gl-line-plot

gl-line-plot

A 3D line plot for WebGL

Example

Try it out in your browser

var shell = require("gl-now")({ clearColor: [0,0,0,0] })
var camera = require("game-shell-orbit-camera")(shell)
var createSelect = require("gl-select")
var createAxes = require("gl-axes")
var createSpikes = require("gl-spikes")
var createLines = require("gl-lines")

var mat4 = require("gl-matrix").mat4

//State variables
var  axes, lines, select, spikes

var pickPoint = null

//Set up camera
camera.lookAt(
  [10, 0, 0], 
  [ 0, 0, 0], 
  [ 0, 1, 0])

shell.on("gl-init", function() {
  var gl = shell.gl

  //Create the line plot
  var polyline = []
  for(var i=0; i<100; ++i) {
    var theta = (i / 100.0) * Math.PI
    polyline.push([
        Math.cos(3*theta),
        Math.sin(3*theta),
        (i/50) - 1.0
      ])
  }
  lines = createLines(gl, {
    position: polyline,
    color: [1,0,0]
  })

  //Create axes object
  axes = createAxes(gl, {
    bounds: [[-1,-1,-1],[ 1, 1, 1]]
  })

  //Create selection buffer
  select = createSelect(gl, [shell.height, shell.width])

  //Create axes spikes
  spikes = createSpikes(gl, {bounds: [[-1,-1,-1], [1,1,1]]})
})

function drawPick(cameraParameters) {
  select.shape = [shell.height, shell.width]
  select.begin(shell.mouse[0], shell.mouse[1], 30)
  lines.drawPick(cameraParameters)
  var selected = select.end()
  pickPoint = lines.pick(selected)
}

shell.on("gl-render", function() {
  var gl = shell.gl
  gl.enable(gl.DEPTH_TEST)

  //Compute camera parameters
  var cameraParameters = {
    view: camera.view(),
    projection: mat4.perspective(
        mat4.create(),
        Math.PI/4.0,
        shell.width/shell.height,
        0.1,
        1000.0)
  }

  //Compute user selection
  drawPick(cameraParameters)

  //Draw the axes + lines
  axes.draw(cameraParameters)
  lines.draw(cameraParameters)

  //If a point is picked, draw it
  if(pickPoint) {
    spikes.position = pickPoint.position
    spikes.draw(cameraParameters)
  }
})

Install

npm install gl-line-plot

API

var createLinePlot = require("gl-line-plot")

Constructor

var plot = createLinePlot(gl, options)

Methods

Basic Drawing

plot.draw(camera)

Draws the line plot with the given camera parameters

• camera is an object with the model, view and projection matrices of the plot as properties.

plot.update(options)

Updates the plot. This takes the following parameters:

• options.position An array of position values for the points on the curve
• options.color An array of color values (or a singular color) for the curve
• options.pickId The selection ID for the line plot
• options.lineWidth The width of the line

plot.dispose()

Destroys the plot and releases all associated resources

Picking

plot.drawPick(camera)

Draws the line plot for picking purposes from the given camera

plot.pick(selection)

Returns selection information from the given user selection data.

• selection is the output from gl-select

Returns An object with the following properties:

• arcLength the arc length parameter of the selection
• position the position of the vertex at the selected point

Properties

plot.bounds

Gives the bounds on the line plot in data coordinates.

plot.clipBounds

Sets a clipping bound on the line plot

Credits

(c) 2014 Mikola Lysenko. MIT License