Submarine SDF with fake 3D effect, rendered by Ebiten

ebiten-gfx-submarine.go

package main

import (
	"github.com/hajimehoshi/ebiten"
	"github.com/peterhellberg/gfx"
)

func main() {
	s := NewSubmarine(112, 112, gfx.PaletteAmmo8)

	ebiten.SetFullscreen(false)
	ebiten.SetWindowDecorated(false)

	ebiten.Run(s.run, s.w, s.h, 5, "Ebiten GFX Submarine")
}

func NewSubmarine(w, h int, p gfx.Palette) *Submarine {
	c := gfx.BoundsCenter(gfx.IR(0, 0, -w, -h))

	return &Submarine{w: w, h: h, c: c, p: p, m: gfx.IM.Moved(c)}
}

type Submarine struct {
	w int
	h int
	t float64
	c gfx.Vec
	p gfx.Palette
	m gfx.Matrix

	deg float64
}

func (s *Submarine) run(screen *ebiten.Image) error {
	if err := s.update(); err != nil {
		return err
	}

	if ebiten.IsDrawingSkipped() {
		return nil
	}

	return screen.ReplacePixels(s.draw().Pixels())
}

func (s *Submarine) update() error {
	switch {
	case ebiten.IsKeyPressed(ebiten.KeyEscape) || ebiten.IsKeyPressed(ebiten.KeyQ):
		return gfx.ErrDone
	case ebiten.IsKeyPressed(ebiten.KeyLeft) || ebiten.IsKeyPressed(ebiten.KeyRight):
		if ebiten.IsKeyPressed(ebiten.KeyLeft) {
			if s.deg += 1; s.deg > 360 {
				s.deg = 0
			}

			if s.t < 9 {
				s.t += 0.1
			}
		}

		if ebiten.IsKeyPressed(ebiten.KeyRight) {
			if s.deg -= 1; s.deg < 0 {
				s.deg = 360
			}

			if s.t > -9 {
				s.t -= 0.1
			}
		}

		s.m = gfx.IM.Moved(s.c).RotatedDegrees(gfx.ZV, s.deg)
	default:
		if gfx.MathAbs(s.t) >= 0.1 {
			if s.t < 0 {
				s.t += 0.6
			} else {
				s.t -= 0.6
			}
		} else {
			s.t = 0
		}
	}

	return nil
}

func (s *Submarine) draw() *gfx.Paletted {
	m := gfx.NewPaletted(s.w, s.h, s.p, s.p[3])

	gfx.EachPixel(m.Bounds(), func(x, y int) {
		pm := s.m.Project(gfx.IV(x, y))
		sd := gfx.SignedDistance{pm}

		b := gfx.V(23-gfx.MathAbs(s.t), 8)

		d := sd.OpSubtraction(
			sd.OpMoved(gfx.V(-s.t, 22), sd.CircleFunc(6)),
			sd.OpUnion(
				sd.OpMoved(gfx.V(0, 26), sd.RectangleFunc(b)),
				sd.OpUnion(
					sd.OpMoved(gfx.V(0, -40), sd.CircleFunc(10)),
					sd.Rectangle(gfx.V(10, 37)),
				),
			),
		)

		if d < 2 {
			m.Set(x, y, s.p[1])
		}

		if d < 0 {
			m.Set(x, y, s.p[2])
		}
	})

	return m
}

https://i.imgur.com/4f8uGF5.mp4