non-textured-raycaster.go

package main

import (
	"fmt"
	"github.com/hajimehoshi/ebiten/v2"
	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
	"image/color"
	"log"
	"math"
)

const (
	screenWidth  = 640
	screenHeight = 480
	mapWidth     = 24
	mapHeight    = 24
)

var worldMap = [mapWidth][mapHeight]int{
	{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 2, 2, 2, 2, 2, 0, 0, 0, 0, 3, 0, 3, 0, 3, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 3, 0, 0, 0, 3, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 2, 2, 0, 2, 2, 0, 0, 0, 0, 3, 0, 3, 0, 3, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 4, 4, 4, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 4, 0, 4, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 4, 0, 0, 0, 0, 5, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 4, 0, 4, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 4, 0, 4, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 4, 4, 4, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
	{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
}

type Game struct {
	posX, posY     float64
	dirX, dirY     float64
	planeX, planeY float64
}

func NewGame() *Game {
	return &Game{
		posX:   22,
		posY:   12,
		dirX:   -1,
		dirY:   0,
		planeX: 0,
		planeY: 0.66,
	}
}

func (g *Game) Update() error {
	frameTime := 1.0 / 60.0 // Assuming 60 FPS

	moveSpeed := frameTime * 5.0
	rotSpeed := frameTime * 3.0

	if ebiten.IsKeyPressed(ebiten.KeyW) {
		if worldMap[int(g.posX+g.dirX*moveSpeed)][int(g.posY)] == 0 {
			g.posX += g.dirX * moveSpeed
		}
		if worldMap[int(g.posX)][int(g.posY+g.dirY*moveSpeed)] == 0 {
			g.posY += g.dirY * moveSpeed
		}
	}
	if ebiten.IsKeyPressed(ebiten.KeyS) {
		if worldMap[int(g.posX-g.dirX*moveSpeed)][int(g.posY)] == 0 {
			g.posX -= g.dirX * moveSpeed
		}
		if worldMap[int(g.posX)][int(g.posY-g.dirY*moveSpeed)] == 0 {
			g.posY -= g.dirY * moveSpeed
		}
	}
	if ebiten.IsKeyPressed(ebiten.KeyD) {
		oldDirX := g.dirX
		g.dirX = g.dirX*math.Cos(-rotSpeed) - g.dirY*math.Sin(-rotSpeed)
		g.dirY = oldDirX*math.Sin(-rotSpeed) + g.dirY*math.Cos(-rotSpeed)
		oldPlaneX := g.planeX
		g.planeX = g.planeX*math.Cos(-rotSpeed) - g.planeY*math.Sin(-rotSpeed)
		g.planeY = oldPlaneX*math.Sin(-rotSpeed) + g.planeY*math.Cos(-rotSpeed)
	}
	if ebiten.IsKeyPressed(ebiten.KeyA) {
		oldDirX := g.dirX
		g.dirX = g.dirX*math.Cos(rotSpeed) - g.dirY*math.Sin(rotSpeed)
		g.dirY = oldDirX*math.Sin(rotSpeed) + g.dirY*math.Cos(rotSpeed)
		oldPlaneX := g.planeX
		g.planeX = g.planeX*math.Cos(rotSpeed) - g.planeY*math.Sin(rotSpeed)
		g.planeY = oldPlaneX*math.Sin(rotSpeed) + g.planeY*math.Cos(rotSpeed)
	}

	return nil
}

func (g *Game) Draw(screen *ebiten.Image) {
	screen.Fill(color.RGBA{0, 0, 0, 255})

	for x := 0; x < screenWidth; x++ {
		cameraX := 2*float64(x)/float64(screenWidth) - 1
		rayDirX := g.dirX + g.planeX*cameraX
		rayDirY := g.dirY + g.planeY*cameraX

		mapX := int(g.posX)
		mapY := int(g.posY)

		var sideDistX, sideDistY float64

		deltaDistX := math.Abs(1 / rayDirX)
		deltaDistY := math.Abs(1 / rayDirY)

		var perpWallDist float64

		var stepX, stepY int
		hit := 0
		var side int

		if rayDirX < 0 {
			stepX = -1
			sideDistX = (g.posX - float64(mapX)) * deltaDistX
		} else {
			stepX = 1
			sideDistX = (float64(mapX) + 1.0 - g.posX) * deltaDistX
		}
		if rayDirY < 0 {
			stepY = -1
			sideDistY = (g.posY - float64(mapY)) * deltaDistY
		} else {
			stepY = 1
			sideDistY = (float64(mapY) + 1.0 - g.posY) * deltaDistY
		}

		for hit == 0 {
			if sideDistX < sideDistY {
				sideDistX += deltaDistX
				mapX += stepX
				side = 0
			} else {
				sideDistY += deltaDistY
				mapY += stepY
				side = 1
			}
			if worldMap[mapX][mapY] > 0 {
				hit = 1
			}
		}

		if side == 0 {
			perpWallDist = sideDistX - deltaDistX
		} else {
			perpWallDist = sideDistY - deltaDistY
		}

		lineHeight := int(float64(screenHeight) / perpWallDist)

		drawStart := -lineHeight/2 + screenHeight/2
		if drawStart < 0 {
			drawStart = 0
		}
		drawEnd := lineHeight/2 + screenHeight/2
		if drawEnd >= screenHeight {
			drawEnd = screenHeight - 1
		}

		col := getColor(worldMap[mapX][mapY], side)

		ebitenutil.DrawLine(screen, float64(x), float64(drawStart), float64(x), float64(drawEnd), col)
	}

	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f", ebiten.CurrentFPS()))
}

func getColor(value int, side int) color.Color {
	var col color.RGBA
	switch value {
	case 1:
		col = color.RGBA{255, 0, 0, 255} // Red
	case 2:
		col = color.RGBA{0, 255, 0, 255} // Green
	case 3:
		col = color.RGBA{0, 0, 255, 255} // Blue
	case 4:
		col = color.RGBA{255, 255, 255, 255} // White
	default:
		col = color.RGBA{255, 255, 0, 255} // Yellow
	}

	if side == 1 {
		col.R /= 2
		col.G /= 2
		col.B /= 2
	}

	return col
}

func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
	return screenWidth, screenHeight
}

func main() {
	ebiten.SetWindowSize(screenWidth, screenHeight)
	ebiten.SetWindowTitle("Raycaster in Ebiten")

	if err := ebiten.RunGame(NewGame()); err != nil {
		log.Fatal(err)
	}
}