thi-ng/umbrella

import type { Attribs, IHiccupShape2 } from "@thi.ng/geom-api";
import type { ReadonlyVec, Vec, VecPair } from "@thi.ng/vectors";
import { mixCubic } from "@thi.ng/vectors/mix-cubic";
import { __copyShape } from "../internal/copy.js";
import { __ensureNumVerts } from "../internal/pclike.js";
import { APC } from "./apc.js";

/**
 * nD Cubic bezier patch defined by array of 4x4 control points in this
 * order:
 *
 * ```text
 *           7   11
 *     3 +---+---+---+ 15 (UV = 1,1)
 *       |   |   |   |
 *     2 +---+---+---+ 14
 *       |   |   |   |
 *     1 +---+---+---+ 13
 *  v    |   |   |   |
 *  ^  0 +---+---+---+ 12
 *  |        4   8
 *  |
 *  +----> u
 * ```
 *
 * The class implements a `unmapPoint()` method to transform a 2D UV coordinate
 * into the worldspace position on the patch surface.
 *
 * The `toHiccup()` impl is only suitable for 2D patches.
 *
 * Ported from toxiclibs.
 *
 */
export class BPatch extends APC implements IHiccupShape2<BPatch> {
    readonly type = "bpatch";
    readonly dim = 2;

    constructor(points: Iterable<Vec>, attribs?: Attribs) {
        super(points, attribs);
        __ensureNumVerts(this.points.length, 16);
    }

    copy(): BPatch {
        return __copyShape(BPatch, this);
    }

    withAttribs(attribs: Attribs) {
        return new BPatch(this.points, attribs);
    }

    edges() {
        const p = this.points;
        return [
            [0, 1],
            [1, 2],
            [2, 3],
            [0, 4],
            [1, 5],
            [2, 6],
            [3, 7],
            [4, 5],
            [5, 6],
            [6, 7],
            [4, 8],
            [5, 9],
            [6, 10],
            [7, 11],
            [8, 9],
            [9, 10],
            [10, 11],
            [8, 12],
            [9, 13],
            [10, 14],
            [11, 15],
            [12, 13],
            [13, 14],
            [14, 15],
        ].map(([a, b]) => <VecPair>[p[a], p[b]]);
    }

    unmapPoint(uv: ReadonlyVec, out?: Vec) {
        const cp = this.points;
        const [u, v] = uv;
        return mixCubic(
            out || null,
            mixCubic([], cp[0], cp[4], cp[8], cp[12], v),
            mixCubic([], cp[1], cp[5], cp[9], cp[13], v),
            mixCubic([], cp[2], cp[6], cp[10], cp[14], v),
            mixCubic([], cp[3], cp[7], cp[11], cp[15], v),
            u
        );
    }

    toHiccup() {
        const attribs = this.attribs;
        const acc: any[] = ["g", { fill: "none", ...attribs }];
        if (attribs && attribs.res) {
            const res = attribs.res - 1;
            const delta = 1 / res;
            for (let u = 0; u <= res; u++) {
                const col = [];
                const row = [];
                const uu = u * delta;
                for (let v = 0; v <= res; v++) {
                    const p = [uu, v * delta];
                    col.push(this.unmapPoint(p));
                    row.push(this.unmapPoint([p[1], p[0]]));
                }
                acc.push(["polyline", {}, col]);
                acc.push(["polyline", {}, row]);
            }
        } else {
            this.edges().forEach((l) => acc.push(["line", {}, ...l]));
        }
        return acc;
    }
}