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examples/airship: Add comments

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This commit is contained in:
Hajime Hoshi 2018-03-12 01:45:15 +09:00
parent bd8a337728
commit 1ff3a0268e
1 changed files with 24 additions and 3 deletions
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21
examples/airship/main.go
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@ -87,10 +87,19 @@ func init() {
fogImage, _ = ebiten.NewImageFromImage(fogRGBA, ebiten.FilterDefault)
}
// player represents the current airship's position.
type player struct {
// x16, y16 represents the position in XY plane in fixed float format.
// The fractional part has 16 bits of precision.
x16 int
y16 int
// angle represents the player's angle in XY plane.
// angle takes an integer value in [0, maxAngle).
angle int
// lean represents the player's leaning.
// lean takes an integer value in [-maxLean, maxLean].
lean int
}
@ -98,6 +107,7 @@ func round(x float64) float64 {
return math.Floor(x + 0.5)
}
// MoveForward moves the player p forward.
func (p *player) MoveForward() {
w, h := gophersImage.Size()
mx := w * 16
@ -119,6 +129,7 @@ func (p *player) MoveForward() {
}
}
// RotateRight rotates the player p in the right direction.
func (p *player) RotateRight() {
p.angle++
if maxAngle <= p.angle {
@ -130,6 +141,7 @@ func (p *player) RotateRight() {
}
}
// RotateLeft rotates the player p in the left direction.
func (p *player) RotateLeft() {
p.angle--
if p.angle < 0 {
@ -141,6 +153,7 @@ func (p *player) RotateLeft() {
}
}
// Stabilize tries to move the player in the stable position (lean).
func (p *player) Stabilize() {
if 0 < p.lean {
p.lean--
@ -150,14 +163,17 @@ func (p *player) Stabilize() {
}
}
// Position returns the player p's position.
func (p *player) Position() (int, int) {
return p.x16, p.y16
}
// Angle returns the player p's angle.
func (p *player) Angle() int {
return p.angle
}
// updateGroundImage updates the ground image according to the current player's position.
func updateGroundImage(ground *ebiten.Image) {
ground.Clear()
@ -173,6 +189,7 @@ func updateGroundImage(ground *ebiten.Image) {
ground.DrawImage(repeatedGophersImage, op)
}
// drawGroundImage draws the ground image to the given screen image.
func drawGroundImage(screen *ebiten.Image, ground *ebiten.Image) {
perspectiveGroundImage.Clear()
gw, _ := ground.Size()
@ -201,6 +218,7 @@ func drawGroundImage(screen *ebiten.Image, ground *ebiten.Image) {
}
func update(screen *ebiten.Image) error {
// Manipulate the player by the input.
if ebiten.IsKeyPressed(ebiten.KeySpace) {
thePlayer.MoveForward()
}
@ -221,9 +239,12 @@ func update(screen *ebiten.Image) error {
return nil
}
// Draw the ground image.
screen.Fill(skyColor)
updateGroundImage(groundImage)
drawGroundImage(screen, groundImage)
// Draw the message.
tutrial := "Space: Move forward\nLeft/Right: Rotate"
msg := fmt.Sprintf("FPS: %0.2f\n%s", ebiten.CurrentFPS(), tutrial)
ebitenutil.DebugPrint(screen, msg)