mesh v2 at /v2/mesh

src2/geo/points.js

@@ -0,0 +1,128 @@
+/** Copyright Stewart Allen <sa@grid.space> -- All Rights Reserved */
+
+"use strict";
+
+import { newPoint } from '../geo/point.js';
+
+const { config } = base;
+
+/**
+ * converts a geometry point array into a kiri point array
+ * with optional decimation
+ */
+export function verticesToPoints(array, options) {
+    let parr = new Array(array.length / 3),
+        i = 0,
+        j = 0,
+        t = Date.now(),
+        hash = {},
+        unique = 0,
+        passes = 0,
+        points,
+        oldpoints = parr.length,
+        newpoints;
+
+    let {threshold, precision, maxpass} = options || {};
+    // threshold = point count for triggering decimation
+    // precision = under which points are merged
+    // maxpass = max number of decimations
+    threshold = threshold > 0 ? threshold : config.decimate_threshold;
+    precision = precision >= 0 ? precision : config.precision_decimate;
+    maxpass = maxpass >= 0 ? maxpass : 0;
+
+    // replace point objects with their equivalents
+    if (maxpass) {
+        while (i < array.length) {
+            let p = newPoint(array[i++], array[i++], array[i++]),
+                k = p.key,
+                m = hash[k];
+            if (!m) {
+                m = p;
+                hash[k] = p;
+                unique++;
+            }
+            parr[j++] = m;
+        }
+    } else {
+        while (i < array.length) {
+            parr[j++] = newPoint(array[i++], array[i++], array[i++]);
+        }
+    }
+
+    // decimate until all point spacing > precision
+    if (maxpass && precision > 0.0)
+    while (parr.length > threshold) {
+        let lines = [], line, dec = 0;
+        for (i=0; i<oldpoints; ) {
+            let p1 = parr[i++],
+                p2 = parr[i++],
+                p3 = parr[i++];
+            lines.push( {p1:p1, p2:p2, d:Math.sqrt(p1.distToSq3D(p2))} );
+            lines.push( {p1:p1, p2:p3, d:Math.sqrt(p1.distToSq3D(p3))} );
+            lines.push( {p1:p2, p2:p3, d:Math.sqrt(p2.distToSq3D(p3))} );
+        }
+        // sort by ascending line length
+        lines.sort(function(a,b) {
+            return a.d - b.d
+        });
+        // create offset mid-points
+        for (i=0; i<lines.length; i++) {
+            line = lines[i];
+            // skip lines longer than precision threshold
+            if (line.d >= precision) break;
+            // skip lines where one of the points is already offset
+            if (line.p1.op || line.p2.op) continue;
+            // todo skip dropping lines where either point is a "sharp" on 3 vectors
+            // todo skip dropping lines where either point connects to a "long" line
+            line.p1.op = line.p2.op = line.p1.midPointTo3D(line.p2);
+            dec++;
+        }
+        // exit if nothing to decimate
+        if (dec === 0) break;
+        passes++;
+        // create new facets
+        points = new Array(oldpoints);
+        newpoints = 0;
+        for (i=0; i<oldpoints; ) {
+            let p1 = parr[i++],
+                p2 = parr[i++],
+                p3 = parr[i++];
+            // drop facets with two offset points
+            if (p1.op && p1.op === p2.op) continue;
+            if (p1.op && p1.op === p3.op) continue;
+            if (p2.op && p2.op === p3.op) continue;
+            // otherwise emit altered facet
+            points[newpoints++] = p1.op || p1;
+            points[newpoints++] = p2.op || p2;
+            points[newpoints++] = p3.op || p3;
+        }
+        parr = points.slice(0,newpoints);
+        oldpoints = newpoints;
+        if (passes >= maxpass) {
+            break;
+        }
+    }
+
+    // if (passes) console.trace({passes, threshold, precision, maxpass});
+
+    if (passes) console.log({
+        before: array.length / 3,
+        after: parr.length,
+        unique: unique,
+        decimations: passes,
+        time: (Date.now() - t)
+    });
+
+    return parr;
+}
+
+export function pointsToVertices(points) {
+    let vertices = new Float32Array(points.length * 3),
+        i = 0, vi = 0;
+    while (i < points.length) {
+        vertices[vi++] = points[i].x;
+        vertices[vi++] = points[i].y;
+        vertices[vi++] = points[i++].z;
+    }
+    return vertices;
+}