Three.js/WebGL And 2D Canvas -- Passing GetImageData() Array Into Three.DataTexture()

I'm new to WebGL (and 3D graphics in general) and am using three.js. What I want to do is create multiple textures from a 2D canvas, and use them to render multiple meshes, each wi

Solution 1:

Three.js initializes lazily so theoretically you could init your textures by calling renderer.render

"use strict";

var camera;
var scene;
var renderer;
var group;

init();
animate();

function init() {
  renderer = new THREE.WebGLRenderer({canvas: document.querySelector("canvas")});

  camera = new THREE.PerspectiveCamera(70, 1, 1, 1000);
  camera.position.z = 300;
  scene = new THREE.Scene();
  
  group = new THREE.Object3D();
  scene.add(group);

  var geometry = new THREE.BoxGeometry(50, 50, 50);

  var ctx = document.createElement("canvas").getContext("2d");
  ctx.canvas.width = 128;
  ctx.canvas.height = 128;

  for (var y = 0; y < 3; ++y) {
    for (var x = 0; x < 3; ++x) {
      ctx.textAlign = "center";
      ctx.textBaseline = "middle";
      ctx.fillStyle = "rgb(" + (x * 127) + ",192," + (y * 127) + ")"  ;
      ctx.fillRect(0, 0, 128, 128);
      ctx.fillStyle = "white";
      ctx.font = "60px sans-serif";
      ctx.fillText(x + "x" + y, 64, 64);

      var texture = new THREE.Texture(ctx.canvas);
      texture.needsUpdate = true;
      texture.flipY = true;
      var material = new THREE.MeshBasicMaterial({
        map: texture,
      });
      var mesh = new THREE.Mesh(geometry, material);
      group.add(mesh);
      mesh.position.x = (x - 1) * 100;
      mesh.position.y = (y - 1) * 100;
      
      // render to force three to init the texture
      renderer.render(scene, camera);
    }
  }
}

function resize() {
  var width = renderer.domElement.clientWidth;
  var height = renderer.domElement.clientHeight;
  if (renderer.domElement.width !== width || renderer.domElement.height !== height) {
    renderer.setSize(width, height, false);
    camera.aspect = width / height;
    camera.updateProjectionMatrix();
  }
}

function animate() {
  resize();
  group.rotation.x += 0.005;
  group.rotation.y += 0.01;

  renderer.render(scene, camera);
  requestAnimationFrame(animate);
}

body { margin: 0; }
canvas { width: 100vw; height: 100vh; display: block; }

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r79/three.min.js"></script>
<canvas></canvas>

You can also call renderer.setTexture(texture, slot) which works but is arguably the wrong thing to do as based on both the name, docs, and signature of the function there's no guarantee this will work in the future.

"use strict";

var camera;
var scene;
var renderer;
var group;

init();
animate();

function init() {
  renderer = new THREE.WebGLRenderer({canvas: document.querySelector("canvas")});

  camera = new THREE.PerspectiveCamera(70, 1, 1, 1000);
  camera.position.z = 300;
  scene = new THREE.Scene();
  
  group = new THREE.Object3D();
  scene.add(group);

  var geometry = new THREE.BoxGeometry(50, 50, 50);

  var ctx = document.createElement("canvas").getContext("2d");
  ctx.canvas.width = 128;
  ctx.canvas.height = 128;

  for (var y = 0; y < 3; ++y) {
    for (var x = 0; x < 3; ++x) {
      ctx.textAlign = "center";
      ctx.textBaseline = "middle";
      ctx.fillStyle = "rgb(" + (x * 127) + ",192," + (y * 127) + ")"  ;
      ctx.fillRect(0, 0, 128, 128);
      ctx.fillStyle = "white";
      ctx.font = "60px sans-serif";
      ctx.fillText(x + "x" + y, 64, 64);

      var texture = new THREE.Texture(ctx.canvas);
      texture.needsUpdate = true;
      texture.flipY = true;
      var material = new THREE.MeshBasicMaterial({
        map: texture,
      });
      var mesh = new THREE.Mesh(geometry, material);
      group.add(mesh);
      mesh.position.x = (x - 1) * 100;
      mesh.position.y = (y - 1) * 100;
      
      // make three init the texture
      var slot = 0; // doesn't matter what slot as we're not 
      renderer.setTexture(texture, slot);
    }
  }
}

function resize() {
  var width = renderer.domElement.clientWidth;
  var height = renderer.domElement.clientHeight;
  if (renderer.domElement.width !== width || renderer.domElement.height !== height) {
    renderer.setSize(width, height, false);
    camera.aspect = width / height;
    camera.updateProjectionMatrix();
  }
}

function animate() {
  resize();
  group.rotation.x += 0.005;
  group.rotation.y += 0.01;

  renderer.render(scene, camera);
  requestAnimationFrame(animate);
}

body { margin: 0; }
canvas { width: 100vw; height: 100vh; display: block; }

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r79/three.min.js"></script>
<canvas></canvas>

As for flipping use texture.flipY = true;