//
// The graphics engine GXScene
//
unit GXS.CgPostTransformationShader;
(*
   A shader that uses a texture to distort the view by adjusting texture
   coordinates.
   Does not have any practical use, but is fun to play around with.
*)
interface

uses
  System.Classes,
  System.SysUtils,
  
  GXS.Texture,
  GXS.Cadencer,
  GXS.Context,
  GXS.Scene,
  GXS.RenderContextInfo,
  Stage.TextureFormat,

  GXSL.CustomShader,

  Cg.GL,
  Cg.Import,
  GXS.CgShader;

type

  TCGxCustomPostTransformationShader = class(TCGxCustomShader, IgxPostShader)
  private
    FTransformationPower:      Single;
    FTransformationTexture: TgxTexture;
  protected
    procedure DoApply(var rci: TgxRenderContextInfo; Sender: TObject); override;
    // Implementing IPostShader.
    procedure DoUseTempTexture(const TempTexture: TgxTextureHandle; TextureTarget: TglTextureTarget);
    function GetTextureTarget: TglTextureTarget;
  public
    constructor Create(AOwner: TComponent); override;
    property TransformationPower: Single read FTransformationPower write FTransformationPower;
    property TransformationTexture: TgxTexture read FTransformationTexture write FTransformationTexture;
  end;

  TCGxPostTransformationShader = class(TCGxCustomPostTransformationShader)
  published
    property TransformationPower;
    property TransformationTexture;
  end;

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


//----------------------------------------
// TCGxCustomPostTransformationShader
//----------------------------------------

constructor TCGxCustomPostTransformationShader.Create(AOwner: TComponent);
begin
  inherited;
  with VertexProgram.Code do
  begin
    Add(' ');
    Add('void main( ');
    Add('                    float4  iPos  	: POSITION, ');
    Add('                    float2  iTex0	: TEXCOORD0, ');
    Add('                out float4  oPos  	: POSITION, ');
    Add('                out float2  oTex0 	: TEXCOORD0 ');
    Add('         ) ');
    Add('{ ');
    Add('			oPos  = iPos; ');
    Add('			oTex0 = iTex0; ');
    Add('} ');
  end;


  with FragmentProgram.Code do
  begin
    Add('void main( ');
    Add('                    float2 iTex0 	: TEXCOORD0, ');
    Add('                out float4 oCol  	: COLOR, ');
    Add(' ');
    Add('            uniform samplerRECT snapshotTex, ');
    Add('            uniform sampler2D	transformTex, ');
    Add('            uniform float		screenW, ');
    Add('            uniform float		screenH, ');
    Add('            uniform float		transformPower ');
    Add('         ) ');
    Add('{ ');
    Add(' ');
    Add('	/* Read the offset from the transformation texture ');
    Add('		x offset is in the red channel, ');
    Add('		y offset is in the green channel ');
    Add('	*/ ');
    Add('	float2	offset	= 2 * tex2D( transformTex, iTex0 ).rg -1; ');
    Add(' ');
    Add('	/* When using NPOT texture RECT, you need to scale up the texcoords with ');
    Add('		the screenSize	*/ ');
    Add('            iTex0.x    *= screenW; ');
    Add('            iTex0.y    *= screenH; ');
    Add(' ');
    Add('    /* Apply offset		*/ ');
    Add('    		iTex0	+= offset * transformPower; ');
    Add(' ');
    Add('	/* The result is the pixel from the snapshot, with offset	*/ ');
    Add('    		oCol.rgb	= texRECT( snapshotTex, iTex0 ).rgb; ');
    Add('			oCol.a		= 1; ');
    Add('} ');
  end;

  VertexProgram.OnApply := OnApplyVP;
  FragmentProgram.OnApply := OnApplyFP;
  FragmentProgram.OnUnApply := OnUnApplyFP;

  FTransformationPower := 70;
end;

procedure TCGxCustomPostTransformationShader.DoApply(
  var rci: TgxRenderContextInfo; Sender: TObject);
begin
  inherited;
  FragmentProgram.ParamByName('screenW').SetAsScalar(rci.viewPortSize.cx);
  FragmentProgram.ParamByName('screenH').SetAsScalar(rci.viewPortSize.cy);
  FragmentProgram.ParamByName('transformTex').SetAsTexture2D(FTransformationTexture.Handle);
  FragmentProgram.ParamByName('transformTex').EnableTexture;
  FragmentProgram.ParamByName('transformPower').SetAsScalar(FTransformationPower);
end;

procedure TCGxCustomPostTransformationShader.DoUseTempTexture(
  const TempTexture: TgxTextureHandle; TextureTarget: TglTextureTarget);
begin
  FragmentProgram.ParamByName('snapshotTex').SetAsTextureRECT(TempTexture.Handle);
  FragmentProgram.ParamByName('snapshotTex').EnableTexture;
end;

function TCGxCustomPostTransformationShader.GetTextureTarget: TglTextureTarget;
begin
  Result := ttTextureRect;
end;

end.