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12-PDL_OpenGL.pod

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PDL

The Perl Data Language (PDL) is a tool aimed at a more scientifc crowd. Accuracy is paramount and speed is the name of the game. PDL brings to Perl fast matrix and numerical calculations. For games in most cases a accuracy is not critical, but speed and effiency is a great concern. For this reason we will breifly explore how to share SDL texture data between PDL and OpenGL.

+ use strict;
+ use warnings;
+ use SDL;
+ use SDL::Video;
+ use SDLx::App;
+
+ use PDL;
+
+ my $app = SDLx::App->new(
+                           title => 'PDL and SDL application',
+                           width => 640, height => 480, depth => 32,
+                           eoq => 1);

Attaching the Piddle

PDL core object is something called a piddle. To be able to perform PDL calculations and show them on SDL surfaces, we need to share the memory between them. SDL Surface memory is stored in a void * block called pixels. void * memory has the property that allows Surfaces to have varying depth, and pixel formats. This also means that we can have PDL's memory as our pixels for our surface.

+ sub make_surface_piddle {
+ my ( $bytes_per_pixel, $width, $height) = @_;
+ my $piddle = zeros( byte, $bytes_per_pixel, $width, $height );
+ my $pointer = $piddle->get_dataref();

At this point we have a pointer to the $piddle's memory with the given specifications. Next we have our surface use that memory.

+ my $s = SDL::Surface->new_form( 
+                                       $pointer, $width, $height, 32, 
+                                       $width * $bytes_per_pixel 
+                                      );
+
+ #Wrap it into a SDLx::Surface for ease of use
+ my $surface = SDLx::Surface->new( surface => $s );
+
+ return ( $piddle, $surface );
+ }

Lets make some global variables to hold our $piddle and $surface.

+ my ( $piddle, $surface ) = make_surface_piddle( 4, 400, 200 );

Drawing and Updating

make_surface_piddle() will return to use an anonymous array with a $piddle and $surface which we can use with PDL and SDL. PDL will be used to operate on the $piddle. SDL will be used to update the $surface and render it to the SDLx::App.

+ $app->add_move_handler( sub {
+
+   SDL::Video::lock_surface($surface);
+ 
+   $piddle->mslice( 'X',
+   [ rand(400), rand(400), 1 ],
+   [ rand(200), rand(200), 1 ] 
+   ) .= pdl( rand(225), rand(225), rand(225), 255 );
+
+   SDL::Video::unlock_surface($surface);
+ } );

SDL::Video::lock_surface prevents SDL from doing any operations on the $surface until SDL::Video::unlock_surface is called. Next we will blit this surface onto the $app.

In this case we use PDL to draw random rectangles of random color.

Running the App

Finally we blit the $surface and update the $app.

+ $app->add_show_handler( sub {
+
+    $surface->blit( $app, [0,0,$surface->w,$surface->h], [10,10,0,0] );
+    $app->update();
+
+ });

+ $app->run();

Complete Program

OpenGL

Perl OpenGL

Texturing

Using textures for OpenGL.

SDL surfaces as textures

Example.

POD ERRORS

Hey! The above document had some coding errors, which are explained below:

Around line 1:

Unknown directive: =head0