func (c *Critter) initAlienVelocity() { // Choose random velocity // This peculiar 2D distibution was in the original sources. // It was probably an error, but is now traditional in Frequon Invaders. // It biases towards diagonal directions c.vx = math32.Cos(2*π*rand.Float32()) * velocityMax c.vy = math32.Sin(2*π*rand.Float32()) * velocityMax }
func init() { Twang = makeSound(44100, func(i float32) float32 { const ω = 110 * 2 * π / nimble.SampleRate const nharmonic = 32 sum := float32(0) for h := float32(1); h <= nharmonic; h++ { sum += math32.Sin(ω*h*i) * math32.Exp(-i*0.00004*h) } return sum / nharmonic }) n := len(Twang) AntiTwang = make([]float32, n) for i := range AntiTwang { AntiTwang[i] = Twang[n-1-i] } sum := float32(0) Broken = makeSound(44100, func(i float32) float32 { r := (rand.Float32() - 0.5) * (1.0 / 16) newSum := sum + r if math32.Abs(newSum) < 1.0 { sum = newSum } sum *= (1 - 1/32.0) return sum * math32.Exp(-i*.0001) }) Wobble = makeSound(44100, func(i float32) float32 { return 0.25 * math32.Sin((440+44*math32.Sin(i*0.001))*i*(2*π/nimble.SampleRate)) * math32.Exp(-i*0.00005) }) partials := [...]float32{0.56, 0.92, 1.19, 1.71, 2.00, 2.74, 3.00, 3.76, 4.07} Bell = makeSound(44100, func(i float32) float32 { const θ = 512 * 2 * π / nimble.SampleRate sum := float32(0) const n = float32(len(partials)) for j := range partials { sum += math32.Sin(i * θ * partials[j]) } return sum * (1.0 / n) * math32.Exp(-i*0.0001) }) }