OpenGL Texture mapping

OpenGL Texture mapping

[Alfredo Macias]

Hi all,
I'm working on an Ada project that renders 3D graphics.
While I'm using openGl with no problems for 3D graphics, I'm trying to
implement texutre mapping.  I'm getting the code for texture mapping from a
working CPP project.  However, I'm having trouble getting the translated
code to compile in Ada.  Here is the code:
--------------------------------------
type Unsigned_Char_Type is new Interfaces.C.Unsigned_Char;
type Pix_Color_Type   is array (1 .. 3) of aliased Unsigned_Char_Type;
type Data_Buffer_Type is array (Positive range <>) of aliased
Pix_Color_Type;

Width : Integer := 256;
Height: Integer := 256;
Data :  Data_Buffer_Type;

------------------------------------
      Gl.GlTexImage2D(
              Gl.Gl_TEXTURE_2D,
              Gl.Glsizei(0),
                Gl.Pixelformatenm'(Gl.Gl_Rgb),
                Gl.Glsizei(Width),
                Gl.Glsizei(Height),
              Gl.Glsizei(0),
                Gl.Pixelformatenm'(Gl.Gl_Rgb),
                Gl.Pixeldatatypeenm'(Gl.Gl_Unsigned_Byte),
                Gl.Glpointer
                      (Gl_Pointer_Conversions.To_Pointer
                             (Data(1)(1)'Address)));
-----------------------------------------------------
This is the nasty message I recevie from the compiler; which tells me close
to nothing.
(A also tried without type casting, but got the same message)

1/2: COMP    graphics.platforms.renderers(body) rsd/adalib

  2498:       Gl.GlTexImage2D(
              ---------------- ...
  2509:                              (Data(1)(1)'Address)));
                                     ----------------------
>>> SEMANTIC: Unresolvable expression <8.3, 8.6:28> <RM83 8.3, 8.7:3>

Any ideas why this code is not compiling?
Any help would be greatly appreciated.

Re: OpenGL Texture mapping

[tmoran]

>Here is the code:
>...
>type Data_Buffer_Type is array (Positive range <>) ...
>Data :  Data_Buffer_Type;
  Surely not.

Re: OpenGL Texture mapping

[Martin Krischik]

Alfredo Macias wrote:

> type Data_Buffer_Type is array (Positive range <>) of aliased
> Data :  Data_Buffer_Type;

An indefinite type without contraint and without initialisation? That does
not work. Read here to find out why:

http://en.wikibooks.org/wiki/Programming:Ada:Subtypes#indefinite_subtype

With Regards

Martin

-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com

Re: OpenGL Texture mapping

[Alfredo Macias]

Sorry for the confusion, I only included what I thought was the most
relevant code, but that is just a part of it.

Data :  Data_Buffer_Type; is actually an incoming parameter to this
procedure where I'm trying to do the texture mapping.
Which means that Data was originally instantiated by the caller and
initialized to values read from a bitmap file, so by the time Data is
received by my texture mapping procedure, Data actually contains 256*256
bytes with the bitmap data.  (I have output its contents as text and
manually verified it for correctness right before my call to
Gl.GlTexImage2D).

So other than that, does anything else look incorrect?
Thank you


"Martin Krischik" <martin@krischik.com> wrote in message
news:1243716.dEx2WVfu6a@linux1.krischik.com...
> Alfredo Macias wrote:
>
> > type Data_Buffer_Type is array (Positive range <>) of aliased
> > Data :  Data_Buffer_Type;
>
> An indefinite type without contraint and without initialisation? That does
> not work. Read here to find out why:
>
> http://en.wikibooks.org/wiki/Programming:Ada:Subtypes#indefinite_subtype
>
> With Regards
>
> Martin
>
> -- 
> mailto://krischik@users.sourceforge.net
> http://www.ada.krischik.com

Re: OpenGL Texture mapping

[Martin Krischik]

Alfredo Macias wrote:

> Sorry for the confusion, I only included what I thought was the most
> relevant code, but that is just a part of it.
> 
> Data :  Data_Buffer_Type; is actually an incoming parameter to this
> procedure where I'm trying to do the texture mapping.
> Which means that Data was originally instantiated by the caller and
> initialized to values read from a bitmap file, so by the time Data is
> received by my texture mapping procedure, Data actually contains 256*256
> bytes with the bitmap data.  (I have output its contents as text and
> manually verified it for correctness right before my call to
> Gl.GlTexImage2D).
> 
> So other than that, does anything else look incorrect?

No! But tell you the truth: before I would post a statement like this to
c.l.a I would break it up - one function call at a time - and store all
intermediate result in temporary variables.

declare:

X0 : .... renames Data(1)(1);
X1 : System.Address := X0'Address; 
X2 : .... := Gl_Pointer_Conversions.To_Pointer (X1)
X3 : .... := Gl.Glpointerￜￜ(X2)

begin
ￜￜￜￜￜￜGl.GlTexImage2D(
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜGl.Gl_TEXTURE_2D,
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜGl.Glsizei(0),
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜGl.Pixelformatenm'(Gl.Gl_Rgb),
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜGl.Glsizei(Width),
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜGl.Glsizei(Height),
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜGl.Glsizei(0),
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜGl.Pixelformatenm'(Gl.Gl_Rgb),
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜￜGl.Pixeldatatypeenm'(Gl.Gl_Unsigned_Byte),
ￜￜￜￜￜￜￜￜￜￜￜￜￜￜ.... => X3);
end

That way you get a more meaningfull errror message. Also better if you ever
need to use the debugger. And no difference in perfomace once the optimizer
found out that each variable is only used once. The GNAT optimizer will
actually tell you that all variables are "constant".

BTW: you should name the parameters when there are more then three - I you
need to read your code in half a year you'll be gratefull for it ;-) .

With Regards

Martin
-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com