Shaders

You can defined and use your custom shader by using three-shader-material element. 

<three-shader-material id="custom-shader-1">
  <three-vertex-shader>
    uniform bool edge;
    varying vec3 vNormal;
    void main(void) {
      vec3 pos = position;
      if (edge) {
        pos += normal * 0.04;
      }
      vNormal = normal;
      gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);
    }
  </three-vertex-shader>
  <three-fragment-shader>
    precision mediump float;
    uniform vec3 lightDirection;
    uniform sampler2D texture;
    uniform vec4 edgeColor;
    varying vec3 vNormal;
    void main(void) {
      if (edgeColor.a > 0.0) {
        gl_FragColor = edgeColor;
      }
      else {
        float diffuse = clamp(dot(vNormal, lightDirection), 0.0, 1.0);
        vec4 smpColor = texture2D(texture, vec2(diffuse, 0.0));
        gl_FragColor = smpColor;
      }
    }
  </three-fragment-shader>
  <three-shader-uniforms>
    <three-shader-variable name="uDirLightPos" type="v3" value="new THREE.Vector3()"></three-shader-variable>
    <three-shader-variable name="edgeColor" type="v4" value="new THREE.Vector4(0, 0, 0, 0)"></three-shader-variable>
    <three-shader-variable name="edge" type="i" value="true"></three-shader-variable>
    <three-shader-variable name="lightDirection" type="v3" value="new THREE.Vector3(0.577,0.577,0.577)"></three-shader-variable>
    <three-shader-variable name="texture" type="t" value="THREE.ImageUtils.loadTexture('../images/toon.png')"></three-shader-variable>
  </three-shader-uniforms>
</three-shader-material>

Although this material can be used in a three-mesh element as usual, I recomend you to use a ref attribute in a three-material element in order for readability. The ref attribute refers other three-material element and its material by ID. 

<three-canvas width="200" height="200" antialias="true" clear-color="#000000" default-light="true">
  <three-camera position="0,0,8" look-at="0,0,0" controls="orbit"></three-camera>
  <three-mesh>
    <three-material ref="custom-shader-1"></three-material>
    <three-torus-geometry radius="0.5" tube="0.3"></three-torus-geometry>
  </three-mesh>
</three-canvas>

Toon Shader

uniform bool edge; varying vec3 vNormal; void main(void) { vec3 pos = position; if (edge) { pos += normal * 0.04; } vNormal = normal; gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0); } precision mediump float; uniform vec3 lightDirection; uniform sampler2D texture; uniform vec4 edgeColor; varying vec3 vNormal; void main(void) { if (edgeColor.a > 0.0) { gl_FragColor = edgeColor; } else { float diffuse = clamp(dot(vNormal, lightDirection), 0.0, 1.0); vec4 smpColor = texture2D(texture, vec2(diffuse, 0.0)); gl_FragColor = smpColor; } } uniform bool edge; varying vec3 vNormal; void main(void) { vec3 pos = position; if (edge) { pos += normal * 0.04; } vNormal = normal; gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0); } precision mediump float; uniform vec3 lightDirection; uniform sampler2D texture; uniform vec4 edgeColor; varying vec3 vNormal; void main(void) { if (edgeColor.a > 0.0) { gl_FragColor = edgeColor; } else { float diffuse = clamp(dot(vNormal, lightDirection), 0.0, 1.0); vec4 smpColor = texture2D(texture, vec2(diffuse, 0.0)); gl_FragColor = smpColor; } }