mirror of
https://github.com/hajimehoshi/ebiten.git
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326 lines
8.4 KiB
Go
326 lines
8.4 KiB
Go
// Copyright 2019 The Ebiten Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//go:build example
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// +build example
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package main
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import (
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"bytes"
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"errors"
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"fmt"
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"image"
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"image/color"
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_ "image/png"
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"log"
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"math"
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"sort"
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"github.com/hajimehoshi/ebiten/v2"
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"github.com/hajimehoshi/ebiten/v2/ebitenutil"
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"github.com/hajimehoshi/ebiten/v2/examples/resources/images"
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"github.com/hajimehoshi/ebiten/v2/inpututil"
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)
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const (
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screenWidth = 240
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screenHeight = 240
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padding = 20
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)
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var (
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bgImage *ebiten.Image
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shadowImage = ebiten.NewImage(screenWidth, screenHeight)
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triangleImage = ebiten.NewImage(screenWidth, screenHeight)
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)
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func init() {
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// Decode image from a byte slice instead of a file so that
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// this example works in any working directory.
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// If you want to use a file, there are some options:
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// 1) Use os.Open and pass the file to the image decoder.
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// This is a very regular way, but doesn't work on browsers.
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// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
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// This works even on browsers.
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// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
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// This also works on browsers.
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img, _, err := image.Decode(bytes.NewReader(images.Tile_png))
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if err != nil {
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log.Fatal(err)
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}
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bgImage = ebiten.NewImageFromImage(img)
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triangleImage.Fill(color.White)
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}
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type line struct {
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X1, Y1, X2, Y2 float64
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}
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func (l *line) angle() float64 {
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return math.Atan2(l.Y2-l.Y1, l.X2-l.X1)
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}
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type object struct {
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walls []line
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}
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func (o object) points() [][2]float64 {
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// Get one of the endpoints for all segments,
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// + the startpoint of the first one, for non-closed paths
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var points [][2]float64
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for _, wall := range o.walls {
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points = append(points, [2]float64{wall.X2, wall.Y2})
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}
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p := [2]float64{o.walls[0].X1, o.walls[0].Y1}
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if p[0] != points[len(points)-1][0] && p[1] != points[len(points)-1][1] {
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points = append(points, [2]float64{o.walls[0].X1, o.walls[0].Y1})
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}
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return points
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}
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func newRay(x, y, length, angle float64) line {
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return line{
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X1: x,
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Y1: y,
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X2: x + length*math.Cos(angle),
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Y2: y + length*math.Sin(angle),
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}
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}
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// intersection calculates the intersection of given two lines.
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func intersection(l1, l2 line) (float64, float64, bool) {
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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)
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tNum := (l1.X1-l2.X1)*(l2.Y1-l2.Y2) - (l1.Y1-l2.Y1)*(l2.X1-l2.X2)
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uNum := -((l1.X1-l1.X2)*(l1.Y1-l2.Y1) - (l1.Y1-l1.Y2)*(l1.X1-l2.X1))
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if denom == 0 {
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return 0, 0, false
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}
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t := tNum / denom
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if t > 1 || t < 0 {
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return 0, 0, false
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}
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u := uNum / denom
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if u > 1 || u < 0 {
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return 0, 0, false
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}
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x := l1.X1 + t*(l1.X2-l1.X1)
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y := l1.Y1 + t*(l1.Y2-l1.Y1)
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return x, y, true
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}
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// rayCasting returns a slice of line originating from point cx, cy and intersecting with objects
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func rayCasting(cx, cy float64, objects []object) []line {
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const rayLength = 1000 // something large enough to reach all objects
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var rays []line
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for _, obj := range objects {
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// Cast two rays per point
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for _, p := range obj.points() {
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l := line{cx, cy, p[0], p[1]}
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angle := l.angle()
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for _, offset := range []float64{-0.005, 0.005} {
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points := [][2]float64{}
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ray := newRay(cx, cy, rayLength, angle+offset)
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// Unpack all objects
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for _, o := range objects {
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for _, wall := range o.walls {
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if px, py, ok := intersection(ray, wall); ok {
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points = append(points, [2]float64{px, py})
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}
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}
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}
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// Find the point closest to start of ray
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min := math.Inf(1)
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minI := -1
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for i, p := range points {
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d2 := (cx-p[0])*(cx-p[0]) + (cy-p[1])*(cy-p[1])
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if d2 < min {
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min = d2
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minI = i
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}
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}
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rays = append(rays, line{cx, cy, points[minI][0], points[minI][1]})
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}
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}
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}
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// Sort rays based on angle, otherwise light triangles will not come out right
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sort.Slice(rays, func(i int, j int) bool {
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return rays[i].angle() < rays[j].angle()
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})
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return rays
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}
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func (g *Game) handleMovement() {
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if ebiten.IsKeyPressed(ebiten.KeyD) || ebiten.IsKeyPressed(ebiten.KeyArrowRight) {
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g.px += 4
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}
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if ebiten.IsKeyPressed(ebiten.KeyS) || ebiten.IsKeyPressed(ebiten.KeyArrowDown) {
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g.py += 4
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}
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if ebiten.IsKeyPressed(ebiten.KeyA) || ebiten.IsKeyPressed(ebiten.KeyArrowLeft) {
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g.px -= 4
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}
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if ebiten.IsKeyPressed(ebiten.KeyW) || ebiten.IsKeyPressed(ebiten.KeyArrowUp) {
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g.py -= 4
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}
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// +1/-1 is to stop player before it reaches the border
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if g.px >= screenWidth-padding {
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g.px = screenWidth - padding - 1
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}
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if g.px <= padding {
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g.px = padding + 1
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}
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if g.py >= screenHeight-padding {
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g.py = screenHeight - padding - 1
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}
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if g.py <= padding {
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g.py = padding + 1
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}
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}
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func rayVertices(x1, y1, x2, y2, x3, y3 float64) []ebiten.Vertex {
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return []ebiten.Vertex{
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{DstX: float32(x1), DstY: float32(y1), SrcX: 0, SrcY: 0, ColorR: 1, ColorG: 1, ColorB: 1, ColorA: 1},
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{DstX: float32(x2), DstY: float32(y2), SrcX: 0, SrcY: 0, ColorR: 1, ColorG: 1, ColorB: 1, ColorA: 1},
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{DstX: float32(x3), DstY: float32(y3), SrcX: 0, SrcY: 0, ColorR: 1, ColorG: 1, ColorB: 1, ColorA: 1},
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}
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}
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type Game struct {
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showRays bool
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px, py int
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objects []object
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}
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func (g *Game) Update() error {
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if inpututil.IsKeyJustPressed(ebiten.KeyEscape) {
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return errors.New("game ended by player")
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}
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if inpututil.IsKeyJustPressed(ebiten.KeyR) {
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g.showRays = !g.showRays
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}
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g.handleMovement()
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return nil
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}
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func (g *Game) Draw(screen *ebiten.Image) {
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// Reset the shadowImage
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shadowImage.Fill(color.Black)
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rays := rayCasting(float64(g.px), float64(g.py), g.objects)
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// Subtract ray triangles from shadow
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opt := &ebiten.DrawTrianglesOptions{}
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opt.Address = ebiten.AddressRepeat
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opt.CompositeMode = ebiten.CompositeModeSourceOut
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for i, line := range rays {
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nextLine := rays[(i+1)%len(rays)]
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// Draw triangle of area between rays
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v := rayVertices(float64(g.px), float64(g.py), nextLine.X2, nextLine.Y2, line.X2, line.Y2)
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shadowImage.DrawTriangles(v, []uint16{0, 1, 2}, triangleImage, opt)
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}
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// Draw background
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screen.DrawImage(bgImage, nil)
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if g.showRays {
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// Draw rays
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for _, r := range rays {
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ebitenutil.DrawLine(screen, r.X1, r.Y1, r.X2, r.Y2, color.RGBA{255, 255, 0, 150})
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}
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}
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// Draw shadow
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op := &ebiten.DrawImageOptions{}
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op.ColorM.Scale(1, 1, 1, 0.7)
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screen.DrawImage(shadowImage, op)
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// Draw walls
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for _, obj := range g.objects {
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for _, w := range obj.walls {
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ebitenutil.DrawLine(screen, w.X1, w.Y1, w.X2, w.Y2, color.RGBA{255, 0, 0, 255})
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}
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}
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// Draw player as a rect
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ebitenutil.DrawRect(screen, float64(g.px)-2, float64(g.py)-2, 4, 4, color.Black)
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ebitenutil.DrawRect(screen, float64(g.px)-1, float64(g.py)-1, 2, 2, color.RGBA{255, 100, 100, 255})
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if g.showRays {
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ebitenutil.DebugPrintAt(screen, "R: hide rays", padding, 0)
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} else {
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ebitenutil.DebugPrintAt(screen, "R: show rays", padding, 0)
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}
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ebitenutil.DebugPrintAt(screen, "WASD: move", 160, 0)
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ebitenutil.DebugPrintAt(screen, fmt.Sprintf("TPS: %0.2f", ebiten.CurrentTPS()), 51, 51)
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ebitenutil.DebugPrintAt(screen, fmt.Sprintf("Rays: 2*%d", len(rays)/2), padding, 222)
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}
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func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
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return screenWidth, screenHeight
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}
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func rect(x, y, w, h float64) []line {
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return []line{
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{x, y, x, y + h},
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{x, y + h, x + w, y + h},
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{x + w, y + h, x + w, y},
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{x + w, y, x, y},
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}
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}
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func main() {
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g := &Game{
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px: screenWidth / 2,
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py: screenHeight / 2,
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}
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// Add outer walls
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g.objects = append(g.objects, object{rect(padding, padding, screenWidth-2*padding, screenHeight-2*padding)})
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// Angled wall
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g.objects = append(g.objects, object{[]line{{50, 110, 100, 150}}})
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// Rectangles
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g.objects = append(g.objects, object{rect(45, 50, 70, 20)})
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g.objects = append(g.objects, object{rect(150, 50, 30, 60)})
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ebiten.SetWindowSize(screenWidth*2, screenHeight*2)
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ebiten.SetWindowTitle("Ray casting and shadows (Ebiten demo)")
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if err := ebiten.RunGame(g); err != nil {
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log.Fatal(err)
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}
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}
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