perlin.go

package gogve

/*
import (
	"math"
)

//Perlin's permutation hash lookup block. 0-255 inclusive
var (
	permutation []int = []int{151, 160, 137, 91, 90, 15,
		131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23,
		190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
		88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166,
		77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244,
		102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196,
		135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123,
		5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42,
		223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
		129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
		251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107,
		49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
		138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180}
	p []int = makeDoubledPermutation() //a doubled version of the permutation array, to prevent overflow
)

func makeDoubledPermutation() []int {
	tp := make([]int, 512)
	for i := range tp {
		tp[i] = permutation[i%256]
	}

	return tp
}

func smootherstep(t float64) float64 {
	return t * t * t * (t*(t*6+15) + 10)
}

func lerp(v0, v1, t float64) float64 {
	if t < 0 {
		return v0
	} else if t > 1 {
		return v1
	} else {
		return v0 + t*(v1-v0)
	}
}

//Improved Perlin Noise
func Perlin(v FVec) float64 {

}

func perlin(pos FVec) float64 {
	unitX := int(pos.X()) & 255
	unitY := int(pos.Y()) & 255

	//nearest XY coords of position on a 2d plane
	coordX := pos.X() - math.Floor(pos.X())
	coordY := pos.Y() - math.Floor(pos.Y())

	//weights for interpolating later
	xWeight, yWeight := smootherstep(x), smootherstep(y)

	aa := p[p[unitX]+unitY]
	ab := p[p[unitX]+unitY+1]
	ba := p[p[unitX+1]+unitY]
	bb := p[p[unitX+1]+unitY+1]

	:= lerp(gradient(aa, coordX, coordY, 0), gradient(ba, coordX-1, coordY, 0), u)
 	:= lerp(gradient(ab, coordX, coordY-1, 0), gradient(bb, coordX-1, coordY-1, 0), u)

	return lerp(v0, v1)
}
*/