From 0349ea516903591c23f00e1b39875a417ea15adb Mon Sep 17 00:00:00 2001
From: Stewart Allen <sa@grid.space>
Date: Wed, 24 Sep 2025 23:59:31 -0400
Subject: [PATCH] add basic thin wall handling and default to on

---
 src/kiri/core/conf.js     |  2 +-
 src/kiri/core/consts.js   |  1 +
 src/kiri/core/print.js    | 17 ++++++----
 src/kiri/mode/fdm/post.js | 71 +++++++++++++++++----------------------
 4 files changed, 44 insertions(+), 47 deletions(-)

diff --git a/src/kiri/core/conf.js b/src/kiri/core/conf.js
index 3153c01f..febd09c0 100644
--- a/src/kiri/core/conf.js
+++ b/src/kiri/core/conf.js
@@ -338,7 +338,7 @@ export const conf = {
                 outputLoops: 0,
                 outputInvertX: false,
                 outputInvertY: false,
-                sliceDetectThin: "off",
+                sliceDetectThin: "basic",
                 sliceMinHeight: 0,
                 sliceAdaptive: false,
                 zHopDistance: 0.2,
diff --git a/src/kiri/core/consts.js b/src/kiri/core/consts.js
index 748fa4e4..fa73787f 100644
--- a/src/kiri/core/consts.js
+++ b/src/kiri/core/consts.js
@@ -115,6 +115,7 @@ const LISTS = {
     ],
     thin: [
         { name: "off" },
+        { name: "basic" },
         { name: "adaptive" },
         { name: "legacy 1" },
         { name: "legacy 2" }
diff --git a/src/kiri/core/print.js b/src/kiri/core/print.js
index 7b6c642c..c343540b 100644
--- a/src/kiri/core/print.js
+++ b/src/kiri/core/print.js
@@ -137,18 +137,21 @@ class Print {
             printSpeed = minSpeed + (printSpeed - minSpeed) * (perimeter / process.outputShortPoly);
         }
 
+        let lpo;
         poly.forEachPoint((point, pos, points, count) => {
-            if (first || point.skip) {
+            if (point.skip && lpo?.skip) {
+                scope.addOutput(output, point, 0, moveSpeed, tool);
+            } else if (first) {
                 // if (point.skip) console.log({ skip: point });
-                if (first && options.onfirst) {
+                if (options.onfirst) {
                     options.onfirst(point);
                 }
                 // move to first output point on poly
                 let out = scope.addOutput(output, point, 0, moveSpeed, tool);
-                if (first && options.onfirstout) {
+                if (options.onfirstout) {
                     options.onfirstout(out);
                 }
-                if (first) first = false;
+                first = false;
             } else {
                 let seglen = last.distTo2D(point);
                 if (coastDist && shellMult && perimeter - seglen <= coastDist) {
@@ -159,10 +162,12 @@ class Print {
                     shellMult = 0;
                 }
                 perimeter -= seglen;
+                // increase mult by % of point moved relative to nozzle radius
+                let multOut = shellMult + (point.moved ?? 0);
                 // to increase shellMult when point.inc set for collapsed points
-                scope.addOutput(output, point, shellMult, printSpeed, tool);
+                scope.addOutput(output, point, multOut, printSpeed, tool);
             }
-            last = point;
+            last = lpo = point;
         }, close, closest.index);
 
         this.lastPoly = poly;
diff --git a/src/kiri/mode/fdm/post.js b/src/kiri/mode/fdm/post.js
index 8da695bb..68da6933 100644
--- a/src/kiri/mode/fdm/post.js
+++ b/src/kiri/mode/fdm/post.js
@@ -7,6 +7,7 @@ import { polygons as POLY, fillArea } from '../../../geo/polygons.js';
 import { getRangeParameters } from './driver.js';
 import { slicer } from '../../../geo/slicer.js';
 import { Point } from '../../../geo/point.js';
+import { Slope } from '../../../geo/slope.js';
 
 slicer.slicePost.FDM = slicePost;
 
@@ -69,7 +70,7 @@ export function slicePost(data, options) {
 };
 
 function offset_default(params) {
-    let { z, top, count, top_poly, offset1, offsetN, wasm, last, gaps } = params;
+    let { z, top, count, top_poly, offset1, offsetN, wasm, last, gaps, thin } = params;
 
     let first;
 
@@ -104,16 +105,31 @@ function offset_default(params) {
         }
     );
 
+    if (!thin) {
+        return { last, gaps };
+    }
+
+    const deltaBig = 160;
+    const deltSmall = 20;
+
     // look for close points on adjacent segmented polys and merge
     let test_polys = first !== last ? [ ...first, ...last ] : last;
-    let thin_test = POLY.flatten(test_polys).map(poly => {
+    let test_flats = POLY.flatten(test_polys);
+
+    // pre-compute segment angles
+    for (let poly of test_flats)
+    poly.forEachSegment((p0, p1) => {
+        p0.angle = new Slope(p0, p1);
+    });
+
+    // segment each poly to be tested
+    let thin_test = test_flats.map(poly => {
         return {
             poly,
             points: poly.segment(offset1, true).points
         }
     });
 
-    if (false)
     for (let pi=0, pil=thin_test.length; pi<pil; pi++) {
         for (let pj=pi; pj<pil; pj++) {
             let prec0 = thin_test[pi];
@@ -123,18 +139,19 @@ function offset_default(params) {
             let moved = false;
             for (let i=0; i<pp0.length; i++) {
                 let p0 = pp0[i];
-                if (p0.moved) continue;
+                if (p0.moved !== undefined) continue;
                 for (let j=0; j<pp1.length; j++) {
                     let p1 = pp1[j];
-                    if (p1.moved) continue;
-                    if (p0 === p1 || p0.segment === p1.segment) {
-                        continue;
-                    }
+                    if (p1.moved !== undefined) continue;
+                    if (p0 === p1 || p0.segment === p1.segment) continue;
                     let dist = p0.distTo2D(p1);
                     if (dist < offset1) {
+                        let diff = p0.segment.angle.angleDiff(p1.segment.angle,false);
+                        if (p0.segment === p1.segment && diff < deltaBig) continue;
+                        if (p0.segment !== p1.segment && diff > deltSmall && diff < deltaBig) continue;
                         // merge points marking point offset and skip
                         let mid = p0.midPointTo(p1);
-                        let inc = p0.distTo2D(mid);
+                        let inc = p0.distTo2D(mid) / offset1;
                         moved = p0.moved = p1.moved = inc;
                         p1.skip = true;
                         p0.x = p1.x = mid.x;
@@ -154,36 +171,6 @@ function offset_default(params) {
         }
     }
 
-    // for (let poly of poly.segment(offset1, true)) {
-    //     let ps = poly.segment(offset1, true);
-    //     let pp = ps.points;
-    //     let moved = false;
-    //     pp.push(pp[0]);
-    //     for (let i=0; i<pp.length; i++) {
-    //         let p0 = pp[i];
-    //         if (p0.moved) continue;
-    //         for (let j=i+1; j<pp.length; j++) {
-    //             let p1 = pp[j];
-    //             if (p1.moved) continue;
-    //             if (p0.segment === p1.segment) {
-    //                 continue;
-    //             }
-    //             if (p0.distTo2D(p1) < offset1) {
-    //                 // merge points marking point offset and skip
-    //                 let mid = p0.midPointTo(p1);
-    //                 let inc = p0.distTo2D(mid);
-    //                 moved = p0.moved = p1.moved = inc;
-    //                 p1.skip = true;
-    //                 p0.x = p1.x = mid.x;
-    //                 p0.y = p1.y = mid.y;
-    //             }
-    //         }
-    //     }
-    //     if (moved) {
-    //         poly.points = pp;
-    //     }
-    // }
-
     return { last, gaps };
 }
 
@@ -712,8 +699,12 @@ export function doTopShells(z, top, count, offset1, offsetN, fillOffset, opt = {
                 case "adaptive":
                     ret = thin_type_3({ z, top, count, offsetN });
                     break;
+                case "basic":
                 default:
-                    ret = offset_default({ z, top, count, top_poly, offset1, offsetN, wasm });
+                    ret = offset_default({
+                        z, top, count, top_poly, offset1, offsetN, wasm,
+                        thin: opt.thinType === 'basic'
+                    });
                     break;
             }
             last = ret.last ?? last;