Implementing a gradient shader in three.js

Question

I am trying to learn about shaders using three.js. What I am trying to do is create a shader that generates gradients to texture planets with. Right now I am just trying to generate one gradient to make sure it works. However, when I apply the shader it only renders one of the colors, and does not create the gradient effect I'm looking for. I can't seem to find where I'm going wrong with my code.

I'm using the Book of Shaders as the basis for my code. Specifically, I was looking at this example, trying to replicate the background color.

Here is my shader code:

  <section id="fragmentshader">
      #ifdef GL_ES
      precision mediump float;
      #endif

      // #define PI 3.14159265359

      uniform vec2 u_resolution;
      // uniform vec2 u_mouse;
      // uniform float u_time;

      vec3 colorA = vec3(0.500,0.141,0.912);
      vec3 colorB = vec3(1.000,0.833,0.224);



      void main() {
          vec2 st = gl_FragCoord.xy/u_resolution.xy;
          vec3 color = vec3(0.0);

          color = mix( colorA,
                 colorB,
                 st.y);

          gl_FragColor = vec4(color,1.0);
      }
    </section>
    <section id="vertexshader">

      void main() {
        gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
      }
    </section>

and my three.js code inside an a-frame component:

    var uniforms = {
      u_resolution: { type: "v2", value: new THREE.Vector2() },
    };

    var fShader = $('#fragmentshader');
    var vShader = $('#vertexshader');


    var geometry = new THREE.SphereGeometry(getRandomInt(100, 250), 20, 20);

    // var material = new THREE.MeshBasicMaterial( {wireframe: true });
    var material = new THREE.ShaderMaterial({
      uniforms: uniforms,
      vertexShader: vShader.text(),
      fragmentShader: fShader.text()

    });

    var sphere = new THREE.Mesh(geometry, material);

This is what my spheres currently look like

Answer 1

var camera, scene, renderer, mesh, material;
init();
animate();

function init() {
    // Renderer.
    renderer = new THREE.WebGLRenderer();
    //renderer.setPixelRatio(window.devicePixelRatio);
    renderer.setSize(window.innerWidth, window.innerHeight);
    // Add renderer to page
    document.body.appendChild(renderer.domElement);

    // Create camera.
    camera = new THREE.PerspectiveCamera(70, window.innerWidth / window.innerHeight, 1, 1000);
    camera.position.z = 400;

    // Create scene.
    scene = new THREE.Scene();
    
    var uniforms = {
      "color1" : {
        type : "c",
        value : new THREE.Color(0xffffff)
      },
      "color2" : {
        type : "c",
        value : new THREE.Color(0x000000)
      },
    };
    
    var fShader = document.getElementById('fragmentShader').text;
    var vShader = document.getElementById('vertexShader').text;

    // Create material
    var material = new THREE.ShaderMaterial({
      uniforms: uniforms,
      vertexShader: vShader,
      fragmentShader: fShader
    });

    // Create cube and add to scene.
    var geometry = new THREE.BoxGeometry(200, 200, 200);
    mesh = new THREE.Mesh(geometry, material);
    scene.add(mesh);

    // Create ambient light and add to scene.
    var light = new THREE.AmbientLight(0x404040); // soft white light
    scene.add(light);

    // Create directional light and add to scene.
    var directionalLight = new THREE.DirectionalLight(0xffffff);
    directionalLight.position.set(1, 1, 1).normalize();
    scene.add(directionalLight);

    // Add listener for window resize.
    window.addEventListener('resize', onWindowResize, false);

}

function animate() {
    requestAnimationFrame(animate);
    mesh.rotation.x += 0.005;
    mesh.rotation.y += 0.01;
    renderer.render(scene, camera);
}

function onWindowResize() {
    camera.aspect = window.innerWidth / window.innerHeight;
    camera.updateProjectionMatrix();
    renderer.setSize(window.innerWidth, window.innerHeight);
}

<script src="https://rawgit.com/mrdoob/three.js/r86/build/three.min.js"></script>

<script id="vertexShader" type="x-shader/x-vertex">
  varying vec2 vUv;
  void main() {
    vUv = uv;
    gl_Position = projectionMatrix * modelViewMatrix * vec4(position,1.0);
  }
</script>

<script id="fragmentShader" type="x-shader/x-fragment">
  uniform vec3 color1;
  uniform vec3 color2;
  varying vec2 vUv;
  void main() {
    gl_FragColor = vec4(mix(color1, color2, vUv.y),1.0);
  }
</script>