{
 "id": "53-path-pattern",
 "name": "Pattern along a path",
 "description": "120x60x5 plate; d6 hole at (100,15) cut through; patterned 7x along a 3-point arc (100,15)-(60,45)-(20,15), evenly over the arc length.",
 "exercises": [
  "path_pattern",
  "extrude_cut"
 ],
 "units": {
  "length": "mm",
  "angle": "deg",
  "area": "mm2",
  "volume": "mm3"
 },
 "conventions": {
  "world": "right-handed; Z up. XY/XZ/YZ are the origin planes.",
  "sketch_frame": "sketch-local 2D coords; world = plane.origin + x*plane.x_dir + y*plane.y_dir (origin in mm). Profile 'loops' list sketch entity ids.",
  "point_refs": "'<id>.start' / '<id>.end' / '<id>.center' reuse (share) that existing sketch point; 'at' is its position when referenced.",
  "extrude_direction": "positive = along sketch plane normal unless stated",
  "selections": "selected faces/edges carry 'point': a world-space point on the face / the edge's parametric midpoint; pick the nearest face/edge to it."
 },
 "parameters": [],
 "features": [
  {
   "op": "sketch",
   "name": "Plate_sketch",
   "plane": {
    "ref": "XY",
    "origin": [
     0.0,
     0.0,
     0.0
    ],
    "x_dir": [
     1.0,
     0.0,
     0.0
    ],
    "y_dir": [
     0.0,
     1.0,
     0.0
    ],
    "normal": [
     0.0,
     0.0,
     1.0
    ]
   },
   "entities": [
    {
     "type": "line",
     "start": {
      "at": [
       0,
       0
      ]
     },
     "end": {
      "at": [
       120,
       0
      ]
     },
     "id": "l1"
    },
    {
     "type": "line",
     "start": {
      "ref": "l1.end",
      "at": [
       120.0,
       0.0
      ]
     },
     "end": {
      "at": [
       120,
       60
      ]
     },
     "id": "l2"
    },
    {
     "type": "line",
     "start": {
      "ref": "l2.end",
      "at": [
       120.0,
       60.0
      ]
     },
     "end": {
      "at": [
       0,
       60
      ]
     },
     "id": "l3"
    },
    {
     "type": "line",
     "start": {
      "ref": "l3.end",
      "at": [
       0.0,
       60.0
      ]
     },
     "end": {
      "ref": "l1.start",
      "at": [
       0.0,
       0.0
      ]
     },
     "id": "l4"
    }
   ],
   "constraints": [],
   "dimensions": []
  },
  {
   "op": "extrude",
   "name": "Plate",
   "operation": "new",
   "profiles": [
    {
     "sketch": "Plate_sketch",
     "loops": [
      {
       "outer": true,
       "curves": [
        "l1",
        "l2",
        "l3",
        "l4"
       ]
      }
     ]
    }
   ],
   "extent": {
    "type": "distance",
    "distance": 5,
    "direction": "positive"
   },
   "result_bodies": [
    "Plate"
   ]
  },
  {
   "op": "sketch",
   "name": "PathSketch",
   "plane": {
    "ref": "XY",
    "origin": [
     0.0,
     0.0,
     0.0
    ],
    "x_dir": [
     1.0,
     0.0,
     0.0
    ],
    "y_dir": [
     0.0,
     1.0,
     0.0
    ],
    "normal": [
     0.0,
     0.0,
     1.0
    ]
   },
   "entities": [
    {
     "type": "arc_three_point",
     "start": {
      "at": [
       100,
       15
      ]
     },
     "mid": [
      60,
      45
     ],
     "end": {
      "at": [
       20,
       15
      ]
     },
     "id": "a1"
    },
    {
     "type": "circle",
     "center": {
      "ref": "a1.start",
      "at": [
       100.0,
       15.0
      ]
     },
     "radius": 3,
     "id": "c1"
    }
   ],
   "constraints": [],
   "dimensions": []
  },
  {
   "op": "extrude",
   "name": "Hole1",
   "operation": "cut",
   "profiles": [
    {
     "sketch": "PathSketch",
     "loops": [
      {
       "outer": true,
       "curves": [
        "c1"
       ]
      }
     ]
    }
   ],
   "extent": {
    "type": "through_all",
    "direction": "positive"
   },
   "result_bodies": [
    "Plate"
   ]
  },
  {
   "op": "path_pattern",
   "name": "PathPattern1",
   "pattern_of": "features",
   "features": [
    "Hole1"
   ],
   "path": {
    "sketch": "PathSketch",
    "curves": [
     "a1"
    ]
   },
   "count": 7,
   "spacing": 17.875031,
   "distance_type": "spacing (arc-length distance between consecutive instances), starting at the hole and running along the arc toward (20,15)",
   "semantics": "instance k = feature translated by path(k*spacing) - path(0); path(0) is the path's start point, so the feature must sit at the path start",
   "orientation": "identical (not rotated along the path)"
  }
 ]
}