bowling-analysis-system/src/bowling_analysis/metrics/calculations/PositionCalculations.js

A comprehensive system for analyzing bowling techniques using video processing and metrics calculation

/**
 * @fileoverview Position calculations for bowling analysis
 * @module PositionCalculations
 */

/**
 * Calculates the center of mass from pose landmarks
 * @param {Array<Object>} landmarks - Array of pose landmarks
 * @returns {Object|null} Center of mass coordinates or null if calculation fails
 */
function calculateCenterOfMass(landmarks) {
  if (!Array.isArray(landmarks) || landmarks.length === 0) return null;
  
  // Get key landmarks
  const nose = landmarks.find(l => l.index === 0);
  const leftShoulder = landmarks.find(l => l.index === 11);
  const rightShoulder = landmarks.find(l => l.index === 12);
  const leftHip = landmarks.find(l => l.index === 23);
  const rightHip = landmarks.find(l => l.index === 24);
  
  if (!nose || !leftShoulder || !rightShoulder || !leftHip || !rightHip) return null;
  
  // Calculate midpoints
  const shoulderMidpoint = {
    x: (leftShoulder.x + rightShoulder.x) / 2,
    y: (leftShoulder.y + rightShoulder.y) / 2,
    z: (leftShoulder.z + rightShoulder.z) / 2
  };
  
  const hipMidpoint = {
    x: (leftHip.x + rightHip.x) / 2,
    y: (leftHip.y + rightHip.y) / 2,
    z: (leftHip.z + rightHip.z) / 2
  };
  
  // Calculate weighted average for center of mass
  // Head: 8%, Upper body: 52%, Lower body: 40%
  return {
    x: nose.x * 0.08 + shoulderMidpoint.x * 0.52 + hipMidpoint.x * 0.40,
    y: nose.y * 0.08 + shoulderMidpoint.y * 0.52 + hipMidpoint.y * 0.40,
    z: nose.z * 0.08 + shoulderMidpoint.z * 0.52 + hipMidpoint.z * 0.40
  };
}

/**
 * Calculates the shoulder width from pose landmarks
 * @param {Array<Object>} landmarks - Array of pose landmarks
 * @returns {number|null} Shoulder width in units or null if calculation fails
 */
function calculateShoulderWidth(landmarks) {
  if (!Array.isArray(landmarks) || landmarks.length === 0) return null;
  
  const leftShoulder = landmarks.find(l => l.index === 11);
  const rightShoulder = landmarks.find(l => l.index === 12);
  
  if (!leftShoulder || !rightShoulder) return null;
  
  return Math.sqrt(
    Math.pow(rightShoulder.x - leftShoulder.x, 2) + 
    Math.pow(rightShoulder.y - leftShoulder.y, 2) + 
    Math.pow(rightShoulder.z - leftShoulder.z, 2)
  );
}

/**
 * Calculates the hip width from pose landmarks
 * @param {Array<Object>} landmarks - Array of pose landmarks
 * @returns {number|null} Hip width in units or null if calculation fails
 */
function calculateHipWidth(landmarks) {
  if (!Array.isArray(landmarks) || landmarks.length === 0) return null;
  
  const leftHip = landmarks.find(l => l.index === 23);
  const rightHip = landmarks.find(l => l.index === 24);
  
  if (!leftHip || !rightHip) return null;
  
  return Math.sqrt(
    Math.pow(rightHip.x - leftHip.x, 2) + 
    Math.pow(rightHip.y - leftHip.y, 2) + 
    Math.pow(rightHip.z - leftHip.z, 2)
  );
}

/**
 * Calculates the torso length from pose landmarks
 * @param {Array<Object>} landmarks - Array of pose landmarks
 * @returns {number|null} Torso length in units or null if calculation fails
 */
function calculateTorsoLength(landmarks) {
  if (!Array.isArray(landmarks) || landmarks.length === 0) return null;
  
  // Get midpoints of shoulders and hips
  const leftShoulder = landmarks.find(l => l.index === 11);
  const rightShoulder = landmarks.find(l => l.index === 12);
  const leftHip = landmarks.find(l => l.index === 23);
  const rightHip = landmarks.find(l => l.index === 24);
  
  if (!leftShoulder || !rightShoulder || !leftHip || !rightHip) return null;
  
  const shoulderMidpoint = {
    x: (leftShoulder.x + rightShoulder.x) / 2,
    y: (leftShoulder.y + rightShoulder.y) / 2,
    z: (leftShoulder.z + rightShoulder.z) / 2
  };
  
  const hipMidpoint = {
    x: (leftHip.x + rightHip.x) / 2,
    y: (leftHip.y + rightHip.y) / 2,
    z: (leftHip.z + rightHip.z) / 2
  };
  
  return Math.sqrt(
    Math.pow(shoulderMidpoint.x - hipMidpoint.x, 2) + 
    Math.pow(shoulderMidpoint.y - hipMidpoint.y, 2) + 
    Math.pow(shoulderMidpoint.z - hipMidpoint.z, 2)
  );
}

module.exports = {
  calculateCenterOfMass,
  calculateShoulderWidth,
  calculateHipWidth,
  calculateTorsoLength
};