CSG.js restructuring notes

notes.md

CSG.js notes:

• CAG : any boolean ops converts to CSG and back again !
  • sides are very inneficient data structures : there are duplicates of every points! (end of one side, start of next)
  • CAG’s could retain api by just providing accessors to underlying data structures
• Vertex vs Vector :
  • potentially redundant ? needs more investigating
  • “only” has an extra ‘tag’ field nothing more
• methods that can be easily extracted (barely any ‘this’ references, if at all, etc)
  • overCutInsideCorners
    • used in tests only => good candidate
  • getOutlinePaths
    • used in tests
    • used in examples(user api)
    • used in dxf serializer
    • used in svg serializer
  • toCompactBinary
    • used in tests
    • used in jscad core
  • expandedShell
    • used in tests
    • main function underlying expand()
• dependencies:
  • extruder => _toPlanePolygons
  • _toPlanePolygons => _toCSGWall
  • union => _toCSGWall
  • subtract => _toCSGWall
  • intersect => _toCSGWall
• Shapes:
  • Cylinders:
    • RoundedCylinder has no start & end radius specifiable
    • RoundedCylinder default resolution is different from other cylinders
    • Repeated , complex internal code
    • how is cylinderEliptic any different from a standard cylinder ? => can specify 2D radius
      • should still be merged
    • roundedCylinder has sectorAngle parameter: resolution is NOT adapted to angle size : i.e. small angle seems higher res than high angle
    • SCAD-API: cylinderEliptic is not wrapped

Higher level operations, closer to 'standard cad':
Revolve feature:

• can 'replace' current rotateExtrude (can only do a full 360 extrude)
• can be emulated with solidFromSlices: (because it can 'close' shapes) ex

function revolve (shape, options = {}) {
  const defaults = {
    revolveAngle: 90,
    resolution: 10
  }
  const {revolveAngle, resolution} = Object.assign({}, defaults, options)

  return shape.solidFromSlices({
    numslices: resolution,
    loop: false,
    callback: function (t, slice) {
      return this.rotate([0, 20, 0], [-1, 0, 0], revolveAngle / (resolution - 1) * slice)
    }
  })
}

Problem: currently it needs 3d polygons (????)

Vector2D and Vector3D... _x,_y,_x attributes to [1,2,3] internal storage

Test functions to prove correctness of CAG; closed, rotation, etc.

Hopefully, this will find bugs in logic, and remove the need for canonicalize()

Decide on common checks for parameters to API functions.

• perform checks, throw exceptions
• perform checks, use defaults
• no checks, continue processing

Possibly, checks are controlled by Debug settings. This would allow designers to get more information about incorrectly passed values.