HelloGL.js

const React = require("react-native");
const GL = require("gl-react-native");

const shaders = GL.Shaders.create({
  helloGL: {
    frag: `
precision highp float;
varying vec2 uv; // This variable vary in all pixel position (normalized from vec2(0.0,0.0) to vec2(1.0,1.0))

void main () { // This function is called FOR EACH PIXEL
  gl_FragColor = vec4(uv.x, uv.y, 0.5, 1.0); // red vary over X, green vary over Y, blue is 50%, alpha is 100%.
}
    `
  }
});

class HelloGL extends React.Component {
  render () {
    const { width, height } = this.props;
    return <GL.View
      shader={shaders.helloGL}
      width={width}
      height={height}
    />;
  }
}

module.exports = HelloGL;