#define V_CellsPerMeter 48.0
#define V_CellsPerSqMeter (V_CellsPerMeter * V_CellsPerMeter)

////////////////////////////////////////////////////////////
//~ Constant types

G_DeclConstant(G_RWStructuredBufferRef,   V_ShaderConst_State,                0);
G_DeclConstant(G_StructuredBufferRef,     V_ShaderConst_Params,               1);
G_DeclConstant(G_Texture3DRef,            V_ShaderConst_NoiseTex,             2);

Enum(V_SelectionMode)
{
  V_SelectionMode_None,
  V_SelectionMode_Tile,
};

Struct(V_Xforms)
{
  // World <-> ui
  Xform world_to_ui;
  Xform ui_to_world;

  // Draw <-> ui
  Xform draw_to_ui;
  Xform ui_to_draw;

  // World <-> draw
  Xform world_to_draw;
  Xform draw_to_world;

  // World <-> cell
  Xform world_to_cell;
  Xform cell_to_world;
};

Struct(V_GpuState)
{
  u32 particle_seq;  // Atomic monotonically increasing allocation counter sequence for particle ring buffer
};

Struct(V_GpuParams)
{
  // TODO: Use simulation dt
  f32 dt;

  Vec2 target_size;
  G_Texture2DRef target_ro;
  G_RWTexture2DRef target_rw;
  V_Xforms xf;

  u64 seed;

  V_SelectionMode selection_mode;
  S_TileKind equipped_tile;

  b32 has_mouse_focus;
  b32 has_keyboard_focus;
  Vec2 ui_cursor;
  Vec2 draw_cursor;
  Vec2 world_cursor;
  Rng2 ui_selection;
  Rng2 draw_selection;
  Rng2 world_selection;

  Vec2 camera_pos;
  f32 camera_zoom;

  G_Texture2DRef tiles;
  G_StructuredBufferRef quads;
  G_StructuredBufferRef shape_verts;

  u32 emitters_count;
  G_StructuredBufferRef emitters;

  u32 max_particles;
  G_RWStructuredBufferRef particles;

  b32 should_clear_stains;
  G_RWTexture2DRef cells;
  G_RWTexture2DRef stains;
};

////////////////////////////////////////////////////////////
//~ Particle types

Enum(V_ParticleFlag)
{
  V_ParticleFlag_None = 0,
  V_ParticleFlag_StainOnPrune = (1 << 0),
};

Struct(V_Emitter)
{
  V_ParticleFlag flags;

  Vec2 pos;
  u32 count;
  u64 seed;

  f32 speed;
  f32 speed_spread;

  f32 angle;
  f32 angle_spread;

  f32 velocity_falloff;
  f32 velocity_falloff_spread;

  Vec4 color_lin;
  Vec3 color_spread;
};

// TODO: Pack this efficiently
Struct(V_Particle)
{
  V_ParticleFlag flags;

  u32 emitter_init_num;  // if != 0, then initialize using emitter at index (emitter_init_num - 1)
  u32 seq;
  u32 idx_in_emitter;

  Vec2 pos;
  Vec2 velocity;

  f32 exists;

  f32 velocity_falloff;
  Vec3 color;
};

#if IsLanguageC
  Struct(V_EmitterNode)
  {
    V_EmitterNode *next;
    V_Emitter emitter;
  };
#endif

////////////////////////////////////////////////////////////
//~ Quad types

Enum(V_DQuadFlag)
{
  V_DQuadFlag_None            = 0,
};

Struct(V_DQuad)
{
  V_DQuadFlag flags;
};

////////////////////////////////////////////////////////////
//~ Vert types

Struct(V_DVert)
{
  Vec2 pos;
  Vec4 color_lin;
};


////////////////////////////////////////////////////////////
//~ Helpers

#define V_ThreadGroupSizeFromBufferSize(buffer_size) VEC3I32((((buffer_size) + 63) / 64), 1, 1)
#define V_ThreadGroupSizeFromTexSize(tex_size) VEC3I32(((tex_size).x + 7) / 8, ((tex_size).y + 7) / 8, 1)