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example/airship: Add comments

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This commit is contained in:
Hajime Hoshi 2018-01-22 00:20:35 +09:00
parent a0ad4710f7
commit 3ee42c0c1e
1 changed files with 18 additions and 0 deletions
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18
examples/airship/main.go
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@ -56,6 +56,7 @@ func init() {
panic(err)
}
groundImage, _ = ebiten.NewImage(groundWidth, screenHeight*2/3+50, ebiten.FilterNearest)
const repeat = 5
w, h := gophersImage.Size()
repeatedGophersImage, _ = ebiten.NewImage(w*repeat, h*repeat, ebiten.FilterNearest)
@ -159,6 +160,7 @@ func (p *player) Angle() int {
func updateGroundImage(ground *ebiten.Image) {
ground.Clear()
x16, y16 := thePlayer.Position()
a := thePlayer.Angle()
gw, gh := ground.Size()
@ -171,7 +173,23 @@ func updateGroundImage(ground *ebiten.Image) {
ground.DrawImage(repeatedGophersImage, op)
}
// scaleForLine calculates the scale to render at y-th line of the ground image.
func scaleForLine(y int) float64 {
// 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'.
const (
horizonHeight = screenHeight * 2.0 / 3.0
cameraHeight = horizonHeight + 200.0