#version 100
precision mediump float;

varying vec2 texcoord;
varying float v_position;
uniform sampler2D u_image0;
uniform sampler2D u_image1;
uniform vec2 fog;

void main() {

  float fogAmount = smoothstep(fog.x, fog.y, v_position);

  gl_FragColor = 
    texture2D(u_image0, texcoord) 
    * texture2D(u_image1, texcoord) 
    * vec4(1.0 - fogAmount, 1.0 - fogAmount, 1.0 - fogAmount, 1.0 - fogAmount);
  if(gl_FragColor.a < 0.0000001)
    discard;
}