ebiten/examples/airship/main.go

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// Copyright 2016 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
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package main
import (
"fmt"
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"image"
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"image/color"
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_ "image/jpeg"
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"log"
"math"
"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
)
const (
screenWidth = 320
screenHeight = 240
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groundWidth = screenWidth + 70
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maxAngle = 256
maxLean = 16
)
var (
skyColor = color.RGBA{0x66, 0xcc, 0xff, 0xff}
thePlayer = &player{
x16: 16 * 100,
y16: 16 * 200,
angle: maxAngle * 3 / 4,
}
gophersImage *ebiten.Image
repeatedGophersImage *ebiten.Image
groundImage *ebiten.Image
fogImage *ebiten.Image
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)
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func init() {
var err error
gophersImage, _, err = ebitenutil.NewImageFromFile("_resources/images/gophers.jpg", ebiten.FilterNearest)
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if err != nil {
panic(err)
}
groundImage, _ = ebiten.NewImage(groundWidth, screenHeight*2/3+50, ebiten.FilterNearest)
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const repeat = 5
w, h := gophersImage.Size()
repeatedGophersImage, _ = ebiten.NewImage(w*repeat, h*repeat, ebiten.FilterNearest)
for j := 0; j < repeat; j++ {
for i := 0; i < repeat; i++ {
op := &ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(w*i), float64(h*j))
repeatedGophersImage.DrawImage(gophersImage, op)
}
}
}
func init() {
const fogHeight = 8
fogRGBA := image.NewRGBA(image.Rect(0, 0, groundWidth, fogHeight))
for j := 0; j < fogHeight; j++ {
a := uint32(float64(fogHeight-1-j) * 0xff / (fogHeight - 1))
clr := skyColor
r, g, b, oa := uint32(clr.R), uint32(clr.G), uint32(clr.B), uint32(clr.A)
clr.R = uint8(r * a / oa)
clr.G = uint8(g * a / oa)
clr.B = uint8(b * a / oa)
clr.A = uint8(a)
for i := 0; i < groundWidth; i++ {
fogRGBA.SetRGBA(i, j, clr)
}
}
fogImage, _ = ebiten.NewImageFromImage(fogRGBA, ebiten.FilterNearest)
}
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type player struct {
x16 int
y16 int
angle int
lean int
}
func round(x float64) float64 {
return math.Floor(x + 0.5)
}
func (p *player) MoveForward() {
w, h := gophersImage.Size()
mx := w * 16
my := h * 16
s, c := math.Sincos(float64(p.angle) * 2 * math.Pi / maxAngle)
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p.x16 += int(round(16*c) * 2)
p.y16 += int(round(16*s) * 2)
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for mx <= p.x16 {
p.x16 -= mx
}
for my <= p.y16 {
p.y16 -= my
}
for p.x16 < 0 {
p.x16 += mx
}
for p.y16 < 0 {
p.y16 += my
}
}
func (p *player) RotateRight() {
p.angle++
if maxAngle <= p.angle {
p.angle -= maxAngle
}
p.lean++
if maxLean < p.lean {
p.lean = maxLean
}
}
func (p *player) RotateLeft() {
p.angle--
if p.angle < 0 {
p.angle += maxAngle
}
p.lean--
if p.lean < -maxLean {
p.lean = -maxLean
}
}
func (p *player) Stabilize() {
if 0 < p.lean {
p.lean--
}
if p.lean < 0 {
p.lean++
}
}
func (p *player) Position() (int, int) {
return p.x16, p.y16
}
func (p *player) Angle() int {
return p.angle
}
func updateGroundImage(ground *ebiten.Image) {
ground.Clear()
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x16, y16 := thePlayer.Position()
a := thePlayer.Angle()
gw, gh := ground.Size()
w, h := gophersImage.Size()
op := &ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(-x16)/16, float64(-y16)/16)
op.GeoM.Translate(float64(-w*2), float64(-h*2))
op.GeoM.Rotate(float64(-a)*2*math.Pi/maxAngle + math.Pi*3.0/2.0)
op.GeoM.Translate(float64(gw)/2, float64(gh)-32)
ground.DrawImage(repeatedGophersImage, op)
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}
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// scaleForLine calculates the scale to render at y-th line of the ground image.
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func scaleForLine(y int) float64 {
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// c |
// |\ |
// | \|
// | s
// | |\
// | | \
// A--B--C (plane)
//
// c: camera
// s: intersection of the ray and the screen
// B-s: horizon height
// A-C: far point on the plane
// A-B: the distance from the camera to the screen
//
// The ground image is on the plane, and the head of the ground image is on 'C'.
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const (
horizonHeight = screenHeight * 2.0 / 3.0
cameraHeight = horizonHeight + 200.0
farPointOnPlane = 200.0
cameraToScreen = farPointOnPlane - farPointOnPlane/cameraHeight*horizonHeight
)
s1 := cameraHeight / (farPointOnPlane - float64(y)) * (farPointOnPlane - float64(y) - cameraToScreen)
s2 := cameraHeight / (farPointOnPlane - float64(y+1)) * (farPointOnPlane - float64(y+1) - cameraToScreen)
if math.IsInf(s1, 0) || math.IsInf(s2, 0) {
return 0
}
return s1 - s2
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}
func drawGroundImage(screen *ebiten.Image, ground *ebiten.Image) {
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w, h := ground.Size()
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g := ebiten.GeoM{}
g.Translate(-float64(w)/2, 0)
g.Rotate(-1 * float64(thePlayer.lean) / maxLean * math.Pi / 8)
g.Translate(float64(w)/2, 0)
g.Translate(float64(screenWidth-w)/2, screenHeight/3)
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op := &ebiten.DrawImageOptions{}
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y := 0.0
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for i := 0; i < h; i++ {
op.GeoM.Reset()
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s := scaleForLine(i)
dx0, dy0 := float64(w)*(1-s)/2, y
op.GeoM.Scale(s, s+1)
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op.GeoM.Translate(float64(dx0), float64(dy0))
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op.GeoM.Concat(g)
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src := image.Rect(0, i, w, i+1)
op.SourceRect = &src
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screen.DrawImage(ground, op)
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y += s
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}
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op = &ebiten.DrawImageOptions{}
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op.GeoM = g
screen.DrawImage(fogImage, op)
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}
func update(screen *ebiten.Image) error {
if ebiten.IsKeyPressed(ebiten.KeySpace) {
thePlayer.MoveForward()
}
rotated := false
if ebiten.IsKeyPressed(ebiten.KeyRight) {
thePlayer.RotateRight()
rotated = true
}
if ebiten.IsKeyPressed(ebiten.KeyLeft) {
thePlayer.RotateLeft()
rotated = true
}
if !rotated {
thePlayer.Stabilize()
}
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if ebiten.IsRunningSlowly() {
return nil
}
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screen.Fill(skyColor)
updateGroundImage(groundImage)
drawGroundImage(screen, groundImage)
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tutrial := "Space: Move forward\nLeft/Right: Rotate"
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msg := fmt.Sprintf("FPS: %0.2f\n%s", ebiten.CurrentFPS(), tutrial)
ebitenutil.DebugPrint(screen, msg)
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return nil
}
func main() {
if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Air Ship (Ebiten Demo)"); err != nil {
log.Fatal(err)
}
}