From 847f72f9be868fdef8fad85aea64636a0491a0f2 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sun, 17 Jul 2016 05:36:06 +0900
Subject: [PATCH] Add examples/airship (#246)

---
 examples/airship/main.go | 218 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 218 insertions(+)
 create mode 100644 examples/airship/main.go

diff --git a/examples/airship/main.go b/examples/airship/main.go
new file mode 100644
index 000000000..5eecf70ad
--- /dev/null
+++ b/examples/airship/main.go
@@ -0,0 +1,218 @@
+// 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.
+
+package main
+
+import (
+	"fmt"
+	"image/color"
+	"log"
+	"math"
+
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+	"github.com/hajimehoshi/ebiten/examples/common"
+)
+
+const (
+	screenWidth  = 320
+	screenHeight = 240
+	maxAngle     = 256
+	maxLean      = 16
+)
+
+var (
+	skyColor     = color.RGBA{0x66, 0xcc, 0xff, 0xff}
+	thePlayer    = &player{}
+	gophersImage *ebiten.Image
+	groundImage  *ebiten.Image
+)
+
+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)
+	p.x16 += int(round(16 * c))
+	p.y16 += int(round(16 * s))
+	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) error {
+	if err := ground.Clear(); err != nil {
+		return nil
+	}
+	x16, y16 := thePlayer.Position()
+	a := thePlayer.Angle()
+	gw, gh := ground.Size()
+	w, h := gophersImage.Size()
+	for j := -1; j <= 1; j++ {
+		for i := -1; i <= 1; i++ {
+			op := &ebiten.DrawImageOptions{}
+			op.GeoM.Translate(float64(-x16)/16, float64(-y16)/16)
+			op.GeoM.Translate(float64(w*i), float64(h*j))
+			op.GeoM.Rotate(float64(-a)*2*math.Pi/maxAngle + math.Pi*3.0/2.0)
+			op.GeoM.Translate(float64(gw)/2, float64(gh))
+			if err := ground.DrawImage(gophersImage, op); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+type groundParts struct {
+	image *ebiten.Image
+}
+
+func (g *groundParts) Len() int {
+	_, h := g.image.Size()
+	return h
+}
+
+func (g *groundParts) Src(i int) (int, int, int, int) {
+	w, _ := g.image.Size()
+	r := 60 - (i+10)/4
+	return w/2 - r, i, w/2 + r, i + 1
+}
+
+func (g *groundParts) Dst(i int) (int, int, int, int) {
+	w, _ := g.image.Size()
+	return 0, i, w, i + 1
+}
+
+func drawGroundImage(screen *ebiten.Image, ground *ebiten.Image) error {
+	w, _ := ground.Size()
+	op := &ebiten.DrawImageOptions{}
+	op.GeoM.Translate(-float64(w)/2, 0)
+	op.GeoM.Rotate(-1 * float64(thePlayer.lean) / maxLean * math.Pi / 8)
+	op.GeoM.Translate(float64(w)/2, 0)
+	op.GeoM.Translate(float64(screenWidth-w)/2, screenHeight/2)
+	op.ImageParts = &groundParts{ground}
+	if err := screen.DrawImage(ground, op); err != nil {
+		return err
+	}
+	return nil
+}
+
+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()
+	}
+
+	if err := screen.Fill(skyColor); err != nil {
+		return err
+	}
+	if err := updateGroundImage(groundImage); err != nil {
+		return err
+	}
+	if err := drawGroundImage(screen, groundImage); err != nil {
+		return err
+	}
+
+	tutrial := "Space: Move foward\nLeft/Right: Rotate"
+	msg := fmt.Sprintf("FPS: %0.2f\n%s", ebiten.CurrentFPS(), tutrial)
+	if err := ebitenutil.DebugPrint(screen, msg); err != nil {
+		return err
+	}
+	return nil
+}
+
+func main() {
+	var err error
+	gophersImage, _, err = common.AssetImage("gophers.jpg", ebiten.FilterNearest)
+	if err != nil {
+		log.Fatal(err)
+	}
+	groundImage, err = ebiten.NewImage(screenWidth+70, screenHeight/2+50, ebiten.FilterNearest)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Air Ship (Ebiten Demo)"); err != nil {
+		log.Fatal(err)
+	}
+}