16867578561

Committed 10 Aug 2025 11:29PM UTC coverage: 94.565% (-5.4%) from 100.0%

Build # 16867578561

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push

github

Committed by

web-flow

Commit Message

Merge pull request #3 from kelindar/grads

Refactor noise computation and update benchmark results in README

Coverage Stats

20 of 20 new or added lines in 1 file covered. (100.0%)

5 existing lines in 1 file now uncovered.

87 of 92 relevant lines covered (94.57%)

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94.57

/simplex.go

1	package simplex
2
3	const (
4	f2 = 0.36602542 // float32(0.5 * (math.Sqrt(3) - 1))
5	g2 = 0.21132487 // float32((3 - math.Sqrt(3)) / 6)
6	)
7
8	var (
9	perm [512]uint8
10	grad [512][2]float32
11	)
12
13	var table = []uint8{151, 160, 137, 91, 90, 15,
14	131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23,
15	190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
16	88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166,
17	77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244,
18	102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196,
19	135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123,
20	5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42,
21	223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
22	129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
23	251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107,
24	49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
25	138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180}
26
27	func init() {	1✔
28	var g2d = [12]uint16{	1✔
29	0x0101, // [+1, +1]	1✔
30	0xff01, // [-1, +1]	1✔
31	0x01ff, // [+1, -1]	1✔
32	0xffff, // [-1, -1]	1✔
33	0x0100, // [+1, +0]	1✔
34	0xff00, // [-1, +0]	1✔
35	0x0100, // [+1, +0]	1✔
36	0xff00, // [-1, +0]	1✔
37	0x0001, // [+0, +1]	1✔
38	0x00ff, // [+0, -1]	1✔
39	0x0001, // [+0, +1]	1✔
40	0x00ff, // [+0, -1]	1✔
41	}	1✔
42		1✔
43	for i := 0; i < 512; i++ {	513✔
44	perm[i] = table[i&255]	512✔
45	idx := g2d[perm[i]%12]	512✔
46	gx := int8(idx >> 8)	512✔
47	gy := int8(idx)	512✔
48	grad[i] = [2]float32{float32(gx), float32(gy)}	512✔
49	}	512✔
50	}
51
52	// Noise2 computes a two dimensional simplex noise
53	// Public Domain: https://weber.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
54	// Reference: https://mrl.cs.nyu.edu/~perlin/noise/
55	func Noise2(x, y float32) float32 {	250,000✔
56		250,000✔
57	// Skew the input space to determine which simplex cell we're in	250,000✔
58	s := (x + y) * f2	250,000✔
59	i := floor(x + s)	250,000✔
60	j := floor(y + s)	250,000✔
61		250,000✔
62	// Unskew the cell origin back to (x,y) space	250,000✔
63	t := float32(i+j) * g2	250,000✔
64	x0 := x - (float32(i) - t)	250,000✔
65	y0 := y - (float32(j) - t)	250,000✔
66		250,000✔
67	// For the 2D case, the simplex shape is an equilateral triangle.	250,000✔
68	// Determine which simplex we are in	250,000✔
69	i1, j1 := float32(0), float32(1) // upper triangle	250,000✔
70	if x0 > y0 { // lower triangle	372,893✔
71	i1 = 1	122,893✔
72	j1 = 0	122,893✔
73	}	122,893✔
74
75	// Offsets for middle corner in (x,y) unskewed coords
76	x1 := x0 - i1 + g2	250,000✔
77	y1 := y0 - j1 + g2	250,000✔
78		250,000✔
79	// Offsets for middle corner in (x,y) unskewed coords	250,000✔
80	const g = 2 * g2	250,000✔
81	x2 := x0 - 1 + g	250,000✔
82	y2 := y0 - 1 + g	250,000✔
83		250,000✔
84	// Work out the hashed gradient indices of the three simplex corners	250,000✔
85	ii := int(i & 255)	250,000✔
86	jj := int(j & 255)	250,000✔
87		250,000✔
88	// Use slice windows	250,000✔
89	pp := perm[jj:]	250,000✔
90	gg := grad[ii:]	250,000✔
91	p0 := int(pp[0])	250,000✔
92	p1 := int(pp[int(j1)])	250,000✔
93	p2 := int(pp[1])	250,000✔
94	g0 := gg[p0]	250,000✔
95	g1 := gg[int(i1)+p1]	250,000✔
96	g2 := gg[1+p2]	250,000✔
97		250,000✔
98	// Calculate the contribution from the three corners	250,000✔
99	n := float32(0.0)	250,000✔
100	if t := 0.5 - x0x0 - y0y0; t > 0 {	476,854✔
101	n += pow4(t) * (g0[0]x0 + g0[1]y0)	226,854✔
102	}	226,854✔
103	if t := 0.5 - x1x1 - y1y1; t > 0 {	474,558✔
104	n += pow4(t) * (g1[0]x1 + g1[1]y1)	224,558✔
105	}	224,558✔
106	if t := 0.5 - x2x2 - y2y2; t > 0 {	476,730✔
107	n += pow4(t) * (g2[0]x2 + g2[1]y2)	226,730✔
108	}	226,730✔
109
110	// Add contributions from each corner to get the final noise value.
111	// The result is scaled to return values in the interval [-1,1].
112	return 70.0 * n	250,000✔
113	}
114
115	// pow4 lifts the value to the power of 4
116	func pow4(v float32) float32 {	678,142✔
117	v *= v	678,142✔
118	v *= v	678,142✔
119	return v	678,142✔
120	}	678,142✔
121
122	// dot2D computes dot product with the gradient
UNCOV 123	func dot2D(g uint16, x, y float32) float32 {	×
UNCOV 124	gx := float32(int8(g >> 8))	×
UNCOV 125	gy := float32(int8(g))	×
UNCOV 126	return gxx + gyy	×
UNCOV 127	}	×
128
129	// floor floors the floating-point value to an integer
130	func floor(x float32) int {	500,003✔
131	v := int(x)	500,003✔
132	if x < float32(v) {	500,004✔
133	return v - 1	1✔
134	}	1✔
135	return v	500,002✔
136	}

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