ col: cell.col, row: cell.row + 1 });
neighbors.push({ col: cell.col + 1, row: cell.row + 1 });
} else {
neighbors.push({ col: cell.col + 1, row: cell.row });
neighbors.push({ col: cell.col - 1, row: cell.row });
neighbors.push({ col: cell.col - 1, row: cell.row - 1 });
neighbors.push({ col: cell.col, row: cell.row - 1 });
neighbors.push({ col: cell.col - 1, row: cell.row + 1 });
neighbors.push({ col: cell.col, row: cell.row + 1 });
}
return neighbors;
}
getCellPolygon(cell: { col: number; row: number }): Point[] {
const center = this.cellToPixel(cell);
const points: Point[] = [];
for (let i = 0; i < 6; i++) {
const angle = (Math.PI / 3) * i + Math.PI / 6;
points.push({
x: center.x + this.scale * Math.cos(angle),
y: center.y + this.scale * Math.sin(angle),
});
}
return points;
}
getCellEdges(cell: { col: number; row: number }): EdgeInfo[] {
const poly = this.getCellPolygon(cell);
return poly.map((p, i) => ({
type: "edge",
points: [p, poly[(i + 1) % poly.length]],
}));
}
getEdgeAt(
pixel: Point,
threshold: number,
gridWidth: number,
gridHeight: number
): EdgeInfo | null {
const approxRow = Math.floor(pixel.y / (this.scale * 1.5));
const approxCol = Math.floor(pixel.x / (this.scale * Math.sqrt(3)));
return findClosestEdgeInWindow(
pixel,
threshold,
gridWidth,
gridHeight,
approxCol,
approxRow,
2,
2,
(cell) => this.getCellEdges(cell)
);
}
getVertexAt(
pixel: Point,
threshold: number,
gridWidth: number,
gridHeight: number
): Point | null {
const approxRow = Math.floor(pixel.y / (this.scale * 1.5));
const approxCol = Math.floor(pixel.x / (this.scale * Math.sqrt(3)));
return findClosestVertexInWindow(
pixel,
threshold,
gridWidth,
gridHeight,
approxCol,
approxRow,
2,
2,
(cell) => this.getCellPolygon(cell)
);
}
getEdgesAtVertex(
vertex: Point,
gridWidth: number,
gridHeight: number
): EdgeInfo[] {
const edges: EdgeInfo[] = [];
const epsilon = 0.1;
// For simplicity, search around the vertex
const approxRow = Math.floor(vertex.y / (this.scale * 1.5));
const approxCol = Math.floor(vertex.x / (this.scale * Math.sqrt(3)));
scanCellWindow(gridWidth, gridHeight, approxCol, approxRow, 2, 2, (c, r) => {
const cellEdges = this.getCellEdges({ col: c, row: r });
for (const edge of cellEdges) {
if (
pointsClose(vertex, edge.points[0], epsilon) ||
pointsClose(vertex, edge.points[1], epsilon)
) {
edges.push(edge);
}
}
});
return removeDuplicateEdges(edges);
}
}
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