out vec4 FragColor;

uniform sampler2D uTexMain;
uniform sampler2D uTexWater;
uniform vec2 uInvRes;
uniform float uTime;
uniform vec3 uCam;

in vec3 aNorm;
in vec2 aUv;
in vec3 aCo;

void main()
{
   vec2 ssuv = gl_FragCoord.xy*uInvRes;
   vec4 mapwater = texture( uTexWater, vec2(aUv.x,aUv.y-uTime));

   float undistort = smoothstep(0.1,0.6,distance( uCam, aCo )*0.1);
   vec2 trimedge = smoothstep(0.0,0.2,1.0-abs(ssuv-0.5)*2.0);
   undistort *= trimedge.x * trimedge.y;

   vec2 warpamt = (mapwater.rg-0.5)*0.05*aUv.y*undistort;
   vec4 mapbackbuffer = texture( uTexMain, ssuv + warpamt );

   float opacity = 1.0-smoothstep(0.4,1.0,aUv.y);
   FragColor = vec4( mapbackbuffer.rgb, opacity );
}