fresnel.frag

varying vec3 vPositionW;
varying vec3 vNormalW;
uniform float u_intensity;

void main() {
  vec3 color = vec3(.58, .74, 1.);
  float fresnelTerm = dot(vPositionW, vNormalW) * (1. - u_intensity/2.);
  fresnelTerm = clamp(1.0 - fresnelTerm, 0., 1.);

  gl_FragColor = vec4( color * fresnelTerm, 1.) * u_intensity;
}

fresnel.vert

varying vec3 vPositionW;
varying vec3 vNormalW;

void main() {
  mat4 LM = modelMatrix;
  LM[2][3] = 0.0;
  LM[3][0] = 0.0;
  LM[3][1] = 0.0;
  LM[3][2] = 0.0;

  vec3 objectNormal = vec3( normal );
  vec4 GN = LM * vec4(objectNormal.xyz, 1.0);

  vPositionW = normalize( cameraPosition - GN.xyz );
  vNormalW = normalize( GN.xyz );

  gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
}