fix split/merge. avoid mirroring cached array

src/main/mesh.js

@@ -295,6 +295,7 @@ function space_init(data) {
                 case 'KeyL':
                     return api.log.toggle();
                 case 'KeyS':
+                    if (shiftKey) return call.edit_split();
                     return selection.visible({toggle:true});
                 case 'KeyB':
                     return selection.boundsBox({toggle:true});

src/mesh/group.js

@@ -152,6 +152,7 @@ mesh.group = class MeshGroup extends mesh.object {
     // ok, this is confusing, but necessary for now :/
     setSelected() {
         super.select();
+        return this;
     }
 };
 

src/mesh/model.js

@@ -143,10 +143,13 @@ mesh.model = class MeshModel extends mesh.object {
             id: this.id,
             opt
         }).then(data => {
-            mesh.api.group.new([new mesh.model({
+            let group = mesh.api.group.new([new mesh.model({
                 file: `${this.file}`,
                 mesh: data
             })]).setSelected();
+            if (opt.mirror) {
+                group.move(0, 0, group.bounds.dim.z);
+            }
         });
     }
 

src/mesh/work.js

@@ -75,13 +75,13 @@ let model = {
         let { id, matrix, opt } = data;
         let array = translate_encode(id, matrix);
         if (opt.mirror) {
+            array = array.slice();
             // find max z and invert z
             let maxz = -Infinity;
             for (let i=2, l=array.length; i<l; i += 3) {
                 maxz = Math.max(maxz, array[i]);
                 array[i] = -array[i];
             }
-            maxz *= 2;
             for (let i=0, l=array.length; i<l; i += 9) {
                 // swap first two vertices in face to invert normals
                 let v1 = array.slice(i, i+3);
@@ -89,7 +89,7 @@ let model = {
                     array[i+j] = array[i+j+3];
                     array[i+j+3] = v1[j];
                 }
-                // move part up in Z
+                // move part up by maxz to compensate for z inversion
                 array[i+2] += maxz;
                 array[i+5] += maxz;
                 array[i+8] += maxz;