Three.js fragment shader color transition

Question

I'm trying to animate the color transition for ShaderMaterial. I want to have 5 colors, and switch them every few seconds for a whole object (wave of particles).

Here is my JS code

var material = new THREE.ShaderMaterial( {
    uniforms: {
      color: { value: new THREE.Color('violet') },
    },
    vertexShader: document.getElementById( 'vertexshader' ).textContent,
    fragmentShader: document.getElementById( 'fragmentshader' ).textContent
  });

And fragment shader part:

   uniform vec3 color;
   void main() {
      if ( length( gl_PointCoord - vec2( 0.5, 0.5 ) ) > 0.475 ) discard; 
      gl_FragColor = vec4(color, 1.0 );
    }

I have just a little idea of how three.js works. Any suggestions highly appreciated! :)

All code is here: codepen.io/agrhff/pen/MWKEqQy

prisoner849 · Accepted Answer · 2020-07-03 07:36:47Z

As an option, you can use setInterval():

body {
  background-color: black;
  overflow: hidden;
  margin: 0;
}

<script type="x-shader/x-vertex" id="vertexshader">

  attribute float scale;

  void main() {

    vec4 mvPosition = modelViewMatrix * vec4( position, 1.0 );

    gl_PointSize = scale * ( 300.0 / - mvPosition.z );

    gl_Position = projectionMatrix * mvPosition;

  }

</script>

<script type="x-shader/x-fragment" id="fragmentshader">
  uniform vec3 color;
  void main() {


    if ( length( gl_PointCoord - 0.5 ) > 0.475 ) discard;

    gl_FragColor = vec4(color, 1.0 );

  }

</script>
<script type="module">
import * as THREE from 'https://threejs.org/build/three.module.js';

import Stats from 'https://threejs.org/examples/jsm/libs/stats.module.js';

var SEPARATION = 100, AMOUNTX = 150, AMOUNTY = 100;

var container, stats;
var camera, scene, renderer;

var particles, count = 0;

var mouseX = 0, mouseY = -500;

var windowHalfX = window.innerWidth / 2;
var windowHalfY = window.innerHeight / 2;

var colors = [
  new THREE.Color(0xffff00),
  new THREE.Color(0xff00ff),
  new THREE.Color(0x00ffff),
  new THREE.Color(0xffffff),
  new THREE.Color(0x888888)
];
var colIdx = 0;

init();
animate();

function init() {

  container = document.createElement( 'div' );
  container.classList.add("mystyle");
  document.body.appendChild( container );

  camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 1, 10000 );
  camera.position.z = 1000;
  scene = new THREE.Scene();

  //

  var numParticles = AMOUNTX * AMOUNTY;

  var positions = new Float32Array( numParticles * 3 );
  var scales = new Float32Array( numParticles );
  
  var i = 0, j = 0;

  for ( var ix = 0; ix < AMOUNTX; ix ++ ) {

    for ( var iy = 0; iy < AMOUNTY; iy ++ ) {

      positions[ i ] = ix * SEPARATION - ( ( AMOUNTX * SEPARATION ) / 2 ); // x
      positions[ i + 1 ] = 0; // y
      positions[ i + 2 ] = iy * SEPARATION - ( ( AMOUNTY * SEPARATION ) / 2 ); // z

      scales[ j ] = 1;

      i += 3;
      j ++;

    }

  }
  
  var geometry = new THREE.BufferGeometry();
  geometry.setAttribute( 'position', new THREE.BufferAttribute( positions, 3 ) );
  geometry.setAttribute( 'scale', new THREE.BufferAttribute( scales, 1 ) );

  
  var material = new THREE.ShaderMaterial( {
    uniforms: {
      color: { value: new THREE.Color('violet') }
    },
    vertexShader: document.getElementById( 'vertexshader' ).textContent,
    fragmentShader: document.getElementById( 'fragmentshader' ).textContent

  } );

  //

  particles = new THREE.Points( geometry, material);
  scene.add( particles );

  //

  renderer = new THREE.WebGLRenderer( { antialias: true, alpha: true } );
  renderer.setPixelRatio( window.devicePixelRatio );
  renderer.setSize( window.innerWidth, window.innerHeight );
  container.appendChild( renderer.domElement );
  stats = new Stats();
  container.appendChild( stats.dom );

  document.addEventListener( 'mousemove', onDocumentMouseMove, false );
  document.addEventListener( 'touchstart', onDocumentTouchStart, false );
  document.addEventListener( 'touchmove', onDocumentTouchMove, false );

  //

  window.addEventListener( 'resize', onWindowResize, false );
  
  // change the colours, one a second
  setInterval(function(){
    colIdx = (colIdx + 1) % 5;;
    material.uniforms.color.value.copy(colors[colIdx]);
  }, 1000);

}

function onWindowResize() {

  windowHalfX = window.innerWidth / 2;
  windowHalfY = window.innerHeight / 2;

  camera.aspect = window.innerWidth / window.innerHeight;
  camera.updateProjectionMatrix();

  renderer.setSize( window.innerWidth, window.innerHeight );

}

//

function onDocumentMouseMove( event ) {

  mouseX = event.clientX - windowHalfX;
  // mouseY = event.clientY - windowHalfY;

}

function onDocumentTouchStart( event ) {

  if ( event.touches.length === 1 ) {

    event.preventDefault();

    mouseX = event.touches[ 0 ].pageX - windowHalfX;
    // mouseY = event.touches[ 0 ].pageY - windowHalfY;

  }

}

function onDocumentTouchMove( event ) {

  if ( event.touches.length === 1 ) {

    event.preventDefault();

    mouseX = event.touches[ 0 ].pageX - windowHalfX;
    // mouseY = event.touches[ 0 ].pageY - windowHalfY;

  }

}

//

function animate() {

  requestAnimationFrame( animate );

  render();
  stats.update();

}

function render() {

  camera.position.x += ( mouseX - camera.position.x ) * .05;
  camera.position.y += ( - mouseY - camera.position.y );
  camera.lookAt( scene.position );

  var positions = particles.geometry.attributes.position.array;
  var scales = particles.geometry.attributes.scale.array;

  var i = 0, j = 0;

  for ( var ix = 0; ix < AMOUNTX; ix ++ ) {

    for ( var iy = 0; iy < AMOUNTY; iy ++ ) {

      positions[ i + 1 ] = ( Math.sin( ( ix + count ) * 0.3 ) * 50 ) +
        ( Math.sin( ( iy + count ) * 0.5 ) * 50 );

      scales[ j ] = ( Math.sin( ( ix + count ) * 0.3 ) + 1 ) * 8 +
        ( Math.sin( ( iy + count ) * 0.5 ) + 1 ) * 8;

      i += 3;
      j ++;

    }

  }

  particles.geometry.attributes.position.needsUpdate = true;
  particles.geometry.attributes.scale.needsUpdate = true;

  renderer.render( scene, camera );

  count += 0.1;

}
</script>

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