Creating a texture in PHP + OpenGL

[Mark L]

I am trying to create a graphics engine using OpenGL and PHP. I am
currently trying to create a completly white texture to test out the
texturing capabilities.

My idea is to create an array 256x256x3 of the value 255 to create a
completely white texture. When I do this in C it works fine but in PHP I
get a array of red, blue, green and black lines texturing the cube.

I have built a webpage detailing this problem:

http://www.marksblogg.com/opengl-php-texturing/

The texture creation happens in the following code. I appolgies that I
didn't clean up the code more prior to this. Any help or ideas would be
greatly appriciated.


$textpoint = null;
$p = "";
$pos = 0;

for( $x = 0; $x < 256; $x ++ )
for( $y = 0; $y < 256; $y ++ )
for( $d = 0; $d < 4; $d ++ )
{
// comes up black:
//$p[ $pos ] = sprintf( "%c", 255 );

// comes up with Red, green, blue, black stripes
//$p[ $pos ] = 0xff;

// comes up with Red, green, blue, black stripes
$p[ $pos ] = 255;
$pos ++;
}

glGenTextures(1 , &$textpoint );
glBindTexture(G L_TEXTURE_2D, $textpoint[ 0 ] );
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_ FILTER,GL_LINEA R);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_ FILTER,GL_LINEA R);

glTexImage2D(GL _TEXTURE_2D, 0, 3,
256, 256,
0, GL_RGB, GL_UNSIGNED_BYT E, $p);

[Bent Stigsen]

Re: Creating a texture in PHP + OpenGL

Mark L wrote:[color=blue]
> I am trying to create a graphics engine using OpenGL and PHP. I am
> currently trying to create a completly white texture to test out the
> texturing capabilities.
>
> My idea is to create an array 256x256x3 of the value 255 to create a
> completely white texture. When I do this in C it works fine but in PHP I
> get a array of red, blue, green and black lines texturing the cube.
>
> I have built a webpage detailing this problem:
> http://www.marksblogg.com/opengl-php-texturing/
>
> The texture creation happens in the following code. I appolgies that I
> didn't clean up the code more prior to this. Any help or ideas would be
> greatly appriciated.[/color]

I cant really figure it out, seems to me that it has something to do
with a difference in php's internal representation of arrays/scalar
values and the way glTexImage2D works. I have tried different
combinations but only the tweaks below worked for me.

If you got the source code for glTexImage2D, it might reveal somehting.

[color=blue]
> $p = "";[/color]

not vital but
$p = range(0, $width*$height* $depth);
would be more correct as an initialization
[color=blue]
> $pos = 0;
>
> for( $x = 0; $x < 256; $x ++ )
> for( $y = 0; $y < 256; $y ++ )
> for( $d = 0; $d < 4; $d ++ )
> {[/color]

switch ($d) { //color layer
case 0://red 0xR------- //Only the highorder nibble had any effect.
$p[$pos] = 0x50000000;
break;
case 1://green 0xG-------
$p[$pos] = 0x70000000;
break;
case 2://blue 0xB-------
$p[$pos] = 0xa0000000;
break;
case 3://alpha? does not seem to have any effect
$p[$pos] = 0x00000000;
break;
}
$pos ++;

[color=blue]
> }
>
> glGenTextures(1 , &$textpoint );
> glBindTexture(G L_TEXTURE_2D, $textpoint[ 0 ] );
> glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_ FILTER,GL_LINEA R);
> glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_ FILTER,GL_LINEA R);
>
> glTexImage2D(GL _TEXTURE_2D, 0, 3,
> 256, 256,
> 0, GL_RGB, GL_UNSIGNED_BYT E, $p);[/color]

glTexImage2D(GL _TEXTURE_2D, 0, 3,
256, 256,
0, GL_RGBA, GL_UNSIGNED_INT , $p);

Changed to match the structure of "$p"


/Bent