Three js ShaderMaterial Gradient

addSkyGradient(scene) {
      // LIGHTS
      const hemiLight = new HemisphereLight(0xffffff, 0xffffff, 0.6)
      hemiLight.color.setHSL(0.6, 1, 0.6)
      hemiLight.groundColor.setHSL(0.095, 1, 0.75)
      hemiLight.position.set(0, 50, 0)
      scene.add(hemiLight)

      // SKYDOME
      const vertexShader = `varying vec3 vWorldPosition;
			void main() {
				vec4 worldPosition = modelMatrix * vec4( position, 1.0 );
				vWorldPosition = worldPosition.xyz;
				gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
			}`
      const fragmentShader = `
      uniform vec3 topColor;
			uniform vec3 bottomColor;
			uniform float offset;
			uniform float exponent;
			varying vec3 vWorldPosition;
			void main() {

				float h = normalize( vWorldPosition + offset ).y;
				gl_FragColor = vec4( mix( bottomColor, topColor, max( pow( max( h , 0.0), exponent ), 0.0 ) ), 1.0 );

			}`
      const uniforms = {
        topColor: { value: new Color(0x0077ff) },
        bottomColor: { value: new Color(0xffffff) },
        offset: { value: 33 },
        exponent: { value: 0.6 }
      }
      uniforms['topColor'].value.copy(hemiLight.color)
      scene.fog.color.copy(uniforms['bottomColor'].value)
      const skyGeo = new SphereGeometry(4000, 32, 15)
      const skyMat = new ShaderMaterial({
        uniforms,
        vertexShader,
        fragmentShader,
        side: BackSide
      })
      const sky = new Mesh(skyGeo, skyMat)
      scene.add(sky)
    }

Apply color gradient to material on mesh - three.js

I have an STL file loaded into my scene with a single colour applied to a phong material I'd like a way of applying two colours to this mesh's material with a gradient effect applied on the Z axis a

https://stackoverflow.com/questions/52614371/apply-color-gradient-to-material-on-mesh-three-js

mrdoob/three.js

JavaScript 3D Library. Contribute to mrdoob/three.js development by creating an account on GitHub.

https://github.com/mrdoob/three.js/blob/master/examples/webgl_lights_hemisphere.html