zine-runtime-utils.js

import * as THREE from 'three';
import {
  entranceExitWidth,
  entranceExitHeight,
  entranceExitDepth,
} from '../zine/zine-constants.js';

//

const localMatrix = new THREE.Matrix4();

//

export const getCapsuleIntersectionIndex = (
  entranceExitLocations,
  matrixWorld,
  position,
  capsuleRadius,
  capsuleHeight
) => {
  for (let i = 0; i < entranceExitLocations.length; i++) {
    const eel = entranceExitLocations[i];
    const boxQuaternion = new THREE.Quaternion().fromArray(eel.quaternion);
    const boxPosition = new THREE.Vector3().fromArray(eel.position)
      .add(new THREE.Vector3(0, entranceExitHeight / 2, entranceExitDepth / 2).applyQuaternion(
        boxQuaternion
      ));
    const boxSize = new THREE.Vector3(entranceExitWidth, entranceExitHeight, entranceExitDepth);
    localMatrix.compose(
      boxPosition,
      boxQuaternion,
      boxSize
    ).premultiply(matrixWorld).decompose(
      boxPosition,
      boxQuaternion,
      boxSize
    );

    const capsulePosition = position.clone().add(
      new THREE.Vector3(0, -capsuleHeight / 2, 0)
    );
    if (capsuleIntersectsBox(
      capsulePosition,
      capsuleRadius,
      capsuleHeight,
      boxPosition,
      boxQuaternion,
      boxSize,
    )) {
      return i;
    }
  }
  return -1;
};

// note: total height of the capsule is capsuleHeight + 2 * capsuleRadius
// the capsule is vertical, with capsulePosition in the center
// the distance from the center to the top and bottom is capsuleHeight / 2 + capsuleRadius
// check whether the given capsule intersects the given transformed box
export function capsuleIntersectsBox(
  capsulePosition,
  capsuleRadius,
  capsuleHeight,
  boxPosition,
  boxQuaternion,
  boxSize
) {
  // first, transform the capsule line into the box's local space
  const capsuleLine = new THREE.Line3(
    capsulePosition.clone().add(
      new THREE.Vector3(0, capsuleHeight / 2 + capsuleRadius, 0)
    ),
    capsulePosition.clone().add(
      new THREE.Vector3(0, -capsuleHeight / 2 - capsuleRadius, 0)
    )
  );
  capsuleLine.start.sub(boxPosition).applyQuaternion(boxQuaternion.clone().invert());
  capsuleLine.end.sub(boxPosition).applyQuaternion(boxQuaternion.clone().invert());
  // then, get the intersection in the box's local space
  return capsuleIntersectsAABB(
    capsuleLine,
    capsuleRadius,
    boxSize
  );
}
function capsuleIntersectsAABB(capsuleLine, capsuleRadius, boxSize) {
  const closestPointToCenter = capsuleLine.closestPointToPoint(
    new THREE.Vector3(0, 0, 0),
    true,
    new THREE.Vector3()
  );
  if (
    Math.abs(closestPointToCenter.x) <= boxSize.x / 2 + capsuleRadius &&
    Math.abs(closestPointToCenter.y) <= boxSize.y / 2 + capsuleRadius &&
    Math.abs(closestPointToCenter.z) <= boxSize.z / 2 + capsuleRadius
  ) {
    return true;
  } else {
    return false;
  }
}

export function makePromise() {
  let resolve, reject;
  const p = new Promise((a, r) => {
    resolve = a;
    reject = r;
  });
  p.resolve = resolve;
  p.reject = reject;
  return p;
}