Arranging array positions in ThreeJS

Question

Arranging array positions in ThreeJS

My BufferGeometry contains an array of x/y/z positions with almost 60,000 points (18,000 values),

[3, 2, 1, 3, 2, 1, 3, 2, 1, ...]

To obtain random points, I am considering shuffling these positions and then selecting the first 30,000. One idea is to first convert this array into an array of Vector 3 to retain the trio values.

    [new THREE.Vector3(3, 2, 1), new THREE.Vector3(3, 2, 1), new THREE.Vector3(3, 2, 1), ...]

I could use some help with terminology. Are there specific names for these two arrays? This information will assist me in tackling subsequent questions.

Are there established methods for converting one array into another?

Furthermore, what is the most efficient way to shuffle the original positions array?

javascript arrays sorting three.js

Answer 1

Answer №1

In summary: No conversion to THREE.Vector3 is necessary to extract n random points from the array. There are no specific names assigned to the arrays.

Below, you will find the functions needed to carry out the requested operations:

Is there an optimal method to shuffle the raw positions array? (Yes, details below)

var points = [5, 6, 7, 3, 2, 1, 5, 6, 7, 3, 2, 1, 5, 6, 7]

// Assuming more points exist than required for extraction
function getRandomPoints (points, numberOfPoints) {
  var resultPoints = []
  for (var i = 0; i < numberOfPoints; i++) {
    // Generate a random index
    var randomIndex = Math.floor(Math.random() * points.length);
    var index = (randomIndex - randomIndex % 3)
    resultPoints.push(points[index])
    resultPoints.push(points[index + 1])
    resultPoints.push(points[index + 2])
    points.splice(index, index + 3);
  }

  return resultPoints;
}

var randomPoints = getRandomPoints(points, 2);

Are there specific techniques for converting one array to another? (Yes, explained below)

var points = [5, 6, 7, 3, 2, 1, 5, 6, 7, 3, 2, 1, 5, 6, 7]

function convertToVector (points) {
  var resultPoints = []
  for (var i = 0; i < points.length; i = i + 3) {
    var vectorPoint = new THREE.Vector3(points[i], points[i + 1], points[i + 2])
    resultPoints.push(vectorPoint)
  }
  return resultPoints
}

var convertedPoints = convertToVector(points)

Answer 2

In summary: No conversion to THREE.Vector3 is necessary to extract n random points from the array. There are no specific names assigned to the arrays.

Below, you will find the functions needed to carry out the requested operations:

Is there an optimal method to shuffle the raw positions array? (Yes, details below)

var points = [5, 6, 7, 3, 2, 1, 5, 6, 7, 3, 2, 1, 5, 6, 7]

// Assuming more points exist than required for extraction
function getRandomPoints (points, numberOfPoints) {
  var resultPoints = []
  for (var i = 0; i < numberOfPoints; i++) {
    // Generate a random index
    var randomIndex = Math.floor(Math.random() * points.length);
    var index = (randomIndex - randomIndex % 3)
    resultPoints.push(points[index])
    resultPoints.push(points[index + 1])
    resultPoints.push(points[index + 2])
    points.splice(index, index + 3);
  }

  return resultPoints;
}

var randomPoints = getRandomPoints(points, 2);

Are there specific techniques for converting one array to another? (Yes, explained below)

var points = [5, 6, 7, 3, 2, 1, 5, 6, 7, 3, 2, 1, 5, 6, 7]

function convertToVector (points) {
  var resultPoints = []
  for (var i = 0; i < points.length; i = i + 3) {
    var vectorPoint = new THREE.Vector3(points[i], points[i + 1], points[i + 2])
    resultPoints.push(vectorPoint)
  }
  return resultPoints
}

var convertedPoints = convertToVector(points)

Arranging array positions in ThreeJS

Answer №1

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