Initial commit

render/raycaster.go

@@ -0,0 +1,85 @@
+package render
+
+import (
+	stdmath "math"
+
+	"github.com/pnx/go-raytracer/math"
+	"github.com/pnx/go-raytracer/world"
+)
+
+type RayHit struct {
+	Cell     math.Vec2u8
+	Side     int
+	Distance float64
+	Pos      math.Vec2f
+}
+
+func CastRay(camera math.Transform, level *world.Level, x int, max_rays int) RayHit {
+	angle := camera.Direction.Get()
+	cameraX := 2*float64(x)/float64(max_rays) - 1
+	rayDirX := stdmath.Cos(angle) + cameraX*stdmath.Cos(angle+stdmath.Pi/2)
+	rayDirY := stdmath.Sin(angle) + cameraX*stdmath.Sin(angle+stdmath.Pi/2)
+
+	mapX := int(camera.X) / world.TileSize
+	mapY := int(camera.Y) / world.TileSize
+
+	deltaDistX := stdmath.Abs(1 / rayDirX)
+	deltaDistY := stdmath.Abs(1 / rayDirY)
+
+	var stepX, stepY int
+	var sideDistX, sideDistY float64
+
+	if rayDirX < 0 {
+		stepX = -1
+		sideDistX = (float64(camera.X)/world.TileSize - float64(mapX)) * deltaDistX
+	} else {
+		stepX = 1
+		sideDistX = (float64(mapX+1) - float64(camera.X)/world.TileSize) * deltaDistX
+	}
+	if rayDirY < 0 {
+		stepY = -1
+		sideDistY = (float64(camera.Y)/world.TileSize - float64(mapY)) * deltaDistY
+	} else {
+		stepY = 1
+		sideDistY = (float64(mapY+1) - float64(camera.Y)/world.TileSize) * deltaDistY
+	}
+
+	// DDA loop
+	var side int // 0 = x, 1 = y
+	for {
+		if sideDistX < sideDistY {
+			sideDistX += deltaDistX
+			mapX += stepX
+			side = 0
+		} else {
+			sideDistY += deltaDistY
+			mapY += stepY
+			side = 1
+		}
+
+		if mapX < 0 || mapX >= level.W || mapY < 0 || mapY >= level.H {
+			break // out of bounds
+		}
+		if level.Wall(mapX, mapY) {
+			break
+		}
+	}
+
+	// Calculate distance to wall
+	var perpWallDist float64
+	if side == 0 {
+		perpWallDist = (float64(mapX) - float64(camera.X)/world.TileSize + float64(1-stepX)/2) / rayDirX
+	} else {
+		perpWallDist = (float64(mapY) - float64(camera.Y)/world.TileSize + float64(1-stepY)/2) / rayDirY
+	}
+
+	return RayHit{
+		Cell:     math.Vec2u8{X: uint8(mapX), Y: uint8(mapY)},
+		Side:     side,
+		Distance: perpWallDist,
+		Pos: math.Vec2f{
+			X: rayDirX * perpWallDist,
+			Y: rayDirY * perpWallDist,
+		},
+	}
+}