#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif

varying vec2 v_TexCoords;
varying vec3 v_Normal;
varying vec3 v_ScreenCoords;
varying vec2 v_ScreenTexCoords;

uniform sampler2D maskTex;
uniform float u_Alpha;
uniform float u_Time;
uniform float lightU;
uniform float lightV;

void main()
{
  //init variables
  vec2 screenUV = v_ScreenCoords.xy/v_ScreenCoords.z*.5+.5;
  float alpha = texture2D( maskTex, v_TexCoords ).r;

  vec3 lightDir = normalize( vec3(-1, 0.015, 0.65) );
  vec3 lightDir2 = normalize( vec3(1, -0.2, 0.1) );

  float rim =
    clamp(dot(v_Normal, lightDir), 0.0, 1.0) * 0.8 + // left
    clamp(dot(v_Normal, lightDir2), 0.0, 1.0); // right

  rim = pow(rim, 3.0);// - pow(rim, 25.0);

  vec2 uvDiff = vec2(lightU, lightV) - screenUV;
  uvDiff.y *= 1.7;  //fix aspect ratio
  uvDiff *= 1.5;  //scale smaller

  float falloff = clamp( 1.-sqrt(uvDiff.x*uvDiff.x+uvDiff.y*uvDiff.y ), 0., 1. ) * alpha * rim * u_Alpha;
  // falloff = alpha * rim * u_Alpha * 0.75;

  gl_FragColor = vec4( falloff );
  // gl_FragColor = vec4( vec3(alpha), 1.0 );
}