fix(modeling): corrected handling of pitch vs height in extrudeHelical

Author: z3dev

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

@@ -1,16 +1,18 @@
 const { TAU } = require('../../maths/constants')
-const slice = require('./slice')
 const mat4 = require('../../maths/mat4')
-const extrudeFromSlices = require('./extrudeFromSlices')
+
 const geom2 = require('../../geometries/geom2')
 
+const extrudeFromSlices = require('./extrudeFromSlices')
+const slice = require('./slice')
+
 /**
  * Perform a helical extrude of the geometry, using the given options.
  *
  * @param {Object} options - options for extrusion
- * @param {Number} [options.angle=TAU] - angle of the extrusion (RADIANS) positive for right-hand rotation, negative for left-hand
+ * @param {Number} [options.angle=TAU] - angle of the extrusion (RADIANS); positive for right-hand rotation, negative for left-hand
  * @param {Number} [options.startAngle=0] - start angle of the extrusion (RADIANS)
- * @param {Number} [options.pitch=10] - elevation gain for each turn
+ * @param {Number} [options.pitch=10] - elevation gain for each full rotation
  * @param {Number} [options.height] - total height of the helix path. Ignored if pitch is set.
  * @param {Number} [options.endOffset=0] - offset the final radius of the extrusion, allowing for tapered helix, and or spiral
  * @param {Number} [options.segmentsPerRotation=32] - number of segments per full rotation of the extrusion
@@ -20,24 +22,23 @@ const geom2 = require('../../geometries/geom2')
  *
  * @example
  * const myshape = circle({size: 3, center: [10, 0]}) // position for extrusion about Z
- * const mycoil = extrudeHelical({angle: TAU*2, pitch: 10, segmentsPerRotation: 64}, myshape))
+ * const mycoil = extrudeHelical({angle: TAU * 2, pitch: 10, segmentsPerRotation: 64}, myshape))
  */
 const extrudeHelical = (options, geometry) => {
   const defaults = {
     angle: TAU,
     startAngle: 0,
     pitch: 10,
+    height: 0,
     endOffset: 0,
     segmentsPerRotation: 32
   }
-  const { angle, endOffset, segmentsPerRotation, startAngle } = Object.assign({}, defaults, options)
-
-  let pitch
-  // ignore height if pitch is set
-  if (!options.pitch && options.height) {
-    pitch = options.height / (angle / TAU)
-  } else {
-    pitch = options.pitch ? options.pitch : defaults.pitch
+  let { angle, startAngle, pitch, height, endOffset, segmentsPerRotation } = Object.assign({}, defaults, options)
+
+  // calculate pitch from height if available
+  if (height != 0) {
+    // height / number of full rotations
+    pitch = height / (angle / TAU)
   }
 
   // needs at least 3 segments for each revolution
@@ -46,7 +47,7 @@ const extrudeHelical = (options, geometry) => {
   if (segmentsPerRotation < minNumberOfSegments) { throw new Error('The number of segments per rotation needs to be at least 3.') }
 
   const shapeSides = geom2.toSides(geometry)
-  if (shapeSides.length === 0) throw new Error('the given geometry cannot be empty')
+  if (shapeSides.length === 0) throw new Error('The given geometry cannot be empty')
 
   // const pointsWithNegativeX = shapeSides.filter((s) => (s[0][0] < 0))
   const pointsWithPositiveX = shapeSides.filter((s) => (s[0][0] >= 0))
@@ -60,9 +61,11 @@ const extrudeHelical = (options, geometry) => {
 
   const calculatedSegments = Math.round(segmentsPerRotation / TAU * Math.abs(angle))
   const segments = calculatedSegments >= 2 ? calculatedSegments : 2
+
   // define transform matrix variables for performance increase
   const step1 = mat4.create()
-  let matrix
+  const step2 = mat4.create()
+
   const sliceCallback = (progress, index, base) => {
     const zRotation = startAngle + angle / segments * index
     const xOffset = endOffset / segments * index
@@ -84,14 +87,13 @@ const extrudeHelical = (options, geometry) => {
       mat4.fromXRotation(mat4.create(), -TAU / 4 * Math.sign(angle)) // rotate the slice correctly to not create inside-out polygon
     )
 
-    matrix = mat4.create()
     mat4.multiply(
-      matrix,
+      step2,
       // finally rotate around Z axis
       mat4.fromZRotation(mat4.create(), zRotation),
       step1
     )
-    return slice.transform(matrix, base)
+    return slice.transform(step2, base)
   }
 
   return extrudeFromSlices(