Use WebGL texture as a Three.js Texture map

Question

I have a scene with plane which should use WebGL texture (created using gl.createTexture()) as a map for material. Basically, it doesn't matter how this texture will be used, I just need to find a way to pass it to the ShaderMaterial with certain uniform. WebGL texture updates every frame.

The texture is rendered in context of other canvas element and can be used in that context like this:

var imageLocation = gl.getUniformLocation(program, "u_image");
gl.uniform1i(imageLocation, 0);
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, targetTexture1);

I've already tried this solution. But it seems like THREE.Texture() doesn't grab data from raw WebGL texture.

Answer 1

If you dig through the source this will work as of r103. Of course there's no guarantee it will work in the future but then nothing in three is guaranteed to work in the future.

First make a Texture then call forceTextureInitialization to force Three.js to initialize the texture.

  const forceTextureInitialization = function() {
    const material = new THREE.MeshBasicMaterial();
    const geometry = new THREE.PlaneBufferGeometry();
    const scene = new THREE.Scene();
    scene.add(new THREE.Mesh(geometry, material));
    const camera = new THREE.Camera();

    return function forceTextureInitialization(texture) {
      material.map = texture;
      renderer.render(scene, camera);
    };
  }();

Then replace that Texture's WebGL texture with your own like this

const texProps = renderer.properties.get(someTexture);
texProps.__webglTexture = someGLTexture;

Example:

'use strict';

/* global THREE */

function main() {
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({
    canvas: canvas
  });
  
  const fov = 75;
  const aspect = 2; // the canvas default
  const near = 0.1;
  const far = 5;
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  camera.position.z = 2;

  const scene = new THREE.Scene();

  const boxWidth = 1;
  const boxHeight = 1;
  const boxDepth = 1;
  const geometry = new THREE.BoxGeometry(boxWidth, boxHeight, boxDepth);
  
  const forceTextureInitialization = function() {
    const material = new THREE.MeshBasicMaterial();
    const geometry = new THREE.PlaneBufferGeometry();
    const scene = new THREE.Scene();
    scene.add(new THREE.Mesh(geometry, material));
    const camera = new THREE.Camera();

    return function forceTextureInitialization(texture) {
      material.map = texture;
      renderer.render(scene, camera);
    };
  }();
  
  const cubes = []; // just an array we can use to rotate the cubes

  {
    const gl = renderer.getContext();
    const glTex = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, glTex);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 2, 2, 0,
        gl.RGBA, gl.UNSIGNED_BYTE, new Uint8Array([
          255, 0, 0, 255,
          0, 255, 0, 255,
          0, 0, 255, 255,
          255, 255, 0, 255,
        ]));
    gl.generateMipmap(gl.TEXTURE_2D);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
  
    const texture = new THREE.Texture();
    forceTextureInitialization(texture);
    const texProps = renderer.properties.get(texture);
    texProps.__webglTexture = glTex;
    
    const material = new THREE.MeshBasicMaterial({
      map: texture,
    });
    const cube = new THREE.Mesh(geometry, material);
    scene.add(cube);
    cubes.push(cube); // add to our list of cubes to rotate
  }

  function render(time) {
    time *= 0.001;

    cubes.forEach((cube, ndx) => {
      const speed = .2 + ndx * .1;
      const rot = time * speed;
      cube.rotation.x = rot;
      cube.rotation.y = rot;
    });

    renderer.render(scene, camera);

    requestAnimationFrame(render);
  }

  requestAnimationFrame(render);
}

main();

<canvas id="c"></canvas>
<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/103/three.min.js"></script>

Note of course instead of using your own texture you could grab the one the Texture is already using and then manipulate it with WebGL