Twisting column using gui (and gfx) inspired by https://trasevol.dog/2018/01/24/di20/

gui-twisting-column.go

package main

import (
	"image"
	"image/draw"
	"time"

	"github.com/peterhellberg/gfx"
	"github.com/peterhellberg/gui"
)

var start = time.Now()

func main() {
	gui.Run(loop)
}

func loop() {
	win, err := gui.Open(
		gui.Title("gui-twisting-column"),
		gui.Size(512, 512),
		gui.Decorated(false),
		gui.Resizable(false),
	)
	if err != nil {
		panic(err)
	}

	ticker := time.NewTicker(32 * time.Millisecond)

	go func() {
		for t := range ticker.C {
			win.Send(gui.EventUpdate{t})
		}
	}()

	for event := range win.Events() {
		switch event := event.(type) {
		case gui.EventClose:
			ticker.Stop()
			win.Close()
		case gui.EventKeyboardDown:
			if event.Key == "escape" {
				ticker.Stop()
				win.Close()
			}
		case gui.EventKeyboardChar:
			if event.Char == 'q' {
				ticker.Stop()
				win.Close()
			}
		case gui.EventUpdate:
			win.Draw(update)
		}
	}
}

func update(dst draw.Image) image.Rectangle {
	m := gfx.NewImage(128, 128)

	t := time.Since(start).Seconds() / 3

	for y := 0.0; y < 127; y++ {
		yy := y / 1024

		a := cos(0.2*sin(t*0.1+yy*2)) + 0.5*cos(-0.2*t+yy/2)

		for i := 0.0; i <= 0.75; i += 0.25 {
			x1 := 64 + 32*cos(a+i+0.25)
			x2 := 64 + 32*cos(a+i)

			if x1 < x2 {
				gfx.DrawLineBresenham(m, gfx.V(x1, y), gfx.V(x2, y), gfx.ColorWhite)

				gfx.SetVec(m, gfx.V(x1, y), gfx.ColorBlack)
				gfx.SetVec(m, gfx.V(x2, y), gfx.ColorBlack)
			}
		}
	}

	s := gfx.NewScaledImage(m, 4)

	gfx.DrawSrc(dst, s.Bounds(), s, gfx.ZP)

	return dst.Bounds()
}

const tau = gfx.Pi * 2

func cos(x float64) float64 {
	return gfx.MathCos(x * tau)
}

func sin(x float64) float64 {
	return gfx.MathSin(x * tau)
}

Not drawing the black outline

package main

import (
	"image"
	"image/draw"
	"time"

	"github.com/peterhellberg/gfx"
	"github.com/peterhellberg/gui"
)

var start = time.Now()

func main() {
	gui.Run(loop)
}

func loop() {
	win, err := gui.Open(
		gui.Title("gui-twisting-column"),
		gui.Size(1024, 1024),
		gui.Decorated(false),
		gui.Resizable(false),
	)
	if err != nil {
		panic(err)
	}

	ticker := time.NewTicker(48 * time.Millisecond)

	go func() {
		for t := range ticker.C {
			win.Send(gui.EventUpdate{t})
		}
	}()

	for event := range win.Events() {
		switch event := event.(type) {
		case gui.EventClose:
			ticker.Stop()
			win.Close()
		case gui.EventKeyboardDown:
			if event.Key == "escape" {
				win.Send(gui.EventClose{})
			}
		case gui.EventKeyboardChar:
			if event.Char == 'q' {
				win.Send(gui.EventClose{})
			}
		case gui.EventUpdate:
			win.Draw(update)
		}
	}
}

func update(dst draw.Image) image.Rectangle {
	m := gfx.NewImage(512, 512)

	t := time.Since(start).Seconds() / 3

	for y := 0.0; y < 512; y++ {
		yy := y / 4096

		a := cos(0.2*sin(t*0.1+yy*2)) + 0.5*cos(-0.2*t+yy/2)

		for i := 0.0; i <= 0.75; i += 0.25 {
			x1 := 256 + 128*cos(a+i+0.25)
			x2 := 256 + 128*cos(a+i)

			if x1 < x2 {
				for x := x1; x < x2; x++ {
					v := gfx.V(x, y)
					n := v.To(gfx.V(x1, y)).Len() / 256
					c := gfx.PaletteEDG8.At(n)

					gfx.SetVec(m, v, c)
				}

				gfx.SetVec(m, gfx.V(x1, y), gfx.ColorBlack)
				gfx.SetVec(m, gfx.V(x2, y), gfx.ColorBlack)
			}
		}
	}

	gfx.DrawSrc(dst, m.Bounds().Add(gfx.Pt(256, 256)), m, gfx.ZP)

	return dst.Bounds()
}

const tau = gfx.Pi * 2

func cos(x float64) float64 {
	return gfx.MathCos(x * tau)
}

func sin(x float64) float64 {
	return gfx.MathSin(x * tau)
}