@davepagurek/flo-mat/src/mat/simplify-mat.ts

Medial / Scale Axis Transform (MAT/SAT) Library.

import { hausdorffDistance } from 'flo-bezier3';
import { CpNode, getCpNodesOnCircle, isTerminating, removeCpNode } from '../cp-node/cp-node.js';
import { getBranches } from './get-branches.js';
import { getCurveToNext } from '../cp-node/get-curve-to-next.js';
import { getCurveBetween } from '../get-curve/get-curve-between.js';
import { Mat } from './mat.js';


/**
 * Simplifies the given MAT by replacing the piecewise quad beziers composing 
 * the MAT with fewer ones to within a given tolerance.
 * @param cpNode A representation of the MAT
 * @param anlgeTolerance Tolerance given as the degrees difference of the unit 
 * direction vectors at the interface between curves. A tolerance of zero means
 * perfect smoothness is required - defaults to 15.
  * @param hausdorffTolerance The approximate maximum Hausdorff Distance tolerance -
 * defaults to `2**-3`
 * @param maxIterations The max iterations, defaults to `50`
 */
function simplifyMat(
        mat: Mat,
        anlgeTolerance = 15,
        hausdorffTolerance = 2**-3,
        maxIterations = 50): Mat {

    let cpNode = mat.cpNode;
    
    // Start from a leaf
    while (!isTerminating(cpNode)) { cpNode = cpNode.next; }

    const branches = getBranches(cpNode, anlgeTolerance);

    const canDeletes: CpNode[] = [];
    for (let k=0; k<branches.length; k++) {
        const branch = branches[k];

        // Try to remove some
        let j = 0;
        while (j < branch.length) {
            const i = j;
            while (true) {
                j++;

                if (j === branch.length) { break; }

                const hd = getTotalHausdorffDistance(i, j, branch, maxIterations);

                if (hd > hausdorffTolerance) {
                    break;
                } else {
                    canDeletes.push(branch[j]);
                }
            }

            if (i+1 === j) { 
                // no simplification occured
                break;
            }
        }
    }

    for (const cpNode of canDeletes) {
        const isTerminating_ = isTerminating(cpNode);
        const onCircleCount = getCpNodesOnCircle(cpNode).length;
        if (isTerminating_ || onCircleCount !== 2) { 
            continue; 
        }

        removeCpNode(cpNode);
    }
    
    //return { cpNode, cpTrees: createNewCpTree(cpNode) }; 
    return { cpNode, cpTrees: undefined! }; 
}


function getTotalHausdorffDistance(
        i: number, 
        j: number, 
        branch: CpNode[],
        hausdorffSpacing: number) {

    const hds: number[] = [];
    const longCurve = getCurveBetween(branch[i], branch[j].next);
    for (; i<j+1; i++) {
        hds.push(hausdorffDistance(
            getCurveToNext(branch[i]),
            longCurve,
            hausdorffSpacing
        ));
    }

    return Math.max(...hds);
}


export { simplifyMat }