Press n or j to go to the next uncovered block, b, p or k for the previous block.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | import { vec3 } from 'gl-matrix'; import { Types } from '@cornerstonejs/core'; function _getAreaVector(polyline: Types.Point3[]): Types.Point3 { const vecArea = vec3.create(); // Reference point can be any point on the same plane const refPoint = polyline[0]; // Takes three points, reference point and two other points from each line // segment, and calculate the area with cross product. The magnitude of the // vector returned by a cross product is equal to the area of the parallelogram // that the vectors span which is two times the area of the triangle. // // Not calling vec3 mathods makes the function run much faster since polylines // may have thousands of points when using freehand ROI tool and that would // increase considerably the number of function calls. for (let i = 0, len = polyline.length; i < len; i++) { const p1 = polyline[i]; // Using ternary instead of % (mod) operator to make it faster const p2Index = i === len - 1 ? 0 : i + 1; const p2 = polyline[p2Index]; const aX = p1[0] - refPoint[0]; const aY = p1[1] - refPoint[1]; const aZ = p1[2] - refPoint[2]; const bX = p2[0] - refPoint[0]; const bY = p2[1] - refPoint[1]; const bZ = p2[2] - refPoint[2]; // Cross product without calling vec3.cross() for better performance vecArea[0] += aY * bZ - aZ * bY; vecArea[1] += aZ * bX - aX * bZ; vecArea[2] += aX * bY - aY * bX; } // Divide by two because cross product returns two times the area for each triangle vec3.scale(vecArea, vecArea, 0.5); // The magnitude of the vector is the area of the polyline return <Types.Point3>vecArea; } /** * Calculate the normal of a 3D planar polyline * @param polyline - Planar polyline in 3D space * @returns Normal of the 3D planar polyline */ export default function getNormal3(polyline: Types.Point3[]): Types.Point3 { const vecArea = _getAreaVector(polyline); return vec3.normalize(vecArea, vecArea) as Types.Point3; } |