Sprite Labels with React-Three-Renderer (MVCE included)

Question

I'm using react-three-renderer (npm, github) for building a scene with three.js.

I'm attempting to use <sprite> and <spriteMaterial> to make a label that always faces the camera, much like in stemkoski's example.

However, I'm having trouble getting the label to display and appropriately setting its coordinates. I have a minimally verifiable complete example at Sprite-Label-Test. Download it, run npm install, and open _dev/public/home.html.

My goal is to see text displayed where I expect it, but as you'll see, it's just blackness. To prove that the sprite is in the view of the camera, I put a box at the same position. To see that uncomment it from the render method and re-gulp.

Here's my file. It has two main components, the componentDidMount method, where the text is created for the sprite, and the render method.

var React = require('react');
var React3 = require('react-three-renderer');
var THREE = require('three');
var ReactDOM = require('react-dom');

class Simple extends React.Component {
  constructor(props, context) {
    super(props, context);

    // construct the position vector here, because if we use 'new' within render,
    // React will think that things have changed when they have not.
    this.cameraPosition = new THREE.Vector3(0, 0, 100);
  }

  componentDidMount() {
    var text = "Hello world";
    var canvas = document.createElement('canvas');
    var context = canvas.getContext('2d');
    var metrics = context.measureText( text );
    var textWidth = metrics.width;

    context.font = "180px arial Bold";
    context.fillStyle = "rgba(255,0,0,1)";
    context.strokeStyle = "rgba(255,0,0,1)";
    context.lineWidth = 4;

    context.fillText( text, 0, 0);

    var texture = new THREE.Texture(canvas)
    texture.needsUpdate = true;

    this.spriteMaterial.map = texture;
    this.spriteMaterial.useScreenCoordinates = false;
  }

  render() {
    const width = window.innerWidth; // canvas width
    const height = window.innerHeight; // canvas height

    var position = new THREE.Vector3(0, 0, 10);
    var scale = new THREE.Vector3(1,1,1);

    return (<React3
      mainCamera="camera" // this points to the perspectiveCamera which has the name set to "camera" below
      width={width}
      height={height}
    >
      <scene>
        <perspectiveCamera
          name="camera"
          fov={75}
          aspect={width / height}
          near={0.1}
          far={1000}

          position={this.cameraPosition}
        />
        <sprite position={position} scale={scale} ref={(sprite) => this.sprite = sprite}>
          <spriteMaterial ref={(spriteMaterial) => this.spriteMaterial = spriteMaterial}></spriteMaterial>
        </sprite>
        {/*<mesh position={position}>
          <boxGeometry
            width={10}
            height={10}
            depth={10}
          />
          <meshBasicMaterial
            color={0x00ff00}
          />
        </mesh>*/}
      </scene>
    </React3>);
  }
}

ReactDOM.render(<Simple/>, document.querySelector('.root-anchor'));

What am I doing wrong? How can I display a sprite text label in the position established with the line var position = new THREE.Vector3(0, 0, 10);? Thanks in advance.

Answer 1

All you've got is one tiny mistake:

Text drawn on <canvas> is anchored at the bottom-left corner. So drawing text at (0,0) won't even be visible. It'll be entirely outside the canvas (shown in white below):

-    context.fillText( text, 0, 0);
+    context.fillText( text, 0, 18);

This is why @df uses fontsize when setting the drawing location on line 147.

---

Also, you're camera wasn't looking at anything. React-Three lets do this as an attribute to your <perspectiveCamera/>.

+          lookAt={this.cameraLook}

---

I opened a pull request against your MVCE repository.