How to use GLSL with JEDI-SDL?

[cragwolf]

Does anyone know of an FPC or Delphi demo that shows how to use the OpenGL shading language with JEDI-SDL? Do I need the latest OpenGL headers? Are the ones that come with FPC or JEDI-SDL good enough?

[vgo]

The headers that come with FPC/Lazarus are for OpenGL 1.1, so they are definitely too old.
The headers from JEDI-SDL seem to be outdated too, I'm using the dglOpenGL (http://www.delphigl.com) headers, they should compile on Linux too, but I haven't tried it yet. At least I can compile my test project using the headers with FPC and it runs.

[technomage]

The headers in the JEDI-SDL cvs are up to date and support OpenGL 2.0. These are being tested (by me). I have got a basic framework for GLSL I'll try and post it but you will need the headers from cvs for it to work.

[cragwolf]

Thanks, I'd much appreciate that framework.

[grudzio]

There is a tutorial at http://wiki.delphigl.com/index.php/Tutorial#Shader, but it is in german.

[cragwolf]

Danke sch??n!

[vgo]

I'm having trouble with the shaders... The shader loads just fine and I can set the uniform parameters, but I get "invalid operation" on glEnd();

Here's the vertex program:

void main(void)
{
	gl_TexCoord[0] = gl_MultiTexCoord0;
   gl_Position = ftransform();
}

Fragment program:

uniform sampler2D colorMap;

void main(void)
{
	gl_FragColor = texture2D( colorMap, gl_TexCoord[0].st); 
}

Here's the test code:
[pascal]
glActiveTextureARB(GL_TEXTURE0_ARB);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, Textures[0]);
glCheckForError();
Shader.Enable;
glCheckForError();
Shader.SetParameter('colorMap', GL_TEXTURE0_ARB);
glCheckForError();

glBegin(GL_QUADS);
glColor3f(1, 1, 1);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1, 0);
glVertex3f(10, -10, -30);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1, 1);
glVertex3f(10, 10, -30);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0, 1);
glVertex3f(-10, 10, -30);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0, 0);
glVertex3f(-10, -10, -30);
glEnd();
glCheckForError(); // Error here

Shader.Disable;
[/pascal]

The shader class is just a simple wrapper for loading the programs and setting parameters that I made for testing.

[pascal]
unit uShader;
{
Project Miniverse
http://www.projectminiverse.com

Description:
GLSL shader object

Classes:
TShader

Created:
22.04.2006 (JA)

Modified:

}

interface

uses
{$IFDEF USE_SDL}
GL, GLU, GLEXT,
{$ELSE}
dglOpenGL,
{$ENDIF}
glShader, glGeometry;

type
TShader = class(TObject)
protected
FProgramObject: GLHandleARB;
FName: String;
FResult: String;
public
constructor Create(FileName: String); overload;
constructor Create(const Name, VertexProgram, FragmentProgram: String); overload;
destructor Destroy; override;

procedure Enable;
procedure Disable;
procedure SetParameter(const Name: String; Value: TInt); overload;
procedure SetParameter(const Name: String; Value: TFloat); overload;
procedure SetParameter(const Name: String; Value1, Value2, Value3, Value4: TFloat); overload;

property Name: String read FName;
property ProgramObject: GLHandleARB read FProgramObject;
property Result: String read FResult;
end;

implementation

uses
glUtils;

constructor TShader.Create(FileName: String);
begin
inherited Create;
end;

constructor TShader.Create(const Name, VertexProgram, FragmentProgram: String);
begin
inherited Create;
FName := Name;
FProgramObject := glShader.LoadFragmentandVertexShader(FragmentProgr am, VertexProgram);
FResult := glShader.CheckForErrors(FProgramObject);
glCheckForError();
end;

destructor TShader.Destroy;
begin
inherited Destroy;
end;

procedure TShader.Enable;
begin
glUseProgramObjectARB(FProgramObject);
end;

procedure TShader.Disable;
begin
glUseProgramObjectARB(0);
end;

procedure TShader.SetParameter(const Name: String; Value: TInt);
var
p: PGLcharARB;
l: TInt;
begin
p := PGLCharArb(Name);
glUniform1iARB(glGetUniformLocationARB(FProgramObj ect, p), Value);
end;

procedure TShader.SetParameter(const Name: String; Value: TFloat);
var
p: PGLcharARB;
l: TInt;
begin
p := PGLCharARB(Name);
glUniform1fARB(glGetUniformLocationARB(FProgramObj ect, p), Value);
end;

procedure TShader.SetParameter(const Name: String; Value1, Value2, Value3, Value4: TFloat);
var
p: PGLcharARB;
l: TInt;
begin
p := PGLCharARB(Name);
glUniform4fARB(glGetUniformLocationARB(FProgramObj ect, p), Value1, Value2, Value3, Value4);
end;

end.
[/pascal]

I tried to search for possible reason, but I can't seem to find any.

[technomage]

Doesn't look like a problem with the Shader Programs. I tested the code in the ShaderDesigner and it works. I would first try to get the copde working without a shader (just use the fixed functionality) then add the shader once that is working. There might be a problem in the setup/initialization of the app which is causing the error.

[vgo]

It works if I use ARB multitexturing, but as soon as I try to use the shader I get the error.

I load the ARB extensions for multitexturing and shaders, ie. GL_ARB_multitexture and GL_ARB_shader_objects, do I need something else too? Do I need to initialize the OpenGL pipeline for shaders before using them? Doesn't seem likely as I can load and compile the shaders and the driver says: "Link successful. The GLSL vertex shader will run in hardware. The GLSL fragment shader will run in hardware."

Here's my OpenGL initialization code:
[pascal]
glClearColor(0.0, 0.0, 0.0, 0.0);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
glCullFace(GL_BACK);
glFrontFace(GL_CCW);
glShadeModel(GL_SMOOTH);
glMatrixMode(GL_MODELVIEW);
glEnable(GL_TEXTURE_2D);
[/pascal]

Didn't find any documentation to explain what can I do and what I cannot do when using shaders...

[technomage]

I'll have a look at something similar here and see if I can get it working.