# Comment

MATERIAL "id"               # Material definition with unique name
tex      "semantic" "image"      # Texture semantic (e.g. diffuse, normal, specular) to file mapping


# Mesh with name, transformation matrix and optional parent
MESH "name"/tm0/tm1/tm2/tm3/tm4/tm5/tm6/tm7/tm8/tm9/tm10/tm11/tm12/tm13/tm14/tm15/["parent"]
v      x/y/z               # Vertex position
vt0      u/v               # Vertex texture coordinate set 0
vt1      u/v               # Vertex texture coordinate set 1 (optional, but must match vt0 if defined)
vn      x/y/z               # Vertex normal
vs      "joint"/weight ["joint"/weight]
usemtl   "ref_mtl_id"                 # Bind a material for the following faces
f       v/vt/vn/vs v/vt/vn/vs v/vt/vn/vs   # Face indexing vertex data
defmorph "name"               # Morph target definition for mesh
mv       x/y/z               # Vertex position
mvn      x/y/z               # Vertex normal
m       v/mv/mvn            # Morph-Vertex


# Joint with name, parent, inverse bind matrix and transformation
JOINT "name"/"parent"/bm0/bm1/bm2/bm3/bm4/bm5/bm6/bm7/bm8/bm9/bm10/bm11/bm12/bm13/bm14/bm15/tm0/tm1/tm2/tm3/tm4/tm5/tm6/tm7/tm8/tm9/tm10/tm11/tm12/tm13/tm14/tm15

# find vertices with same coordinates, this is for normal smoothing, return of list of matching indices
sub find_same_vertices {
    my $object      = shift;
    my $indices_map = shift;
    my $index       = shift;

    my $vertex = $object->{numvert}->[$index];

    return @{ $indices_map->{ $vertex->as_string } };
}

# create map of indices with same vertices
sub make_indices_map {
    my $object = shift;

    my %indices_map;

    foreach my $surface ( @{ $object->{numsurf} } ) {

        # only average out smooth vertex normals
        next if ( $surface->{SURF}->{shading} ne 'smooth' );
        foreach my $ref ( @{ $surface->{refs} } ) {
            my $v = $object->{numvert}->[ $ref->{index} ];
            push @{ $indices_map{ $v->as_string } }, $ref->{index};
        }
    }

    return \%indices_map;
}

sub calc_vertex_normals {
    my $object = shift;

    warn "calculating normals: $object->{name}\n";

    my @normals;
    my @tangents;
    my @bitangents;

    my $indices_map = make_indices_map($object);

    foreach my $surface ( @{ $object->{numsurf} } ) {

        my $index0 = $surface->{refs}->[0]->{index};
        my $index1 = $surface->{refs}->[1]->{index};
        my $index2 = $surface->{refs}->[2]->{index};

        my $v0 = $object->{numvert}->[$index0];
        my $v1 = $object->{numvert}->[$index1];
        my $v2 = $object->{numvert}->[$index2];

        my $d0 = $v1 - $v0;
        my $d1 = $v2 - $v0;
        my $v  = ( $d0 x $d1 )->normalized;

        #
        #  Calculate the normal,tangent and bitangent for this face and add it
        #  to the running sum of normals for each of the
        #  vertices involved
        #

        my $Edge0uv = uv_sub( $surface->{refs}->[1], $surface->{refs}->[0] );
        my $Edge1uv = uv_sub( $surface->{refs}->[2], $surface->{refs}->[0] );

        my $cp = $Edge0uv->{u} * $Edge1uv->{v} - $Edge1uv->{u} * $Edge0uv->{v};
        my $r  = 0;
        if ( $cp != 0 ) {
            $r = 1.0 / $cp;
        }

        my $tangent   = ( $d0 * $Edge1uv->{v} - $d1 * $Edge0uv->{v} ) * $r;
        my $bitangent = ( $d1 * $Edge0uv->{u} - $d0 * $Edge1uv->{u} ) * $r;

        my @indices;
        push @indices, find_same_vertices( $object, $indices_map, $index0 );
        push @indices, find_same_vertices( $object, $indices_map, $index1 );
        push @indices, find_same_vertices( $object, $indices_map, $index2 );
        foreach my $index (@indices) {
            $normals[$index]    ||= vec3();
            $tangents[$index]   ||= vec3();
            $bitangents[$index] ||= vec3();

            $normals[$index]    += $v;
            $tangents[$index]   += $tangent;
            $bitangents[$index] += $bitangent;
        }
    }

    #  Normalize and fixup the vertex normal vectors, tangents en bitangents
    my $numVerts = int( @{ $object->{numvert} } );
    for ( my $j = 0 ; $j < $numVerts ; $j++ ) {
        my $n = $normals[$j]->normalized;
        my $t = $tangents[$j];

        # orthogonalize
        $tangents[$j] = ( $t - $n * ( $n * $t ) )->normalized;
        $normals[$j] = $n;

        if ( ( $n x $t ) * $bitangents[$j] < 0 ) {
            $bitangents[$j] = ( $n * -1 ) x $t;
        }
        else {
            $bitangents[$j] = $n x $t;
        }
    }

    $object->{normals}    = \@normals;
    $object->{tangents}   = \@tangents;
    $object->{bitangents} = \@bitangents;
}