#extension GL_EXT_texture_array : enable

uniform vec2 mapSize;

uniform sampler2D tileTexture;
uniform sampler2DArray tilesetTexture;

uniform float lod;

void main()
{
   vec2 texCoords = gl_TexCoord[0].st;
   
   //tileResult contains (tileIndex, x, y). Multiply by 65535 to convert the normalized values to shorts.
   vec3 tileResult = texture2D(tileTexture, texCoords / mapSize).rgb * 65535.0; 
   
   //Extract...
   float tile = tileResult.r;
   vec2 tilePosition = tileResult.gb;
   
   gl_FragColor = texture2DArrayLod(tilesetTexture, vec3(texCoords - tilePosition, tile), lod);
}