98 lines
3 KiB
Forth
98 lines
3 KiB
Forth
PROGRAM PERLIN
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IMPLICIT NONE
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INTEGER :: i
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INTEGER, DIMENSION(0:511) :: p
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INTEGER, DIMENSION(0:255), PARAMETER :: permutation = (/151,160,137,91,90,15, &
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131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23, &
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190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33, &
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88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166, &
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77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244, &
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102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196, &
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135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123, &
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5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42, &
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223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9, &
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129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228, &
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251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107, &
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49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254, &
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138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180/)
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DO i=0, 255
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p(i) = permutation(i)
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p(256+i) = permutation(i)
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END DO
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WRITE(*,"(F19.17)") NOISE(3.14d0, 42d0, 7d0)
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CONTAINS
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DOUBLE PRECISION FUNCTION NOISE(x_in, y_in, z_in)
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DOUBLE PRECISION, INTENT(IN) :: x_in, y_in, z_in
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DOUBLE PRECISION :: x, y, z
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INTEGER :: xx, yy, zz, a, aa, ab, b, ba, bb
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DOUBLE PRECISION :: u, v, w
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x = x_in
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y = y_in
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z = z_in
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xx = IAND(FLOOR(x), 255)
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yy = IAND(FLOOR(y), 255)
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zz = IAND(FLOOR(z), 255)
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x = x - FLOOR(x)
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y = y - FLOOR(y)
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z = z - FLOOR(z)
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u = FADE(x)
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v = FADE(y)
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w = FADE(z)
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a = p(xx) + yy
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aa = p(a) + zz
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ab = p(a+1) + zz
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b = p(xx+1) + yy
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ba = p(b) + zz
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bb = p(b+1) + zz
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NOISE = LERP(w, LERP(v, LERP(u, GRAD(p(aa), x, y, z), &
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GRAD(p(ba), x-1, y, z)), &
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LERP(u, GRAD(p(ab), x, y-1, z), &
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GRAD(p(bb), x-1, y-1, z))), &
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LERP(v, LERP(u, GRAD(p(aa+1), x, y, z-1), &
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GRAD(p(ba+1), x-1, y, z-1)), &
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LERP(u, GRAD(p(ab+1), x, y-1, z-1), &
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GRAD(p(bb+1), x-1, y-1, z-1))))
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END FUNCTION
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DOUBLE PRECISION FUNCTION FADE(t)
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DOUBLE PRECISION, INTENT(IN) :: t
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FADE = t ** 3 * (t * ( t * 6 - 15) + 10)
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END FUNCTION
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DOUBLE PRECISION FUNCTION LERP(t, a, b)
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DOUBLE PRECISION, INTENT(IN) :: t, a, b
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LERP = a + t * (b - a)
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END FUNCTION
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DOUBLE PRECISION FUNCTION GRAD(hash, x, y, z)
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INTEGER, INTENT(IN) :: hash
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DOUBLE PRECISION, INTENT(IN) :: x, y, z
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INTEGER :: h
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DOUBLE PRECISION :: u, v
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h = IAND(hash, 15)
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u = MERGE(x, y, h < 8)
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v = MERGE(y, MERGE(x, z, h == 12 .OR. h == 14), h < 4)
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GRAD = MERGE(u, -u, IAND(h, 1) == 0) + MERGE(v, -v, IAND(h, 2) == 0)
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END FUNCTION
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END PROGRAM
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