2d perlin noise used for procedural terrain

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2D Perlin noise is a gradient noise function commonly used in computer graphics and procedural generation. It generates a smooth, continuous, and random-looking pattern in two dimensions.

Overall, 2D Perlin noise is widely used in game development and other graphical applications for generating realistic textures and natural patterns

-- Original permutation table
sequence base_permutation

base_permutation= {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}
                           
                           

-- Function to shuffle the permutation table
function shuffle(sequence perm)
    integer n,j,temp
    n= length(perm)
    for i = n to 2 by -1 do
         j = rand(i)
        -- Swap elements
         temp = perm[i]
        perm[i] = perm[j]
        perm[j] = temp
    end for
    return perm
end function

-- Seed the random number generator with the current time

set_rand(get_tick_count())

-- Create a shuffled permutation table
sequence permutation
permutation = shuffle(base_permutation)

-- Double the permutation table to avoid overflow when indexing
permutation &= permutation

-- Helper function for modulo operation in Euphoria 3.1
function mod(integer a, integer b)
    return a - b * floor(a / b)  +1
end function

-- Function to generate gradient vectors based on the permutation table
function gradient(integer hash)
    atom angle
    angle= 2 * PI * hash / 256.0
    return {cos(angle), sin(angle)}
end function

-- Linear interpolation function
function lerp(atom a, atom b, atom t)
    return a + t * (b - a)
end function

-- Fade function to smooth out the interpolation
function fade(atom t)
    return t * t * t * (t * (t * 6 - 15) + 10)
end function

-- Dot product of the gradient vector and the distance vector
function dot_grid_gradient(integer ix, integer iy, atom x, atom y)
    atom dx, dy
    sequence g
    integer hash
    -- Use permutation table to get a gradient hash
    hash= permutation[mod(permutation[mod(ix, 256)] + iy, 256)]
    g = gradient(hash)

    -- Calculate the distance from the grid point
    dx = x - ix
    dy = y - iy

    -- Return the dot product of the gradient and distance vectors
    return dx * g[1] + dy * g[2]
end function

-- Main 2D Perlin noise function
global function perlin(atom x, atom y)
    integer x0, x1, y0, y1
    atom sx, sy, n0, n1, ix0, ix1

    -- Determine grid cell coordinates
    x0 = floor(x)
    x1 = x0 + 1
    y0 = floor(y)
    y1 = y0 + 1

    -- Calculate interpolation weights
    sx = fade(x - x0)
    sy = fade(y - y0)

    -- Calculate noise contributions from the four corners
    n0 = dot_grid_gradient(x0, y0, x, y)
    n1 = dot_grid_gradient(x1, y0, x, y)
    ix0 = lerp(n0, n1, sx)

    n0 = dot_grid_gradient(x0, y1, x, y)
    n1 = dot_grid_gradient(x1, y1, x, y)
    ix1 = lerp(n0, n1, sx)

    -- Interpolate the final value
    return lerp(ix0, ix1, sy)
end function

-- Example usage: generating noise for a 10x10 grid
constant size = 10
for y = 0 to size - 1 do
    for x = 0 to size - 1 do
        printf(1, "%.2f ", {perlin(x * 0.1, y * 0.1)})
    end for
    puts(1, "\n")
end for

 

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