1  1  1
1  0  1
0  1  1

#version 130

smooth out vec4 vColor;
smooth out vec3 vNormal;
uniform vec4 Transformations;
uniform mat3 Model;
uniform sampler2D heightmap;
uniform sampler2D NoiseTex;
uniform float BaseLOD;

const float reciprocal_size = 1.0 / 127.0;
const float scale_hmap_4 = 1.0 / 4096.0;
const float scale_noise_2 = 1.0 / 1024.0;

vec4 GetHeight(vec2 Coord, float LOD) {
  vec4 result = texture(heightmap, Coord * scale_hmap_4) * 256.0;
  for (float i = 0.0; i < LOD; ++i) {
    result += (texture(NoiseTex, Coord * scale_noise_2 * exp2(i)) - 0.5) * 8.0 / exp2(i) * min(LOD - i, 1.0);
  } 
  return result;
}

vec3 GetNormal(vec2 Coord, float LOD) {
  vec3 Normal;
  Normal.x = (texture(heightmap, (Coord + vec2(1.0, 0.0)) * scale_hmap_4).r - texture(heightmap, (Coord + vec2(-1.0, 0.0)) * scale_hmap_4).r) * 256.0;
  Normal.z = (texture(heightmap, (Coord + vec2(0.0, 1.0)) * scale_hmap_4).r - texture(heightmap, (Coord + vec2(0.0, -1.0)) * scale_hmap_4).r) * 256.0;
  for (float i = 0.0; i < LOD; ++i) {
    Normal.x += (texture(NoiseTex, (Coord + vec2(1.0, 0.0) * scale_noise_2 * exp2(i))).r - texture(NoiseTex, (Coord + vec2(-1.0, 0.0) * scale_noise_2 * exp2(i))).r)
      * 8.0 / exp2(i) * min(LOD - i, 1.0);
   Normal.z += (texture(NoiseTex, (Coord + vec2(0.0, 1.0) * scale_noise_2 * exp2(i))).r - texture(NoiseTex, (Coord + vec2(0.0, -1.0) * scale_noise_2 * exp2(i))).r)
     * 8.0 / exp2(i) * min(LOD - i, 1.0);
  }
  Normal.y = 1.0;
  return normalize(Normal);
}

void main() { 
  vec3 World = Model * gl_Vertex.xzw;
  vec2 TexCoord = World.xy * 0.5 + 0.5;
  World.xy -= Transformations.xy; 
  World.xy *= Transformations.zw; 
  float LodStep = clamp((1.0 - max(abs(World.x), abs(World.y)) * reciprocal_size) * 4.0, 0.0, 1.0);
  vColor = gl_Color * LodStep;
  vec4 Vert = gl_Vertex;
  float lod = BaseLOD + LodStep;
  Vert.y = GetHeight(TexCoord, lod).r;   
  vNormal = GetNormal(TexCoord, lod);
  gl_Position = gl_ModelViewProjectionMatrix * Vert;
}

Vert.y = texelFetch(heightmap, ivec2(floor(TexCoord)), 0).r * 256.0;

Vert.y = texture(heightmap, TexCoord / 4096.0).r * 256.0;