fix(modeling): corrected geom2 mirroring transform

packages/modeling/src/geometries/geom2/transform.js

@@ -1,5 +1,7 @@
 const mat4 = require('../../maths/mat4')
 
+const reverse = require('./reverse.js')
+
 /**
  * Transform the given geometry using the given matrix.
  * This is a lazy transform of the sides, as this function only adjusts the transforms.
@@ -14,7 +16,13 @@ const mat4 = require('../../maths/mat4')
  */
 const transform = (matrix, geometry) => {
   const transforms = mat4.multiply(mat4.create(), matrix, geometry.transforms)
-  return Object.assign({}, geometry, { transforms })
+  const transformed = Object.assign({}, geometry, { transforms })
+  // determine if the transform is mirroring in 2D
+  if (matrix[0] * matrix[5] - matrix[4] * matrix[1] < 0) {
+    // reverse the order to preserve the orientation
+    return reverse(transformed)
+  }
+  return transformed
 }
 
 module.exports = transform

packages/modeling/src/geometries/geom2/transform.test.js

@@ -2,7 +2,13 @@ const test = require('ava')
 
 const mat4 = require('../../maths/mat4')
 
-const { transform, fromPoints, toSides } = require('./index')
+const { measureArea } = require('../../measurements/index.js')
+
+const { mirrorX, mirrorY, mirrorZ } = require('../../operations/transforms/index.js')
+
+const { square } = require('../../primitives/index.js')
+
+const { fromPoints, transform, toOutlines, toSides } = require('./index.js')
 
 const { comparePoints, compareVectors } = require('../../../test/helpers/')
 
@@ -51,3 +57,54 @@ test('transform: adjusts the transforms of geom2', (t) => {
   t.true(comparePoints(another.sides[2], expected.sides[2]))
   t.true(compareVectors(another.transforms, expected.transforms))
 })
+
+test('transform: geom2 mirrorX', (t) => {
+  const geometry = square()
+  const transformed = mirrorX(geometry)
+  t.is(measureArea(geometry), 4)
+  // area will be negative unless we reversed the points
+  t.is(measureArea(transformed), 4)
+  const pts = toOutlines(transformed)[0]
+  const exp = [[-1, 1], [-1, -1], [1, -1], [1, 1]]
+  t.true(comparePoints(pts, exp))
+  t.deepEqual(toSides(transformed), [
+    [[1, 1], [-1, 1]],
+    [[-1, 1], [-1, -1]],
+    [[-1, -1], [1, -1]],
+    [[1, -1], [1, 1]]
+  ])
+})
+
+test('transform: geom2 mirrorY', (t) => {
+  const geometry = square()
+  const transformed = mirrorY(geometry)
+  t.is(measureArea(geometry), 4)
+  // area will be negative unless we reversed the points
+  t.is(measureArea(transformed), 4)
+  const pts = toOutlines(transformed)[0]
+  const exp = [[1, -1], [1, 1], [-1, 1], [-1, -1]]
+  t.true(comparePoints(pts, exp))
+  t.deepEqual(toSides(transformed), [
+    [[-1, -1], [1, -1]],
+    [[1, -1], [1, 1]],
+    [[1, 1], [-1, 1]],
+    [[-1, 1], [-1, -1]]
+  ])
+})
+
+test('transform: geom2 mirrorZ', (t) => {
+  const geometry = square()
+  const transformed = mirrorZ(geometry)
+  t.is(measureArea(geometry), 4)
+  // area will be negative unless we DIDN'T reverse the points
+  t.is(measureArea(transformed), 4)
+  const pts = toOutlines(transformed)[0]
+  const exp = [[-1, -1], [1, -1], [1, 1], [-1, 1]]
+  t.true(comparePoints(pts, exp))
+  t.deepEqual(toSides(transformed), [
+    [[-1, 1], [-1, -1]],
+    [[-1, -1], [1, -1]],
+    [[1, -1], [1, 1]],
+    [[1, 1], [-1, 1]]
+  ])
+})

packages/modeling/src/operations/extrusions/extrudeRotate.js

@@ -93,7 +93,7 @@ const extrudeRotate = (options, geometry) => {
         return [point0, point1]
       })
       // recreate the geometry from the (-) capped points
-      geometry = geom2.reverse(geom2.create(shapeSides))
+      geometry = geom2.create(shapeSides)
       geometry = mirrorX(geometry)
     } else if (pointsWithPositiveX.length >= pointsWithNegativeX.length) {
       shapeSides = shapeSides.map((side) => {

packages/modeling/src/operations/transforms/mirror.test.js

@@ -2,6 +2,8 @@ const test = require('ava')
 
 const { comparePoints, comparePolygonsAsPoints } = require('../../../test/helpers')
 
+const { measureArea } = require('../../measurements')
+
 const { geom2, geom3, path2 } = require('../../geometries')
 
 const { mirror, mirrorX, mirrorY, mirrorZ } = require('./index')
@@ -40,25 +42,29 @@ test('mirror: mirroring of geom2 about X/Y produces expected changes to points',
   // mirror about X
   let mirrored = mirror({ normal: [1, 0, 0] }, geometry)
   let obs = geom2.toPoints(mirrored)
-  let exp = [[5, -5], [0, 5], [-10, -5]]
+  let exp = [[0, 5], [5, -5], [-10, -5]]
   t.notThrows(() => geom2.validate(mirrored))
+  t.is(measureArea(mirrored), measureArea(geometry))
   t.true(comparePoints(obs, exp))
 
   mirrored = mirrorX(geometry)
   obs = geom2.toPoints(mirrored)
   t.notThrows(() => geom2.validate(mirrored))
+  t.is(measureArea(mirrored), measureArea(geometry))
   t.true(comparePoints(obs, exp))
 
   // mirror about Y
   mirrored = mirror({ normal: [0, 1, 0] }, geometry)
   obs = geom2.toPoints(mirrored)
-  exp = [[-5, 5], [0, -5], [10, 5]]
+  exp = [[0, -5], [-5, 5], [10, 5]]
   t.notThrows(() => geom2.validate(mirrored))
+  t.is(measureArea(mirrored), measureArea(geometry))
   t.true(comparePoints(obs, exp))
 
   mirrored = mirrorY(geometry)
   obs = geom2.toPoints(mirrored)
   t.notThrows(() => geom2.validate(mirrored))
+  t.is(measureArea(mirrored), measureArea(geometry))
   t.true(comparePoints(obs, exp))
 })
 
@@ -146,7 +152,7 @@ test('mirror: mirroring of multiple objects produces an array of mirrored object
   t.true(comparePoints(obs, exp))
 
   obs = geom2.toPoints(mirrored[2])
-  exp = [[-5, 5], [0, -5], [10, 5]]
+  exp = [[0, -5], [-5, 5], [10, 5]]
   t.notThrows(() => geom2.validate(mirrored[2]))
   t.true(comparePoints(obs, exp))
 })