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examples/airship: Better line scaling

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This commit is contained in:
Hajime Hoshi 2018-01-21 23:51:56 +09:00
parent a6a1c51df7
commit a0ad4710f7
1 changed files with 21 additions and 9 deletions
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30
examples/airship/main.go
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@ -171,9 +171,19 @@ func updateGroundImage(ground *ebiten.Image) {
ground.DrawImage(repeatedGophersImage, op)
}
func scaleForLine(x int) float64 {
// This is an very rough approximate calculation.
return math.Pow(float64(x)/2.5, 1.2)
func scaleForLine(y int) float64 {
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
}
func drawGroundImage(screen *ebiten.Image, ground *ebiten.Image) {
@ -184,20 +194,20 @@ func drawGroundImage(screen *ebiten.Image, ground *ebiten.Image) {
g.Translate(float64(w)/2, 0)
g.Translate(float64(screenWidth-w)/2, screenHeight/3)
op := &ebiten.DrawImageOptions{}
y := 0.0
for i := 0; i < h; i++ {
op.GeoM.Reset()
x := scaleForLine(i)
j := scaleForLine(i)
dx0, dy0, dx1, dy1 := -x, j, float64(w)+x, j+6
sw := float64(dx1-dx0) / float64(w)
sh := float64(dy1 - dy0)
op.GeoM.Scale(sw, sh)
s := scaleForLine(i)
dx0, dy0 := float64(w)*(1-s)/2, y
op.GeoM.Scale(s, s+1)
op.GeoM.Translate(float64(dx0), float64(dy0))
op.GeoM.Concat(g)
src := image.Rect(0, i, w, i+1)
op.SourceRect = &src
screen.DrawImage(ground, op)
y += s
}
op = &ebiten.DrawImageOptions{}
op.GeoM = g
@ -220,9 +230,11 @@ func update(screen *ebiten.Image) error {
if !rotated {
thePlayer.Stabilize()
}
if ebiten.IsRunningSlowly() {
return nil
}
screen.Fill(skyColor)
updateGroundImage(groundImage)
drawGroundImage(screen, groundImage)