// #include "res://addons/rokojori_action_library/Runtime/Shading/Library/Wind.gdshaderinc"


#include "res://addons/rokojori_action_library/Runtime/Shading/Library/Math.gdshaderinc"
#include "res://addons/rokojori_action_library/Runtime/Shading/Library/Transform.gdshaderinc"


/*
uniform sampler2D terrainHeightMap;
uniform vec2 terrainCenterXZ = vec2( 0.0, 0.0 );
uniform vec2 terrainSizeXZ = vec2( 100.0, 100.0 );
uniform float terrainMinHeight = 0.0;
uniform float terrainMaxHeight = 100.0;

uniform sampler2D terrainNormalMap;
*/

void addTerrainOffset(   
  mat4 _MODEL_MATRIX, 
  inout vec3 _VERTEX, 
  
  sampler2D terrainHeightMap,
  vec2 terrainCenterXZ,
  vec2 terrainSizeXZ,
  float terrainMinHeight,
  float terrainMaxHeight

)
{
  vec3 worldVertex = localToWorld( _VERTEX, _MODEL_MATRIX );

  vec2 mapOffset = terrainCenterXZ - terrainSizeXZ/2.0;

  vec2 uv = ( worldVertex.xz - mapOffset ) / terrainSizeXZ;

  float height = mix( terrainMinHeight, terrainMaxHeight, texture( terrainHeightMap, uv ).r );

  worldVertex.y += height;

  _VERTEX = worldToLocal( worldVertex, _MODEL_MATRIX );

}

/** The world-space normal HeightMapGenerator baked into terrainNormalMap.

    Stored encoded, n * 0.5 + 0.5, so the map also works in an 8-bit format - see
    Procedural/HeightMaps/Shaders/HeightMapNormals.gdshader. World space, not
    tangent space: a heightfield over world XZ has no tangent frame to be
    relative to.

    This replaces taking a central difference per fragment. Besides being
    cheaper, it is the only way the smoothing can exist at all - a consumer
    sampling its own two neighbours has nothing to widen the stencil with, and a
    clipmap's triangles are far coarser than the map, so a vertex normal is not
    an option either.
*/
vec3 getTerrainNormal(
  sampler2D terrainNormalMap,
  vec3 worldPosition,
  vec2 terrainCenterXZ,
  vec2 terrainSizeXZ
)
{
  // An unassigned sampler is Godot's 1x1 default and reads black, and
  // normalize( black * 2 - 1 ) is a diagonal rather than up - so a material
  // whose generator has no normalMapTarget would get wrong lighting instead of
  // flat lighting. A real normal map is never 1x1, so the size is a safe test.
  if ( textureSize( terrainNormalMap, 0 ).x <= 1 )
  {
    return vec3( 0.0, 1.0, 0.0 );
  }

  vec2 mapOffset = terrainCenterXZ - terrainSizeXZ/2.0;

  vec2 uv = ( worldPosition.xz - mapOffset ) / terrainSizeXZ;

  return normalize( texture( terrainNormalMap, uv ).rgb * 2.0 - 1.0 );
}