X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pages%2Fblog-0022.html-inc;h=706ea537074945bb91e1162b2494c72640b80ed3;hb=d6a8ee088684c80264483be3fe6c8d5654d0328b;hp=7f9c593d829b4b3118fe033c07d9644cbe13239e;hpb=e785862422f3e827a242fc244bd57b23443887ce;p=sdlgit%2FSDL-Site.git diff --git a/pages/blog-0022.html-inc b/pages/blog-0022.html-inc index 7f9c593..706ea53 100644 --- a/pages/blog-0022.html-inc +++ b/pages/blog-0022.html-inc @@ -1,25 +1,77 @@

-Eye Candy +SDL RC 2.5 decides to play with PDL

-
-clang
-With each imperfect hit
-a legendary blade forms
-
+PDL provides great number crunching capabilities to Perl and SDL provides game-developer quality real-time bitmapping and sound.
+You can use PDL and SDL together to create real-time,
+responsive animations and simulations.
+In this section we will go through the pleasures and pitfalls of working with both powerhouse libraries. -- David Mertnes


-In prep for the TPM meeting we have been working hard to release a new version of SDL Perl and Alien::SDL. After a lot of feed back from testers (Mike Stok, Stuart Watt, and Chas Owens), we where able to get a working version on 64bit and Mac. The releases will be out tomorrow but here
-is some eye candy to tide you guys over.
+

Creating a SDL Surface piddle


+PDL's core type is a piddle.
+Once a piddle is provided to PDL it can go do a numerous amounts of things.
+Please see the example in 'examples/cookbook/pdl.pl' in github.

+

Creating a simple piddle


+First lets get the right modules.

-This is shooter.pl finally working in MacOSX and 64 bit.
+
  use PDL;
+  use SDL::Rect;
+  use SDL::Video;
+  use SDL::Surface;
+  use SDL::PixelFormat;
+

+Suppose you want a surface of size (200,400) and 32 bit (RGBA).

-

+
my ( $bytes_per_pixel, $width, $height ) = ( 4, 200, 400 );
+

+Define the $width, $height and $bytes_per_pixel. Your $bytes_per_pixel is the number of bits (in this case 32) divided by 8 bits per byte. Therefore for our 32 bpp we have 4 Bpp;

-k23z_ mentioned I should get some more SDL_perl videos out to attract some devs. So here goes.
+
my $piddle  = zeros( byte, $bytes_per_pixel, $width, $height );
+

+Create a normal $piddle with zeros, byte format and the Bpp x width x height dimensions.

-Walking Guy from SDLPerl on Vimeo.
-


-

\ No newline at end of file +
my $pointer = $piddle->get_dataref();
+

+Here is where we get the acutal data the piddle is pointing to. We will have SDL create a new surface from this function.
+
+
my $surface = SDL::Surface->new_from( $pointer, $width, $height, 32,
+        $width * $bytes_per_pixel );
+

+Using the same dimensions we create the surface using SDL::Surface->new_form(). The $width * $Bpp is the scanline (pitch) of the surface in bytes.
+
+
warn "Made surface of $width, $height and ". $surface->format->BytesPerPixel;
+   return ( $piddle, $surface );
+

+Finally make sure that the surface acutally has the correct dimensions we gave.
+
+NOTE: $surface->format->BytesPerPixel must return 1,2,3,4. !!
+
+Now you can blit and use the surface as needed; and do PDL operations as required.
+
+

Operating on the Surface safely


+To make sure SDL is in sync with the data. You must call SDL::Video::lock before doing PDL operations on the piddle.
+
+
SDL::Video::lock_surface($surface);
+ 
+    $piddle ( :, 0 : rand(400), 0 : rand(200) ) .=   pdl( rand(225), rand(225), rand(255), 255 );
+

+After that you can unlock the surface to blit.
+
+
SDL::Video::unlock_surface($surface);
+

+

Errors due to BPP at blitting


+When blitting the new surface check for the return value to see if there has been a problem.
+
+
my $b = SDL::Video::blit_surface(
+        $surface,  SDL::Rect->new( 0, 0, $surface->w, $surface->h ),
+        $app, SDL::Rect->new(  ( $app->w - $surface->w ) / 2, ( $app->h - $surface->h ) / 2, $app->w, $app->h )
+       );
+ 
+    die "Could not blit: " . SDL::get_error() if ( $b == -1 );
+

+If the error message is 'Blit combination not supported' that means that the BPP is incorrect or incosistent with the dimensions. After that a simple update_rect will so your new surface on the screen.
+


+

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