ebiten/examples/raycasting/main.go

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// Copyright 2019 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// +build example jsgo
package main
import (
"bytes"
"errors"
"fmt"
"image"
"image/color"
_ "image/png"
"log"
"math"
"sort"
"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
"github.com/hajimehoshi/ebiten/examples/resources/images"
"github.com/hajimehoshi/ebiten/inpututil"
)
const (
screenWidth = 240
screenHeight = 240
)
var (
bgImage *ebiten.Image
shadowImage *ebiten.Image
triangleImage *ebiten.Image
)
func init() {
// Decode image from a byte slice instead of a file so that
// this example works in any working directory.
// If you want to use a file, there are some options:
// 1) Use os.Open and pass the file to the image decoder.
// This is a very regular way, but doesn't work on browsers.
// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
// This works even on browsers.
// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
// This also works on browsers.
img, _, err := image.Decode(bytes.NewReader(images.Tile_png))
if err != nil {
log.Fatal(err)
}
bgImage, _ = ebiten.NewImageFromImage(img, ebiten.FilterDefault)
shadowImage, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterDefault)
triangleImage, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterDefault)
triangleImage.Fill(color.White)
}
type Line struct {
X1, Y1, X2, Y2 float64
}
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func (l *Line) angle() float64 {
return math.Atan2(l.Y2-l.Y1, l.X2-l.X1)
}
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func newRay(x, y, length, angle float64) Line {
return Line{
X1: x,
Y1: y,
X2: x + length*math.Cos(angle),
Y2: y + length*math.Sin(angle),
}
}
// intersection calculates the intersection of given two lines.
func intersection(l1, l2 Line) (float64, float64, error) {
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// https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection#Given_two_points_on_each_line
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denom := (l1.X1-l1.X2)*(l2.Y1-l2.Y2) - (l1.Y1-l1.Y2)*(l2.X1-l2.X2)
tNum := (l1.X1-l2.X1)*(l2.Y1-l2.Y2) - (l1.Y1-l2.Y1)*(l2.X1-l2.X2)
uNum := -((l1.X1-l1.X2)*(l1.Y1-l2.Y1) - (l1.Y1-l1.Y2)*(l1.X1-l2.X1))
if denom == 0 {
return 0, 0, errors.New("lines parallel or coincident")
}
t := tNum / denom
if t > 1 || t < 0 {
return 0, 0, errors.New("lines intersect, segments do not")
}
u := uNum / denom
if u > 1 || u < 0 {
return 0, 0, errors.New("lines intersect, segments do not")
}
x := l1.X1 + t*(l1.X2-l1.X1)
y := l1.Y1 + t*(l1.Y2-l1.Y1)
return x, y, nil
}
// rayCasting returns a slice of Line originating from point cx, cy and intersecting with objects
func rayCasting(cx, cy float64, objects [][]Line) []Line {
var rays []Line
const rayLength = 1000 // something large enough to reach all objects
for _, obj := range objects {
// Get one of the endpoints for all segments,
// + the startpoint of the first one, for non-closed paths
var objPoints [][2]float64
for _, wall := range obj {
objPoints = append(objPoints, [2]float64{wall.X2, wall.Y2})
}
objPoints = append(objPoints, [2]float64{obj[0].X1, obj[0].Y1})
// Cast two rays per point
for _, p := range objPoints {
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l := Line{cx, cy, p[0], p[1]}
angle := l.angle()
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for _, offset := range []float64{-0.005, 0.005} {
points := [][2]float64{}
ray := newRay(cx, cy, rayLength, angle+offset)
// Unpack all objects
for _, o := range objects {
for _, wall := range o {
if px, py, err := intersection(ray, wall); err == nil {
points = append(points, [2]float64{px, py})
}
}
}
// Find the point closest to start of ray
min := math.Inf(1)
var minI = -1
for i, p := range points {
d2 := (cx-p[0])*(cx-p[0]) + (cy-p[1])*(cy-p[1])
if d2 < min {
min = d2
minI = i
}
}
rays = append(rays, Line{cx, cy, points[minI][0], points[minI][1]})
}
}
}
// Sort rays based on angle, otherwise light triangles will not come out right
sort.Slice(rays, func(i int, j int) bool {
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return rays[i].angle() < rays[j].angle()
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})
return rays
}
func vertices(x1, y1, x2, y2, x3, y3 float64) []ebiten.Vertex {
return []ebiten.Vertex{
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{float32(x1), float32(y1), 0, 0, 1, 1, 1, 1},
{float32(x2), float32(y2), 0, 0, 1, 1, 1, 1},
{float32(x3), float32(y3), 0, 0, 1, 1, 1, 1},
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}
}
func rect(x, y, w, h float64) []Line {
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return []Line{
{x, y, x, y + h},
{x, y + h, x + w, y + h},
{x + w, y + h, x + w, y},
{x + w, y, x, y},
}
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}
func handleMovement() {
if ebiten.IsKeyPressed(ebiten.KeyD) || ebiten.IsKeyPressed(ebiten.KeyRight) {
px += 4
}
if ebiten.IsKeyPressed(ebiten.KeyS) || ebiten.IsKeyPressed(ebiten.KeyDown) {
py += 4
}
if ebiten.IsKeyPressed(ebiten.KeyA) || ebiten.IsKeyPressed(ebiten.KeyLeft) {
px -= 4
}
if ebiten.IsKeyPressed(ebiten.KeyW) || ebiten.IsKeyPressed(ebiten.KeyUp) {
py -= 4
}
// +1/-1 is to stop player before it reaches the border
if px >= screenHeight-padding {
px = screenHeight - padding - 1
}
if px <= padding {
px = padding + 1
}
if py >= screenWidth-padding {
py = screenWidth - padding - 1
}
if py <= padding {
py = padding + 1
}
}
func update(screen *ebiten.Image) error {
if inpututil.IsKeyJustPressed(ebiten.KeyEscape) {
return errors.New("game ended by player")
}
if inpututil.IsKeyJustPressed(ebiten.KeyR) {
showRays = !showRays
}
handleMovement()
if ebiten.IsDrawingSkipped() {
return nil
}
// Reset the shadowImage
shadowImage.Fill(color.Black)
rays := rayCasting(px, py, objects)
// Subtract ray triangles from shadow
opt := &ebiten.DrawTrianglesOptions{}
opt.Address = ebiten.AddressRepeat
opt.CompositeMode = ebiten.CompositeModeSourceOut
for i, line := range rays {
nextLine := rays[(i+1)%len(rays)]
// Draw triangle of area between rays
v := vertices(px, py, nextLine.X2, nextLine.Y2, line.X2, line.Y2)
shadowImage.DrawTriangles(v, []uint16{0, 1, 2}, triangleImage, opt)
}
// Draw background
screen.DrawImage(bgImage, &ebiten.DrawImageOptions{})
if showRays {
// Draw rays
for _, r := range rays {
ebitenutil.DrawLine(screen, r.X1, r.Y1, r.X2, r.Y2, color.RGBA{255, 255, 0, 150})
}
}
// Draw shadow
op := &ebiten.DrawImageOptions{}
op.ColorM.Scale(1, 1, 1, 0.7)
screen.DrawImage(shadowImage, op)
// Draw walls
for _, wall := range objects {
for _, w := range wall {
ebitenutil.DrawLine(screen, w.X1, w.Y1, w.X2, w.Y2, color.RGBA{255, 0, 0, 255})
}
}
// Draw player as a rect
ebitenutil.DrawRect(screen, px-2, py-2, 4, 4, color.Black)
ebitenutil.DrawRect(screen, px-1, py-1, 2, 2, color.RGBA{255, 100, 100, 255})
if showRays {
ebitenutil.DebugPrintAt(screen, "R: hide rays", padding, 0)
} else {
ebitenutil.DebugPrintAt(screen, "R: show rays", padding, 0)
}
ebitenutil.DebugPrintAt(screen, "WASD: move", 160, 0)
ebitenutil.DebugPrintAt(screen, fmt.Sprintf("TPS: %0.2f", ebiten.CurrentTPS()), 51, 51)
return nil
}
var (
showRays bool
px, py float64
objects [][]Line
)
const padding = 20
func main() {
px = screenWidth / 2
py = screenHeight / 2
// Add outer walls
objects = append(objects, rect(padding, padding, screenWidth-2*padding, screenHeight-2*padding))
// Angled wall
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objects = append(objects, []Line{{50, 110, 100, 150}})
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// Rectangles
objects = append(objects, rect(45, 50, 70, 20))
objects = append(objects, rect(150, 50, 30, 60))
if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Ray casting and shadows (Ebiten demo)"); err != nil {
log.Fatal(err)
}
}