38 lines
1.3 KiB
D
38 lines
1.3 KiB
D
void main() {
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import core.stdc.stdio, std.random, grayscale_image;
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enum uint side = 600; // Square world side.
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enum uint num_particles = 10_000;
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static assert(side > 2 && num_particles < (side ^^ 2 * 0.7));
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auto rng = unpredictableSeed.Xorshift;
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ubyte[side][side] W; // World.
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W[side / 2][side / 2] = 1; // Set tree root.
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foreach (immutable _; 0 .. num_particles) {
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// Random initial particle position.
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OVER: uint x, y;
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do {
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x = uniform(1, side - 1, rng);
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y = uniform(1, side - 1, rng);
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} while (W[y][x]); // Assure the chosen cell is empty.
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while (W[y-1][x-1] + W[y-1][x] + W[y-1][x+1] +
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W[y][x-1] + W[y][x+1] +
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W[y+1][x-1] + W[y+1][x] + W[y+1][x+1] == 0) {
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// Randomly choose a direction (Moore neighborhood).
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uint dxy = uniform(0, 8, rng);
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if (dxy > 3) dxy++; // To avoid the center.
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x += (dxy % 3) - 1;
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y += (dxy / 3) - 1;
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if (x < 1 || x >= side - 1 || y < 1 || y >= side - 1)
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goto OVER;
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}
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W[y][x] = 1; // Touched, set the cell.
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}
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ubyte[] data = (&W[0][0])[0 .. side ^^ 2]; // Flat view.
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data[] += 255;
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Image!ubyte.fromData(data, side, side).savePGM("brownian_tree.pgm");
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}
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