orm sampler2D displacementMap;

  void main() {
    // should make this a uniform so it's shared
    float displacementScale = 10.0;
    
    vec3 data = texture2D(displacementMap, v_texcoord).rgb;
    vec3 normal = data * 2. - 1.;
    
    // just hard code lightDir and color
    // to make it easy
    vec3 lightDir = normalize(vec3(1, -3, 2));
    float light = dot(lightDir, normal);
    vec3 color = vec3(0.3, 1, 0.1);
    
    gl_FragColor = vec4(color * (light * 0.5 + 0.5), 1);
  }
  `;

  // compile sh