freesewing/src/utils.js

import Point from "./point";
import Bezier from "bezier-js";

/** Returns internal hook name for a macro */
export function macroName(name) {
  return `_macro_${name}`;
}

/** Find intersection of two (endless) lines */
export function beamsIntersect(a1, a2, b1, b2) {
  let slopeA = a1.slope(a2);
  let slopeB = b1.slope(b2);
  if (slopeA === slopeB) return false; // Parallel lines

  if (a1.x === a2.x)
    return new Point(a1.x, slopeB * a1.x + (b1.y - slopeB * b1.x));
  // Vertical line A
  else if (b1.x === b2.x)
    return new Point(b1.x, slopeA * b1.x + (a1.y - slopeA * a1.x));
  // Vertical line B
  else {
    // Swap points if line A or B goes from right to left
    if (a1.x > a2.x) a1 = a2.copy();
    if (b1.x > b2.x) b1 = b2.copy();
    // Find y intercept
    let iA = a1.y - slopeA * a1.x;
    let iB = b1.y - slopeB * b1.x;

    // Find intersection
    let x = (iB - iA) / (slopeA - slopeB);
    let y = slopeA * x + iA;

    return new Point(x, y);
  }
}

/** Find intersection of two line segments */
export function linesIntersect(a1, a2, b1, b2) {
  let p = beamsIntersect(a1, a2, b1, b2);
  if (!p) return false;
  let lenA = a1.dist(a2);
  let lenB = b1.dist(b2);
  let lenC = a1.dist(p) + p.dist(a2);
  let lenD = b1.dist(p) + p.dist(b2);
  if (
    Math.round(lenA) == Math.round(lenC) &&
    Math.round(lenB) == Math.round(lenD)
  )
    return p;
  else return false;
}

/** Finds out whether a point lies on an endless line */
export function pointOnBeam(from, to, check, precision = 1e6) {
  if (from.sitsOn(check)) return true;
  if (to.sitsOn(check)) return true;
  let cross = check.dx(from) * to.dy(from) - check.dy(from) * to.dx(from);

  if (Math.abs(Math.round(cross * precision) / precision) === 0) return true;
  else return false;
}

/** Finds out whether a point lies on a line segment */
export function pointOnLine(from, to, check, precision = 1e6) {
  if (!pointOnBeam(from, to, check, precision)) return false;
  let lenA = from.dist(to);
  let lenB = from.dist(check) + check.dist(to);
  if (Math.round(lenA) == Math.round(lenB)) return true;
  else return false;
}

/** Finds out whether a point lies on a curve */
export function pointOnCurve(start, cp1, cp2, end, check) {
  if (start.sitsOn(check)) return true;
  if (end.sitsOn(check)) return true;
  let curve = new Bezier(
    { x: start.x, y: start.y },
    { x: cp1.x, y: cp1.y },
    { x: cp2.x, y: cp2.y },
    { x: end.x, y: end.y }
  );
  let intersections = curve.intersects({
    p1: { x: check.x - 1, y: check.y },
    p2: { x: check.x + 1, y: check.y }
  });
  if (intersections.length > 0) return intersections.shift();
  else return false;
}

/** Find where an (endless) line intersects with a certain X-value */
export function beamIntersectsX(from, to, x) {
  if (from.x === to.x) return false; // Vertical line
  let top = new Point(x, -10);
  let bottom = new Point(x, 10);

  return beamsIntersect(from, to, top, bottom);
}

/** Find where an (endless) line intersects with a certain Y-value */
export function beamIntersectsY(from, to, y) {
  if (from.y === to.y) return false; // Horizontal line
  let left = new Point(-10, y);
  let right = new Point(10, y);

  return beamsIntersect(from, to, left, right);
}

/** Convert value in mm to cm or imperial units */
export function units(value, to = "metric") {
  if (to === "imperial") return round(value / 25.4) + '"';
  else return round(value / 10) + "cm";
}

/** Find where a curve intersects with line */
export function lineIntersectsCurve(start, end, from, cp1, cp2, to) {
  let intersections = [];
  let bz = new Bezier(
    { x: from.x, y: from.y },
    { x: cp1.x, y: cp1.y },
    { x: cp2.x, y: cp2.y },
    { x: to.x, y: to.y }
  );
  let line = {
    p1: { x: start.x, y: start.y },
    p2: { x: end.x, y: end.y }
  };
  for (let t of bz.intersects(line)) {
    let isect = bz.get(t);
    intersections.push(new Point(isect.x, isect.y));
  }

  if (intersections.length === 0) return false;
  else if (intersections.length === 1) return intersections[0];
  else return intersections;
}

/** Find where a curve intersects with another curve */
export function curvesIntersect(
  fromA,
  cp1A,
  cp2A,
  toA,
  fromB,
  cp1B,
  cp2B,
  toB
) {
  let precision = 0.005; // See https://github.com/Pomax/bezierjs/issues/99
  let intersections = [];
  let curveA = new Bezier(
    { x: fromA.x, y: fromA.y },
    { x: cp1A.x, y: cp1A.y },
    { x: cp2A.x, y: cp2A.y },
    { x: toA.x, y: toA.y }
  );
  let curveB = new Bezier(
    { x: fromB.x, y: fromB.y },
    { x: cp1B.x, y: cp1B.y },
    { x: cp2B.x, y: cp2B.y },
    { x: toB.x, y: toB.y }
  );

  for (let tvalues of curveA.intersects(curveB, precision)) {
    let intersection = curveA.get(tvalues.substr(0, tvalues.indexOf("/")));
    intersections.push(new Point(intersection.x, intersection.y));
  }

  if (intersections.length === 0) return false;
  else if (intersections.length === 1) return intersections.shift();
  else {
    let unique = [];
    for (let i of intersections) {
      let dupe = false;
      for (let u of unique) {
        if (i.sitsRoughlyOn(u)) dupe = true;
      }
      if (!dupe) unique.push(i);
    }
    return unique;
  }
}

/** Find the intersections between two circles */
export function circlesIntersect(c1, r1, c2, r2, sort = "x") {
  let dx = c1.dx(c2);
  let dy = c1.dy(c2);
  let dist = c1.dist(c2);
  // Check for edge cases
  if (dist > parseFloat(r1) + parseFloat(r2)) return false; // Circles do not intersect
  if (dist < parseFloat(r2) - parseFloat(r1)) return false; // One circle is contained in the other
  if (dist === 0 && r1 === r2) return false; // Two circles are identical
  let chorddistance =
    (Math.pow(r1, 2) - Math.pow(r2, 2) + Math.pow(dist, 2)) / (2 * dist);
  let halfchordlength = Math.sqrt(Math.pow(r1, 2) - Math.pow(chorddistance, 2));
  let chordmidpointx = c1.x + (chorddistance * dx) / dist;
  let chordmidpointy = c1.y + (chorddistance * dy) / dist;
  let i1 = new Point(
    chordmidpointx + (halfchordlength * dy) / dist,
    chordmidpointy - (halfchordlength * dx) / dist
  );
  let i2 = new Point(
    chordmidpointx - (halfchordlength * dy) / dist,
    chordmidpointy + (halfchordlength * dx) / dist
  );

  if ((sort === "x" && i1.x <= i2.x) || (sort === "y" && i1.y <= i2.y))
    return [i1, i2];
  else return [i2, i1];
}

/** Find the intersections between a beam and a circle */
export function beamIntersectsCircle(c, r, p1, p2, sort = "x") {
  let dx = p2.x - p1.x;
  let dy = p2.y - p1.y;
  let A = Math.pow(dx, 2) + Math.pow(dy, 2);
  let B = 2 * (dx * (p1.x - c.x) + dy * (p1.y - c.y));
  let C = Math.pow(p1.x - c.x, 2) + Math.pow(p1.y - c.y, 2) - Math.pow(r, 2);

  let det = Math.pow(B, 2) - 4 * A * C;

  if (A <= 0.0000001 || det < 0) return false;
  // No real solutions
  else if (det === 0) {
    // One solution
    let t = (-1 * B) / (2 * A);
    let i1 = new Point(p1.x + t * dx, p1.y + t * dy);
    return [i1];
  } else {
    // Two solutions
    let t = (-1 * B + Math.sqrt(det)) / (2 * A);
    let i1 = new Point(p1.x + t * dx, p1.y + t * dy);
    t = (-1 * B - Math.sqrt(det)) / (2 * A);
    let i2 = new Point(p1.x + t * dx, p1.y + t * dy);
    if ((sort === "x" && i1.x <= i2.x) || (sort === "y" && i1.y <= i2.y))
      return [i1, i2];
    else return [i2, i1];
  }
}
/** Find the intersections between a line and a circle */
export function lineIntersectsCircle(c, r, p1, p2, sort = "x") {
  let intersections = beamIntersectsCircle(c, r, p1, p2, sort);
  if (intersections === false) return false;
  else {
    if (intersections.length === 1) {
      if (pointOnLine(p1, p2, intersections[0])) return intersections;
      else return false;
    } else {
      let i1 = intersections[0];
      let i2 = intersections[1];
      if (!pointOnLine(p1, p2, i1, 5) && !pointOnLine(p1, p2, i2, 5))
        return false;
      else if (pointOnLine(p1, p2, i1, 5) && pointOnLine(p1, p2, i2, 5)) {
        if ((sort === "x" && i1.x <= i2.x) || (sort === "y" && i1.y <= i2.y))
          return [i1, i2];
        else return [i2, i1];
      } else if (pointOnLine(p1, p2, i1, 5)) return [i1];
      else if (pointOnLine(p1, p2, i2, 5)) return [i2];
    }
  }
}

export function curveEdge(curve, edge, steps = 500) {
  let x = Infinity;
  let y = Infinity;
  let p;
  if (edge === "bottom") y = -Infinity;
  if (edge === "right") x = -Infinity;
  for (let i = 0; i < steps; i++) {
    p = curve.get(i / steps);
    if (
      (edge === "top" && p.y < y) ||
      (edge === "bottom" && p.y > y) ||
      (edge === "right" && p.x > x) ||
      (edge === "left" && p.x < x)
    ) {
      x = p.x;
      y = p.y;
    }
  }

  return new Point(x, y);
}

/**
 * Calculates scale factor based on stretch factor
 *
 * The way people measure stretch intuitively is
 * different from the way we handle stretch in code.
 * When people say '25% stretch' they mean that
 * 10cm fabric should get stretched to 12.5cm fabric.
 * In our code, that means we need to scale things by 80%.
 *
 * This method does that calculation.
 */
export function stretchToScale(stretch) {
  return 1 / (1 + parseFloat(stretch));
}

export function round(value) {
  return Math.round(value * 1e2) / 1e2;
}