Mercurial > hg > dmlib
view dmperlin.c @ 510:43ea59887c69
Start work on making C64 formats encoding possible by changing DMDecodeOps
to DMEncDecOps and adding fields and op enums for custom encode functions, renaming,
etc. Split generic op sanity checking into a separate function in
preparation for its use in generic encoding function.
author | Matti Hamalainen <ccr@tnsp.org> |
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date | Mon, 19 Nov 2012 15:06:01 +0200 |
parents | 32250b436bca |
children | 62f5861d332b |
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/* * Coherent noise function over 1 or 2 dimensions. */ #include "dmlib.h" #include <math.h> #define B (0x100) #define BM (0x0ff) #define NP (12) #define N (0x1000) #define NM (0x0fff) #define DM_PERLIN_SETUP(i, b0, b1, r0, r1) { \ t = (vec[i] + N); \ b0 = (((int) t) & BM); \ b1 = ((b0 + 1) & BM); \ r0 = (t - ((int) t)); \ r1 = (r0 - 1.0f); \ } #define DM_PERLIN_AT2(rx,ry) ((rx) * q[0] + (ry) * q[1]) static int p[B + B + 2]; static DMFloat g2[B + B + 2][2]; static DMFloat g1[B + B + 2]; static DMFloat dmPerlinDoNoise2(DMFloat vec[2]) { int bx0, bx1, by0, by1, b00, b10, b01, b11; DMFloat rx0, rx1, ry0, ry1, *q, sx, sy, a, b, t, u, v; int i, j; DM_PERLIN_SETUP(0, bx0, bx1, rx0, rx1); DM_PERLIN_SETUP(1, by0, by1, ry0, ry1); i = p[bx0]; j = p[bx1]; b00 = p[i + by0]; b10 = p[j + by0]; b01 = p[i + by1]; b11 = p[j + by1]; sx = DMM_S_CURVE(rx0); sy = DMM_S_CURVE(ry0); q = g2[b00]; u = DM_PERLIN_AT2(rx0, ry0); q = g2[b10]; v = DM_PERLIN_AT2(rx1, ry0); a = DMM_LERP(sx, u, v); q = g2[b01]; u = DM_PERLIN_AT2(rx0, ry1); q = g2[b11]; v = DM_PERLIN_AT2(rx1, ry1); b = DMM_LERP(sx, u, v); return DMM_LERP(sy, a, b); } static void dmPerlinNormalize2(DMFloat v[2]) { DMFloat s; s = sqrt(v[0] * v[0] + v[1] * v[1]); v[0] /= s; v[1] /= s; } void dmPerlinInit(void) { int i, j, k; srand(32); for (i = 0; i < B; i++) { p[i] = i; g1[i] = (DMFloat) ((rand() % (B + B)) - B) / B; for (j = 0; j < 2; j++) g2[i][j] = (DMFloat) ((rand() % (B + B)) - B) / B; dmPerlinNormalize2(g2[i]); } while (--i) { k = p[i]; p[i] = p[j = rand() % B]; p[j] = k; } for (i = 0; i < B + 2; i++) { p[B + i] = p[i]; g1[B + i] = g1[i]; for (j = 0; j < 2; j++) g2[B + i][j] = g2[i][j]; } } /* Harmonic summing functions - PDB * In what follows "alpha" is the weight when the sum is formed. * Typically it is 2, As this approaches 1 the function is noisier. * "beta" is the harmonic scaling/spacing, typically 2. */ DMFloat dmPerlinNoise2D(DMFloat x, DMFloat y, DMFloat alpha, DMFloat beta, int n) { int i; DMFloat val, sum = 0; DMFloat p[2], scale = 1; p[0] = x; p[1] = y; for (i = 0; i < n; i++) { val = dmPerlinDoNoise2(p); sum += val / scale; scale *= alpha; p[0] *= beta; p[1] *= beta; } return (sum); }