pdl.pl

use strict;
use warnings;

use PDL;
use PDL::Matrix 'mpdl';
use PDL::Core 'howbig';

my $pIndices = pdl(    #
	0, 3, 1,
	1, 3, 2,
	2, 3, 0,
	1, 2, 0,
)->long;

my $pVertices = mpdl(    #
	[ -1, -1, 0.5773,   0,   0, 0, 0, 0 ],
	[ 0,  -1, -1.15475, 0.5, 0, 0, 0, 0 ],
	[ 1,  -1, 0.5773,   1,   0, 0, 0, 0 ],
	[ 0,  1,  0,        0.5, 1, 0, 0, 0 ],
)->float;

# Accumulate each triangle normal into each of the triangle vertices
for ( my $i = 0 ; $i < $pIndices->nelem ; $i += 3 ) {
	my $Index0 = $pIndices->at( $i );
	my $Index1 = $pIndices->at( $i + 1 );
	my $Index2 = $pIndices->at( $i + 2 );
	my $v1     = $pVertices->slice( "($Index1),0:2" ) - $pVertices->slice( "($Index0),0:2" );
	my $v2     = $pVertices->slice( "($Index2),0:2" ) - $pVertices->slice( "($Index0),0:2" );
	my $Normal = $v1->crossp( $v2 );
	$Normal = $Normal->norm;
	print $Normal;

	$pVertices->slice( "($Index0),5:7" ) += $Normal;
	$pVertices->slice( "($Index1),5:7" ) += $Normal;
	$pVertices->slice( "($Index2),5:7" ) += $Normal;
}

# Normalize all the vertex normals
for my $i ( 0 .. $pVertices->dim( 0 ) - 1 ) {
	$pVertices->slice( "($i),5:7" ) = $pVertices->slice( "($i),5:7" )->norm;
}