user
Task

Draw a rotating cube.

It should be oriented with one vertex pointing straight up, and its opposite vertex on the main diagonal (the one farthest away) straight down. It can be solid or wire-frame, and you can use ASCII art if your language doesn't have graphical capabilities. Perspective is optional.

Related tasks

* Draw a cuboid
* write language name in 3D ASCII
assistant
(formerly Perl 6)

**Works with**: Rakudo version 2018.12

Raku has no native graphics libraries built in, but makes it fairly easy to bind to third party libraries. Here we'll use bindings to Libcaca, the **C**olor **A**S**C**II **A**rt library to generate a rotating cube in an ASCII terminal.

```
use Terminal::Caca;
given my $canvas = Terminal::Caca.new {
    .title('Rosetta Code - Rotating cube - Press any key to exit');

    sub scale-and-translate($x, $y, $z) {
        $x * 5 / ( 5 + $z ) * 15 + 40,
        $y * 5 / ( 5 + $z ) *  7 + 15,
        $z;
    }

    sub rotate3d-x( $x, $y, $z, $angle ) {
        my ($cosθ, $sinθ) = cis( $angle * π / 180.0 ).reals;
        $x,
        $y * $cosθ - $z * $sinθ,
        $y * $sinθ + $z * $cosθ;
    }

    sub rotate3d-y( $x, $y, $z, $angle ) {
        my ($cosθ, $sinθ) = cis( $angle * π / 180.0 ).reals;
        $x * $cosθ - $z * $sinθ,
        $y,
        $x * $sinθ + $z * $cosθ;
    }

    sub rotate3d-z( $x, $y, $z, $angle ) {
        my ($cosθ, $sinθ) = cis( $angle * π / 180.0 ).reals;
        $x * $cosθ - $y * $sinθ,
        $x * $cosθ + $y * $sinθ,
        $z;
    }

    # Unit cube from polygon mesh, aligned to axes
    my @mesh =
      [ [1, 1, -1], [-1, -1, -1], [-1,  1, -1] ], # far face
      [ [1, 1, -1], [-1, -1, -1], [ 1, -1, -1] ],
      [ [1, 1,  1], [-1, -1,  1], [-1,  1,  1] ], # near face
      [ [1, 1,  1], [-1, -1,  1], [ 1, -1,  1] ];
      @mesh.push: [$_».rotate( 1)».Array] for @mesh[^4]; # positive and
      @mesh.push: [$_».rotate(-1)».Array] for @mesh[^4]; # negative rotations

    # Rotate to correct orientation for task
    for ^@mesh X ^@mesh[0] -> ($i, $j) {
        @(@mesh[$i;$j]) = rotate3d-x |@mesh[$i;$j], 45;
        @(@mesh[$i;$j]) = rotate3d-z |@mesh[$i;$j], 40;
    }

    my @colors = red, blue, green, cyan, magenta, yellow;

    loop {
        for ^359 -> $angle {
            .color( white, white );
            .clear;

            # Flatten 3D into 2D and rotate for all faces
            my @faces-z;
            my $c-index = 0;
            for @mesh -> @triangle {
                my @points;
                my $sum-z = 0;
                for @triangle -> @node {
                    my ($px, $py, $z) = scale-and-translate |rotate3d-y |@node, $angle;
                    @points.append: $px.Int, $py.Int;
                    $sum-z += $z;
                }

                @faces-z.push: %(
                    color  => @colors[$c-index++ div 2],
                    points => @points,
                    avg-z  => $sum-z / +@points;
                );
            }

            # Draw all faces
            # Sort by z to draw farthest first
            for @faces-z.sort( -*.<avg-z> ) -> %face {
                # Draw filled triangle
                .color( %face<color>, %face<color> );
                .fill-triangle( |%face<points> );
                # And frame
                .color( black, black );
                .thin-triangle( |%face<points> );
            }

            .refresh;
            exit if .wait-for-event(key-press);
        }
    }

    # Cleanup on scope exit
    LEAVE {
        .cleanup;
    }
}

```