Galaxies simulation: Change color of a point and display text on mouseover

Question

I am trying to create a simulation of positions of 4673 of the nearest galaxies.

The galaxies are points.

I want to color a point on mouseover and load the name of the galaxy.

I have spent many days trying to achieve it. I am able to change color, as well as do basic raycasting, however, I am unable to separately raycast/color individual point. All the points are raycasted and colored as a group as seen in the current version.

What should I do to correct this? Thank you so much for your time and patience with a beginner.

Complete code is available here.

Relevant code is included below:

window.addEventListener( "mousemove", onDocumentMouseMove, false );

var selectedObject = null;

function onDocumentMouseMove( event ) {

    event.preventDefault();
    if ( selectedObject ) {

        selectedObject.material.color.set( '#fff' );
        selectedObject = null;

    }

    var intersects = getIntersects( event.layerX, event.layerY );
    if ( intersects.length > 0 ) {

        var res = intersects.filter( function ( res ) {

            return res && res.object;

        } )[ 0 ];

        if ( res && res.object ) {

            selectedObject = res.object;
            selectedObject.material.color.set( '#69f' );

        }

    }

}

var raycaster = new THREE.Raycaster();
var mouseVector = new THREE.Vector3();

function getIntersects( x, y ) {

    x = ( x / window.innerWidth ) * 2 - 1;
    y = - ( y / window.innerHeight ) * 2 + 1;

    mouseVector.set( x, y, 0.5 );
    raycaster.setFromCamera( mouseVector, camera );

    return raycaster.intersectObject( dots, true );

}

score 3 · Accepted Answer · answered May 15 '20 at 17:21

First thing to do is to set raycaster.params.Points.threshold equal to the size of your points. This makes it so that the colors of all points change when a user hovers over any point:

(I increased your point size for ease of hovering):

<html>
<head>
  <meta charset="UTF-8">
  <style>
    body { margin: 0; }
  </style>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/110/three.min.js"></script>
  <script src="https://rawcdn.githack.com/mrdoob/three.js/f32e6f14046b5affabe35a0f42f0cad7b5f2470e/examples/js/controls/TrackballControls.js"></script>
</head>

<body>
<script>

// Create an empty scene
var scene = new THREE.Scene();

// Create a basic perspective camera
var camera = new THREE.PerspectiveCamera( 75, window.innerWidth/window.innerHeight, 0.1, 1000 );
camera.position.x = 200;

// Create a renderer with Antialiasing
var renderer = new THREE.WebGLRenderer({antialias:true});

// Configure renderer clear color
renderer.setClearColor("#000000");

// Configure renderer size
renderer.setSize( window.innerWidth, window.innerHeight );

// Append Renderer to DOM
document.body.appendChild( renderer.domElement );

//Add Milky Way
var dotGeometry = new THREE.Geometry();
dotGeometry.vertices.push(new THREE.Vector3( 0, 0, 0));

var rawFile = new XMLHttpRequest();
rawFile.open("GET", "https://rawcdn.githack.com/RiteshSingh/galaxies/9e6a4e54b37647e5a9a1d6f16c017769533fe258/galaxydata.txt", false);
rawFile.onreadystatechange = function ()
{
 if(rawFile.readyState === 4)
 {
  if(rawFile.status === 200 || rawFile.status == 0)
  {
   var allText = rawFile.responseText;
   var data = allText.split("\n");

   for (var i = 0; i < 4672; i++) {
    var parts = data[i].split("\t");

    var D = parts[0];
    var glon = parts[1]*3.1416/180;
    var glat = parts[2]*3.1416/180;

    var z = D*Math.sin(glat);
    var xy = D*Math.cos(glat);
    var x = xy*Math.cos(glon);
    var y = xy*Math.sin(glon);

    dotGeometry.vertices.push(new THREE.Vector3( x, y, z));
   }
  }
 }
}
rawFile.send(null);

var size = 0.32;
var dotMaterial = new THREE.PointsMaterial( { size: size } );
var dots = new THREE.Points( dotGeometry, dotMaterial );
scene.add( dots );

var controls = new THREE.TrackballControls( camera, renderer.domElement );

// Render Loop
var render = function () {
  requestAnimationFrame( render );
  controls.update();
  // Render the scene
  renderer.render(scene, camera);
};
render();

window.addEventListener( "mousemove", onDocumentMouseMove, false );

var selectedObject = null;

function onDocumentMouseMove( event ) {

 event.preventDefault();
 if ( selectedObject ) {

  selectedObject.material.color.set( '#fff' );
  selectedObject = null;

 }

 var intersects = getIntersects( event.layerX, event.layerY );
 if ( intersects.length > 0 ) {

  var res = intersects.filter( function ( res ) {

   return res && res.object;

  } )[ 0 ];

  if ( res && res.object ) {

   selectedObject = res.object;
   selectedObject.material.color.set( '#69f' );

  }

 }

}

var raycaster = new THREE.Raycaster();
raycaster.params.Points.threshold = size;
var mouseVector = new THREE.Vector3();

function getIntersects( x, y ) {

 x = ( x / window.innerWidth ) * 2 - 1;
 y = - ( y / window.innerHeight ) * 2 + 1;

 mouseVector.set( x, y, 0.5 );
 raycaster.setFromCamera( mouseVector, camera );

 return raycaster.intersectObject( dots, true );

}

</script>
</body>
</html>

Then you just need to make it so that only the hovered point changes color:

<html>
<head>
  <meta charset="UTF-8">
  <style>
    body { margin: 0; }
  </style>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/110/three.min.js"></script>
  <script src="https://rawcdn.githack.com/mrdoob/three.js/f32e6f14046b5affabe35a0f42f0cad7b5f2470e/examples/js/controls/TrackballControls.js"></script></script>
</head>

<body>
<script>

// Create an empty scene
var scene = new THREE.Scene();

// Create a basic perspective camera
var camera = new THREE.PerspectiveCamera( 75, window.innerWidth/window.innerHeight, 0.1, 1000 );
camera.position.x = 200;

// Create a renderer with Antialiasing
var renderer = new THREE.WebGLRenderer({antialias:true});

// Configure renderer clear color
renderer.setClearColor("#000000");

// Configure renderer size
renderer.setSize( window.innerWidth, window.innerHeight );

// Append Renderer to DOM
document.body.appendChild( renderer.domElement );

//Add Milky Way
var dotGeometry = new THREE.Geometry();
dotGeometry.vertices.push();

var colors = [];

var rawFile = new XMLHttpRequest();
rawFile.open("GET", "https://rawcdn.githack.com/RiteshSingh/galaxies/9e6a4e54b37647e5a9a1d6f16c017769533fe258/galaxydata.txt", false);
rawFile.onreadystatechange = function ()
{
 if(rawFile.readyState === 4)
 {
  if(rawFile.status === 200 || rawFile.status == 0)
  {
   var allText = rawFile.responseText;
   var data = allText.split("\n");

   for (var i = 0; i < 4672; i++) {
    var parts = data[i].split("\t");

    var D = parts[0];
    var glon = parts[1]*3.1416/180;
    var glat = parts[2]*3.1416/180;

    var z = D*Math.sin(glat);
    var xy = D*Math.cos(glat);
    var x = xy*Math.cos(glon);
    var y = xy*Math.sin(glon);

    dotGeometry.vertices.push(new THREE.Vector3( x, y, z));

    colors.push(new THREE.Color(0xFF0000));
   }
  }
 }
}
rawFile.send(null);

dotGeometry.colors = colors;

var size = 0.32;
var dotMaterial = new THREE.PointsMaterial({
 size: size,
 vertexColors: THREE.VertexColors,
});
var dots = new THREE.Points( dotGeometry, dotMaterial );
scene.add( dots );

var controls = new THREE.TrackballControls( camera, renderer.domElement );

// Render Loop
var render = function () {
  requestAnimationFrame( render );
  controls.update();
  // Render the scene
  renderer.render(scene, camera);
};
render();

window.addEventListener( "mousemove", onDocumentMouseMove, false );

var selectedObject = null;

function onDocumentMouseMove( event ) {

 event.preventDefault();
 if ( selectedObject ) {

  selectedObject.material.color.set( '#fff' );
  selectedObject = null;

 }

 var intersects = getIntersects( event.layerX, event.layerY );
 if ( intersects.length > 0 ) {
  var idx = intersects[0].index;
  dots.geometry.colors[idx] = new THREE.Color(0xFFFFFF);
  dots.geometry.colorsNeedUpdate = true;
  console.log(idx)
 }
}

var raycaster = new THREE.Raycaster();
raycaster.params.Points.threshold = size;
var mouseVector = new THREE.Vector3();

function getIntersects( x, y ) {

 x = ( x / window.innerWidth ) * 2 - 1;
 y = - ( y / window.innerHeight ) * 2 + 1;

 mouseVector.set( x, y, 0.5 );
 raycaster.setFromCamera( mouseVector, camera );

 return raycaster.intersectObject( dots, true );

}

</script>
</body>
</html>

You'll see the points turn white after the user mouses over them.

I'll leave it as a pedagogical exercise for you to determine how to turn the points back to red after the mouse exits a given point :)

Galaxies simulation: Change color of a point and display text on mouseover

1 Answers1

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