//
// The graphics engine GLScene
//
unit GLS.Particles;

(* Particle systems, based on replication of full-featured scene objects. *)

interface

{$I Stage.Defines.inc}

uses
  Winapi.OpenGL,
  System.Classes,
  System.SysUtils,

  Stage.VectorTypes,
  GLS.Scene,
  GLS.XCollection,
  GLS.PersistentClasses,
  Stage.VectorGeometry,
  Stage.OpenGLTokens,
  GLS.Context,
  GLS.Color,
  GLS.BaseClasses,
  GLS.RenderContextInfo,
  GLS.State;

type
  TGLParticleEvent = procedure(Sender: TObject; particle: TGLBaseSceneObject) of object;

  (* Manager object of a particle system.
     Particles in a TGLParticles system are described as normal scene objects,
     however their children are to be :
    "particle template" : the first object (index=0), this one will be
    duplicated to create new particles, it does not receive progression
    events and is visible at design-time only.
    "live particle" : the other objects (index>0), this ones are rendered
    and receive progression events.
    TGLParticles may also maintain an internal, non-persistent
    ("freezed") set of objects : the allocated objects pool. Why ? Creating
    and freeing objects takes cpu-cycles, especially for the TComponent class,
    and GLScene objects are TComponent. To reduce this load (and at the expense
    of memory space), the particle systems can move "dead" particles to a pool
    instead of freeing them, and will pick in the pool instead of creating
    new objects when new particles are requested. To take advantage of this
    behaviour, you should set the ParticlePoolSize property to a non-null
    value and use the KillParticle function instead of "Free" to kill a particle.
    All direct access to a TGLParticles children should be avoided.
    For high-performance particle systems of basic particles, you should
    look into GLParticleFX instead, TGLParticles being rather focused on
    complex particles. *)
  TGLParticles = class(TGLImmaterialSceneObject)
  private
    FCubeSize: TGLFloat;
    FEdgeColor: TGLColor;
    FVisibleAtRunTime: Boolean;
    particlePool: TList;
    FParticlePoolSize: Integer;
    FOnCreateParticle: TGLParticleEvent;
    FOnActivateParticle: TGLParticleEvent;
    FOnKillParticle: TGLParticleEvent;
    FOnDestroyParticle: TGLParticleEvent;
    FOnBeforeRenderParticles, FOnAfterRenderParticles: TGLDirectRenderEvent;
  protected
    procedure SetCubeSize(const val: TGLFloat);
    procedure SetEdgeColor(const val: TGLColor);
    procedure SetVisibleAtRunTime(const val: Boolean);
    procedure SetParticlePoolSize(val: Integer);
    procedure ClearParticlePool;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    procedure Assign(Source: TPersistent); override;
    procedure BuildList(var ARci: TGLRenderContextInfo); override;
    procedure DoRender(var ARci: TGLRenderContextInfo;
      ARenderSelf, ARenderChildren: Boolean); override;
    procedure DoProgress(const progressTime: TGLProgressTimes); override;
    (* Request creation of a new particle.
     Particle will be either created or retrieved from the particlePool. *)
    function CreateParticle: TGLBaseSceneObject;
    (* Kill given particle.
       If particlePool is not full, particle will be sent to the pool,
       if not, it will be freed. *)
    procedure KillParticle(aParticle: TGLBaseSceneObject);
    // Kill all particles.
    procedure KillParticles;
  published
    property CubeSize: TGLFloat read FCubeSize write SetCubeSize;
    property EdgeColor: TGLColor read FEdgeColor write SetEdgeColor;
    property VisibleAtRunTime: Boolean read FVisibleAtRunTime write SetVisibleAtRunTime default False;
    (* Size of the particle pool (for storing killed particles).
       Default size is zero, meaning the particlePool is disabled. *)
    property ParticlePoolSize: Integer read FParticlePoolSize write SetParticlePoolSize default 0;
    (* Fired a particle has been created as a template duplicate.
       When the event is triggered, the particle has yet been added  to the scene. *)
    property OnCreateParticle: TGLParticleEvent read FOnCreateParticle write FOnCreateParticle;
    (* Fired when a particle will get in the "live" list.
       The particle has just been "Assigned" with the template, may happen after a creation or a pick from the particle pool. *)
    property OnActivateParticle: TGLParticleEvent read FOnActivateParticle write FOnActivateParticle;
    (* Triggered when a particle is killed.
      When the event is fired, the particle is still parented, after this event, the particle will either go
      to the pool or be destroyed if the pool is full. *)
    property OnKillParticle: TGLParticleEvent read FOnKillParticle write FOnKillParticle;
    // Triggered just before destroying a particle. The particle can be in the pool (ie. not parented)
    property OnDestroyParticle: TGLParticleEvent read FOnDestroyParticle write FOnDestroyParticle;
    // Fired before rendering the first of the particles.
    property OnBeforeRenderParticles: TGLDirectRenderEvent read FOnBeforeRenderParticles write FOnBeforeRenderParticles;
    // Fired after rendering the last of the particles.
    property OnAfterRenderParticles: TGLDirectRenderEvent read FOnAfterRenderParticles write FOnAfterRenderParticles;
  end;

// ------------------------------------------------------------------
implementation
// ------------------------------------------------------------------


//----------------- TGLParticles -----------------------------------------------------

 
constructor TGLParticles.Create(AOwner: TComponent);
begin
  inherited;
  ObjectStyle := ObjectStyle + [osDirectDraw, osNoVisibilityCulling];
  FCubeSize := 1;
  FEdgeColor := TGLColor.Create(Self);
  FEdgeColor.Initialize(clrWhite);
  particlePool := TList.Create;
end;

 
destructor TGLParticles.Destroy;
begin
  FEdgeColor.Free;
  ClearParticlePool;
  particlePool.Free;
  inherited;
end;

procedure TGLParticles.Assign(Source: TPersistent);
begin
  if Source is TGLParticles then
  begin
    FCubeSize := TGLParticles(Source).FCubeSize;
    FEdgeColor.Color := TGLParticles(Source).FEdgeColor.Color;
    FVisibleAtRunTime := TGLParticles(Source).FVisibleAtRunTime;
    ClearParticlePool;
    FParticlePoolSize := TGLParticles(Source).FParticlePoolSize;
    FOnCreateParticle := TGLParticles(Source).FOnCreateParticle;
    FOnActivateParticle := TGLParticles(Source).FOnActivateParticle;
    FOnKillParticle := TGLParticles(Source).FOnKillParticle;
    FOnDestroyParticle := TGLParticles(Source).FOnDestroyParticle;
  end;
  inherited Assign(Source);
end;

procedure TGLParticles.ClearParticlePool;
var
  particle: TGLBaseSceneObject;
  i: Integer;
begin
  if Assigned(FOnDestroyParticle) then
  begin
    for i := 0 to particlePool.Count - 1 do
    begin
      particle := TGLBaseSceneObject(particlePool[i]);
      FOnDestroyParticle(Self, particle);
      particle.Free;
    end;
  end
  else
    for i := 0 to particlePool.Count - 1 do
      TGLBaseSceneObject(particlePool[i]).Free;
  particlePool.Clear;
end;


procedure TGLParticles.BuildList(var ARci: TGLRenderContextInfo);
var
  mi, ma: Single;
begin
  ARci.GLStates.Disable(stLighting);
  ARci.GLStates.Enable(stLineStipple);
  ARci.GLStates.Enable(stLineSmooth);
  ARci.GLStates.Enable(stBlend);
  ARci.GLStates.SetBlendFunc(bfSrcAlpha, bfOneMinusSrcAlpha);
  ARci.GLStates.LineWidth := 1;
  ARci.GLStates.LineStippleFactor := 1;
  ARci.GLStates.LineStipplePattern := $AAAA;
  ma := FCubeSize * 0.5;
  mi := -ma;
  with EdgeColor do
    gl.Color3f(Color.X, Color.Y, Color.Z);
  gl.Begin_(GL_LINE_STRIP);
  // front face
  gl.Vertex3f(ma, mi, mi);
  gl.Vertex3f(ma, ma, mi);
  gl.Vertex3f(ma, ma, ma);
  gl.Vertex3f(ma, mi, ma);
  gl.Vertex3f(ma, mi, mi);
  // partial up back fac
  gl.Vertex3f(mi, mi, mi);
  gl.Vertex3f(mi, mi, ma);
  gl.Vertex3f(mi, ma, ma);
  gl.Vertex3f(mi, ma, mi);
  // right side low
  gl.Vertex3f(ma, ma, mi);
  gl.End_;
  gl.Begin_(GL_LINES);
  // right high
  gl.Vertex3f(ma, ma, ma);
  gl.Vertex3f(mi, ma, ma);
  // back low
  gl.Vertex3f(mi, mi, mi);
  gl.Vertex3f(mi, ma, mi);
  // left high
  gl.Vertex3f(ma, mi, ma);
  gl.Vertex3f(mi, mi, ma);
  gl.End_;
end;


procedure TGLParticles.DoRender(var ARci: TGLRenderContextInfo;
  ARenderSelf, ARenderChildren: Boolean);
begin
  if (csDesigning in ComponentState) or (FVisibleAtRunTime) then
    BuildList(ARci);
  if Assigned(FOnBeforeRenderParticles) then
    FOnBeforeRenderParticles(Self, ARci);
  if csDesigning in ComponentState then
  begin
    // design-time, everything is visible for user convenience
    if Count > 0 then
      Self.RenderChildren(0, Count - 1, ARci);
  end
  else
  begin
    // run-time, template is NOT visible
    if Count > 1 then
      Self.RenderChildren(1, Count - 1, ARci);
  end;
  if Assigned(FOnAfterRenderParticles) then
    FOnAfterRenderParticles(Self, ARci);
end;


procedure TGLParticles.DoProgress(const progressTime: TGLProgressTimes);
var
  i: Integer;
begin
  for i := Count - 1 downto 1 do
    Children[i].DoProgress(progressTime);
  Behaviours.DoProgress(progressTime);
  if Assigned(OnProgress) then
    with progressTime do
      OnProgress(Self, deltaTime, newTime);
end;


procedure TGLParticles.SetCubeSize(const val: TGLFloat);
begin
  if val <> FCubeSize then
  begin
    FCubeSize := val;
    StructureChanged;
  end;
end;


procedure TGLParticles.SetEdgeColor(const val: TGLColor);
begin
  if val <> FEdgeColor then
  begin
    FEdgeColor.Assign(val);
    StructureChanged;
  end;
end;


procedure TGLParticles.SetVisibleAtRunTime(const val: Boolean);
begin
  if val <> FVisibleAtRunTime then
  begin
    FVisibleAtRunTime := val;
    StructureChanged;
  end;
end;


procedure TGLParticles.SetParticlePoolSize(val: Integer);
var
  particle: TGLBaseSceneObject;
begin
  if val < 0 then
    val := 0;
  if FParticlePoolSize <> val then
  begin
    FParticlePoolSize := val;
    with particlePool do
      while Count > val do
      begin
        particle := TGLBaseSceneObject(Items[Count - 1]);
        if Assigned(FOnDestroyParticle) then
          FOnDestroyParticle(Self, particle);
        particle.Free;
        Delete(Count - 1);
      end;
  end;
end;


function TGLParticles.CreateParticle: TGLBaseSceneObject;
begin
  if Count > 0 then
  begin
    if particlePool.Count > 0 then
    begin
      Result := TGLBaseSceneObject(particlePool[particlePool.Count - 1]);
      particlePool.Delete(particlePool.Count - 1);
      Result.Assign(Children[0]);
    end
    else
    begin
      Result := TGLSceneObjectClass(Children[0].ClassType).Create(Self);
      Result.Assign(Children[0]);
      if Assigned(FOnCreateParticle) then
        FOnCreateParticle(Self, Result);
    end;
    AddChild(Result);
    if Assigned(FOnActivateParticle) then
      FOnActivateParticle(Self, Result);
  end
  else
    Result := nil;
end;


procedure TGLParticles.KillParticle(aParticle: TGLBaseSceneObject);
begin
  Assert(aParticle.Parent = Self, 'KillParticle : particle is not mine !');
  if Assigned(FOnKillParticle) then
    FOnKillParticle(Self, aParticle);
  if particlePool.Count < FParticlePoolSize then
  begin
    Remove(aParticle, False);
    particlePool.Add(aParticle)
  end
  else
  begin
    if Assigned(FOnDestroyParticle) then
      FOnDestroyParticle(Self, aParticle);
    aParticle.Free;
  end;
end;


procedure TGLParticles.KillParticles;
begin
  while Count > 1 do
    KillParticle(Children[Count - 1]);
end;

// ------------------------------------------------------------------
initialization
// ------------------------------------------------------------------

  RegisterClass(TGLParticles);

end.