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Creating a Simple Loft

OCCT category icon with a stylized logo representation

A loft operation is a fundamental technique in 3D modeling that allows you to create complex surfaces by defining a series of 2D profiles (cross-sections) in space. The software then generates a smooth transitional surface that connects these profiles. This is incredibly useful for modeling organic shapes, aerodynamic bodies, or any object with a varying cross-section.

In this tutorial, we'll walk through the process of creating a simple lofted shape. We will define three distinct elliptical wires at different positions and then use the loft operation to generate a surface that smoothly interpolates between them. We'll demonstrate how to achieve this using Rete, Blockly, and TypeScript, providing a clear understanding of the underlying logic and its implementation in different environments.

The power of lofting comes from its versatility. You can:

  • Use different shapes: Combine circles, rectangles, polygons, or even more complex custom curves.
  • Vary the number of profiles: More profiles can lead to more detailed and controlled surfaces.
  • Adjust profile orientation and scale: Tilting or resizing profiles can dramatically alter the resulting shape.
  • Create solids: By setting the makeSolid option to true (where applicable), you can create volumetric bodies instead of just surfaces.
  • Nr of wire edges: For loft to work correctly in most situations you must ensure that you loft wires that contain the same amount of edges to form topologically coherent faces.
  • Order of wires matter: If you reverse the order of wires in the list your loft faces will point to different direction.
  • Wire direction matters: If you reverse directions of wires and their edges, your loft faces will point to different direction.
Bitbybit Platform

Simple Loft Operation

rete logoRete
Script Source (rete)
{
  "id": "rete-v2-json",
  "nodes": {
    "b8a58571ebd30b44": {
      "id": "b8a58571ebd30b44",
      "name": "bitbybit.occt.shapes.wire.createEllipseWire",
      "customName": "ellipse wire",
      "async": true,
      "drawable": true,
      "data": {
        "genericNodeData": {
          "hide": true,
          "oneOnOne": false,
          "flatten": 0,
          "forceExecution": false
        },
        "center": [
          0,
          0,
          0
        ],
        "direction": [
          0,
          1,
          0
        ],
        "radiusMinor": 4,
        "radiusMajor": 8
      },
      "inputs": {},
      "position": [
        409.9140625,
        135.00390625
      ]
    },
    "0999348ac27dbe3a": {
      "id": "0999348ac27dbe3a",
      "name": "bitbybit.occt.shapes.wire.createEllipseWire",
      "customName": "ellipse wire",
      "async": true,
      "drawable": true,
      "data": {
        "genericNodeData": {
          "hide": true,
          "oneOnOne": false,
          "flatten": 0,
          "forceExecution": false
        },
        "center": [
          0,
          0,
          0
        ],
        "direction": [
          0,
          1,
          0
        ],
        "radiusMinor": 1,
        "radiusMajor": 4
      },
      "inputs": {
        "center": {
          "connections": [
            {
              "node": "5b0a2e7a36e52bc6",
              "output": "result",
              "data": {}
            }
          ]
        }
      },
      "position": [
        411.21484375,
        550.01953125
      ]
    },
    "5b0a2e7a36e52bc6": {
      "id": "5b0a2e7a36e52bc6",
      "name": "bitbybit.vector.vectorXYZ",
      "customName": "vector xyz",
      "async": false,
      "drawable": true,
      "data": {
        "genericNodeData": {
          "hide": true,
          "oneOnOne": false,
          "flatten": 0,
          "forceExecution": false
        },
        "x": 0,
        "y": 3,
        "z": 0
      },
      "inputs": {},
      "position": [
        -13.58203125,
        587.8515625
      ]
    },
    "58baa94ee15ce87c": {
      "id": "58baa94ee15ce87c",
      "name": "bitbybit.occt.shapes.wire.createEllipseWire",
      "customName": "ellipse wire",
      "async": true,
      "drawable": true,
      "data": {
        "genericNodeData": {
          "hide": true,
          "oneOnOne": false,
          "flatten": 0,
          "forceExecution": false
        },
        "center": [
          0,
          0,
          0
        ],
        "direction": [
          0,
          1,
          0
        ],
        "radiusMinor": 2,
        "radiusMajor": 6
      },
      "inputs": {
        "center": {
          "connections": [
            {
              "node": "31cc8830d0d5b8d6",
              "output": "result",
              "data": {}
            }
          ]
        }
      },
      "position": [
        414.354436433955,
        962.7267506423071
      ]
    },
    "31cc8830d0d5b8d6": {
      "id": "31cc8830d0d5b8d6",
      "name": "bitbybit.vector.vectorXYZ",
      "customName": "vector xyz",
      "async": false,
      "drawable": true,
      "data": {
        "genericNodeData": {
          "hide": true,
          "oneOnOne": false,
          "flatten": 0,
          "forceExecution": false
        },
        "x": 0,
        "y": 7,
        "z": 0
      },
      "inputs": {},
      "position": [
        -18.337436698711855,
        985.1818818123244
      ]
    },
    "aa7b869ef39ad66c": {
      "id": "aa7b869ef39ad66c",
      "name": "bitbybit.occt.operations.loft",
      "customName": "loft",
      "async": true,
      "drawable": true,
      "data": {
        "genericNodeData": {
          "hide": true,
          "oneOnOne": false,
          "flatten": 0,
          "forceExecution": false
        },
        "makeSolid": false
      },
      "inputs": {
        "shapes": {
          "connections": [
            {
              "node": "5f66390fcd956929",
              "output": "list",
              "data": {}
            }
          ]
        }
      },
      "position": [
        1345.6703881224773,
        574.9945464709863
      ]
    },
    "5f66390fcd956929": {
      "id": "5f66390fcd956929",
      "name": "bitbybit.lists.createList",
      "customName": "create list",
      "data": {},
      "inputs": {
        "listElements": {
          "connections": [
            {
              "node": "b8a58571ebd30b44",
              "output": "result",
              "data": {}
            },
            {
              "node": "0999348ac27dbe3a",
              "output": "result",
              "data": {}
            },
            {
              "node": "58baa94ee15ce87c",
              "output": "result",
              "data": {}
            }
          ]
        }
      },
      "position": [
        938.8623690201757,
        627.1782400352727
      ]
    },
    "71104a241cda7a83": {
      "id": "71104a241cda7a83",
      "name": "bitbybit.draw.drawAnyAsync",
      "customName": "draw any async",
      "async": true,
      "drawable": true,
      "data": {
        "genericNodeData": {
          "hide": false,
          "oneOnOne": false,
          "flatten": 0,
          "forceExecution": false
        }
      },
      "inputs": {
        "entity": {
          "connections": [
            {
              "node": "aa7b869ef39ad66c",
              "output": "result",
              "data": {}
            }
          ]
        },
        "options": {
          "connections": [
            {
              "node": "2b01c4bcdaa8b222",
              "output": "result",
              "data": {}
            }
          ]
        }
      },
      "position": [
        1832.5904062824504,
        751.3332776592763
      ]
    },
    "2b01c4bcdaa8b222": {
      "id": "2b01c4bcdaa8b222",
      "name": "bitbybit.draw.optionsOcctShapeSimple",
      "customName": "options occt shape simple",
      "async": false,
      "drawable": false,
      "data": {
        "genericNodeData": {
          "hide": false,
          "oneOnOne": false,
          "flatten": 0,
          "forceExecution": false
        },
        "precision": 0.001,
        "drawFaces": true,
        "faceColour": "#8000ff",
        "drawEdges": true,
        "edgeColour": "#ffffff",
        "edgeWidth": 2
      },
      "inputs": {},
      "position": [
        1348.8560416190364,
        915.1471633350661
      ]
    }
  }
}

With these examples, you've learned the basics of creating a lofted surface from a series of wire profiles.

Experiment with these parameters to explore the wide range of forms you can achieve with the loft operation. Happy modeling!