unit Shaders;

interface
uses OpenGL, Classes, SysUtils, Dialogs, OGLExt;

type
TShaderObject = class
 public
   Constructor Create(VSFileName,FSFileName:string);
   Procedure   SetShader; virtual;
   Procedure   ResetShader;
 protected
   VS, FS, SP: integer;
   UseVS, UseFS:boolean;
 end;

implementation
{ TShaderObject }

function LoadShader(const src: String; const stype: GLenum): GLhandleARB;
var
 source: PChar;
 compiled, len: Integer;
 log: String;

function GetInfoLog(s: GLhandleARB): String;
var
 blen, slen: Integer;
 infolog: array of Char;
begin
 glGetObjectParameterivARB(s, GL_OBJECT_INFO_LOG_LENGTH_ARB, @blen);

 if blen > 1 then
 begin
   SetLength(infolog, blen);
   glGetInfoLogARB(s, blen, slen, @infolog[0]);
   Result := String(infolog);
   Exit;
 end;

 Result := '';
end;
begin
   source := PChar(src);
   len := Length(src);

   Result := glCreateShaderObjectARB(stype);

   glShaderSourceARB(Result, 1, @source, @len);
   glCompileShaderARB(Result);
   glGetObjectParameterivARB(Result, GL_OBJECT_COMPILE_STATUS_ARB, @compiled);
   log := GetInfoLog(Result);
   if compiled <> 1 then
   begin
     raise Exception.Create(log);
   end;
end;

function LoadShaderFromFile(const filename: String; const stype: GLenum): GLhandleARB;
var
 txt: TStringList;
 F:TTextFile;
begin
   txt := TStringList.Create;
   txt.LoadFromFile(filename);
   try
     Result := LoadShader(txt.Text, stype);
   except on E: Exception do
     raise Exception.Create(filename + ' contains errors!' + #10 + e.Message);
   end;

   txt.Free;
end;

constructor TShaderObject.Create(VSFileName, FSFileName: string);
begin
 if CanUseShaders then
 begin
   if Length(VSFileName)>0 then if FileExists(VSFileName) then UseVS:=True else UseVS:=False;
   if Length(FSFileName)>0 then if FileExists(FSFileName) then UseFS:=True else UseFS:=False;

   SP:=glCreateProgramObjectARB();

   if UseVS then
   begin
     VS:=LoadShaderFromFile(VSFileName,GL_VERTEX_SHADER_ARB);
     glAttachObjectARB(SP,VS);
   end;

   if UseFS then
     begin
     FS:=LoadShaderFromFile(FSFileName,GL_FRAGMENT_SHADER_ARB);
     glAttachObjectARB(SP,FS);
   end;

   glLinkProgramARB(SP);
 end;
end;

procedure TShaderObject.ResetShader;
begin
 if CanUseShaders then
   glUseProgramObjectARB(0);
end;

procedure TShaderObject.SetShader;
begin
 if CanUseShaders then
   glUseProgramObjectARB(SP);
end;

end.

Constructor Create(VSFileName,FSFileName:string);

Procedure   SetShader;

Procedure   ResetShader;