start passing back thin wall data to slice

src/kiri/core/slice.js

@@ -144,7 +144,8 @@ class Slice {
         } else {
             // create top object from object bundle passed back by slicePost()
             let top = new Top(data.poly);
-            top.thin_fill = data.thin_fill ? data.thin_fill.map(p => newPoint(p.x,p.y,p.z)) : undefined;
+            top.thin_fill = data.thin_fill?.map(p => newPoint(p.x,p.y,p.z));
+            top.thin_wall = data.thin_wall;
             top.fill_lines = data.fill_lines;
             top.fill_sparse = data.fill_sparse;
             top.fill_off = data.fill_off;

src/kiri/mode/fdm/post.js

@@ -170,15 +170,14 @@ function thin_type_3(params) {
     let noodleWidth = offsetN * count;
     let { noodle, remain } = top.poly.noodle(noodleWidth);
 
-    // remaining area for infill after shells are extruded
-    let gaps = top.gaps = remain;
-
     // render inset "noodle"
     // shells.appendAll(noodle);
 
-    let thin = top.thin_fill = [];
-    let shells = top.shells;
-    let sparse = top.fill_sparse = [];
+    let debugRemain = false;
+    let debugExtrusion = false;
+
+    let shells = top.shells; // only used for debug
+    let trace = top.thin_wall = [];
 
     let midR = offsetN * 0.5;  // nominal extrusion width
     let minR = midR * 0.75; // smallest interior fill or single wall width
@@ -187,7 +186,6 @@ function thin_type_3(params) {
 
     let lines = [];
     let polys = [];
-    let trace = [];
 
     for (let i=0; i<count; i++) {
         let remain = [];
@@ -211,7 +209,7 @@ function thin_type_3(params) {
         });
 
         // show remaining noodle after single trace
-        // shells.push(...POLY.setZ(POLY.flatten(remain), z));
+        if (debugRemain) polys.push(...POLY.setZ(POLY.flatten(remain), z));
 
         noodle = remain;
     }
@@ -219,15 +217,17 @@ function thin_type_3(params) {
     // console.log({ lines, polys, trace });
 
     // show extrusion
+    if (debugExtrusion)
     for (let point of trace) {
-        shells.push(newPolygon().centerCircle(point, point.r, 12).setZ(z));
+        polys.push(newPolygon().centerCircle(point, point.r, 12).setZ(z));
     }
 
     POLY.setZ([...lines, ...polys], z);
-    thin.push(...lines);
-    shells.push(...polys);
 
-    return { trace, gaps };
+    if (lines.length) top.thin_fill = lines;
+    if (polys.length) shells.push(...polys);
+
+    return { trace, last: remain };
 }
 
 // trace a single extrusion line around the inside of the noodle poly
@@ -577,8 +577,8 @@ export function doTopShells(z, top, count, offset1, offsetN, fillOffset, opt = {
                     ret = offset_default({ z, top, count, top_poly, offset1, offsetN, wasm });
                     break;
             }
-            last = ret.last || last;
-            gaps = ret.gaps || gaps;
+            last = ret.last ?? last;
+            gaps = ret.gaps ?? gaps;
         }
     } else {
         // no shells, just infill, is permitted

src/kiri/mode/fdm/slice.js

@@ -1001,27 +1001,31 @@ function doRender(slice, isSynth, params, opt = {}) {
             .setLayer(isSynth ? "support" : "shells", isSynth ? Color.support : Color.shell)
             .addPolys(top.shells || [], vopt({ offset, height, clean: true }));
 
-        output
+        if (top.fill_lines?.length) output
             .setLayer("solid fill", isSynth ? Color.support : Color.fill)
             .addLines(top.fill_lines || [], vopt({ offset: offset * solidWidth, height, z:slice.z }));
 
-        if (!(slice.belt && slice.belt.anchor)) output
+        if (!(slice.belt?.anchor)) output
             .setLayer("sparse fill", Color.infill)
             .addPolys(top.fill_sparse || [], vopt({ offset, height, outline: true, trace:true }))
 
-        if (slice.belt && slice.belt.anchor) output
+        if (slice.belt?.anchor) output
             .setLayer("anchor", Color.anchor)
             .addPolys(top.fill_sparse || [], vopt({ offset, height, outline: true, trace:true }))
 
-        if (top.thin_fill) output
+        if (top.thin_fill?.length) output
             .setLayer("thin fill", Color.thin)
             .addLines(top.thin_fill, vopt({ offset, height }));
 
-        if (top.gaps && devel) output
+        if (top.thin_wall?.length) output
+            .setLayer("shells", Color.thin)
+            .addPolys(top.thin_wall.map(p => newPolygon().centerCircle(p, p.r, 12).setZ(slice.z)), vopt({ offset, height }));
+
+        if (top.gaps?.length && devel) output
             .setLayer("gaps", Color.gaps)
             .addPolys(top.gaps, vopt({ offset, height, thin: true }));
 
-        if (isThin && devel && top.fill_off && top.fill_off.length) {
+        if (isThin && devel && top.fill_off?.length) {
             slice.output()
                 .setLayer('fill inset', Color.inset)
                 .addPolys(top.fill_off);