man SDL::OpenGL () - a perl extension

NAME

SDL::OpenGL - a perl extension

DESCRIPTION

SDL::OpenGL is a perl module which when used by your application exports the gl* and glu* functions into your application's primary namespace. Most of the functions described in the OpenGL 1.3 specification are currently supported in this fashion. As the implementation of the OpenGL bindings that comes with SDL_perl is largely type agnositic, there is no need to decline the function names in the fashion that is done in the C API. For example, glVertex3d is simply glVertex, and perl just does the right thing with regards to types.

CAVEATS

The following methods work different in Perl than in C:

glCallLists
        glCallLists(@array_of_numbers);
Unlike the C function, which get's passed a count, a type and a list of numbers, the Perl equivalent only takes a list of numbers. Note that this is slow, since it needs to allocate memory and construct a list of numbers from the given scalars. For a faster version see glCallListsString.
glReadPixels
        $scalar = glReadPixels($x,$y,$width,$height,$format,$type);
Reads the pixels at CW$x,$y and returnes them packed into the scalar. Here is a short example on how to make a screenshot of an OpenGL app and save it to a BMP file: 
        # get the data from the screen  
        $data = glReadPixels(0,0,$width,$height,GL_GBR,GL_UNSIGNED_BYTE);
        SaveBMP ($filename, $width, $height, 24, $data);
See also glSaveBMP(), which implements this.

The following methods exist in Perl in addition to the normal OpenGL specification:

glCallListsScalar
        glCallListsScalar($string);
Works like glCallLists(), except that it needs only one parameter, a scalar holding a string. The string is interpreted as a set of bytes, and each of these will be passed to glCallLists as GL_BYTE. This is faster than glCallLists, so you might want to pack your data like this: 
        my $lists = pack("C", @array_of_numbers);
And later use it like this: 
        glCallListsScalar($lists);
glReadPixel
        ($r,$g,$b,$a) = glReadPixel($x,$y);
Reads one pixel and unpacks the returned data into RGBA. If you specified a pixel type different than GL_BGRA or GL_RGBA, only partial information is returned, e.g. GL_BLUE sets CW$b, and leaves CW$r,$g and CW$a as 0.
SDL::OpenGL::SaveBMP
        SDL::OpenGL::SaveBMP ($file, $width, $height, $bits_per_pixel, $data);
Save the data in CW$data to a BMP file. CW$data must contain 3-byte per pixel, BGR packed data and CW$bits_per_pixel must (currently) be 24. See glReadPixels() for an example how to get the data.

AUTHOR

David J. Goehrig, additional doc plus SaveBMP by Tels

SEE ALSO

perl, SDL::App and SDL::OpenGL::Constants.