Draw a sphere: Difference between revisions

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 #include <math.h>
+/* Perlin-like noise.  Still needs more work. */
-typedef double FLOAT;
+double hashed(int *data, int len) {
+#	define rot(a, d) ((a << (d)) | (a >> (32 - d)))
+	unsigned int *d = (void*)data, h = 0x123456, tmp;
+	while (len--) {
-inline FLOAT
+		tmp = *d++;
-rnd(int x) { return ((x^0x5555) * 1103515245) / (FLOAT)(1 << 31); }
+		h += rot(h, 16) ^ (rot(tmp, 5) ^ h);
+	}
+	h ^= rot(h, 7);
-FLOAT nn(int i, int j)
+	h += rot(h, 11);
-{
+	h ^= rot(h, 17);
-	return rnd( (i << (j & 10)) - (j << (i & 5)));
+	h += rot(h, 25);
+#	undef rot
+	return (double)(int)h / (1U << 31);
 }
-FLOAT noise2(FLOAT x, FLOAT y)
+double noise(double x[8], int d)
 {
+#	define sum(s, x) for (s = 0, j = 0; j < d; j++) s += x
-	int i, j;
-	FLOAT u, v, r = 0, r1, r2;
+	int i, j, n[8], o[8], t;
+	double s, scale, ret, w;
+	double u[8], sk[8];
-	i = floor(x), j = floor(y);
+	sum(s, x[j]);
-	u = x - i, v = y - j;
+	scale = 1 / (sqrt(d + 1) + 1);
+	s *= scale;
+	for (i = 0; i < d; i++) {
-#if 1
+		sk[i] = x[i] + s;
-	u = u * u * (3 - 2 * u);
-	v = v * v * (3 - 2 * v);
+		u[i] = sk[i] - (n[i] = floor(sk[i]));
+		o[i] = i;
-#else
+	}
-	u *= u; u *= (1 - u);
-	v *= v; v *= (1 - v);
-#endif
-	r1 = nn(i, j) * (1 - v) + nn(i, j + 1) * v;
-	r2 = nn(i + 1, j) * (1 - v) + nn(i + 1, j + 1) * v;
-	r = r1 * (1 - u) + r2 * u;
+	for (i = 0; i < d - 1; i++)
+		for (j = i; j < d; j++)
+			if (u[o[i]] < u[o[j]])
+				t = o[i], o[i] = o[j], o[j] = t;
+	ret = w = 0;
-	return r;
+	scale /= sqrt(d + 1);
-}
+	for (i = 0; i <= d; i++) {
+		sum(s, n[j]);
+		s *= scale;
+		for (j = 0; j < d; j++) u[j] = x[j] - n[j] + s;
-FLOAT n3(int i, int j, int k)
-{
-	return rnd( (i << ((j + k) & 10)) - (j << ((k + i) & 5)) + (k << ((i + j) & 15)));
-}
+		sum(s, u[j] * u[j]);
+		s = .6 - s;
+		if (s > 0) {
-FLOAT noise3(FLOAT x, FLOAT y, FLOAT z)
+			s *= s;
-{
-	int i, j, k;
+			w += s;
+			ret += hashed(n, d) * s;
-	FLOAT u, v, w, x1, x2, y1, y2;
+		}
+		if (i < d) n[o[i]]++;
-	i = floor(x), j = floor(y), k = floor(z);
+	}
-	u = x - i, v = y - j, w = z - k;
+	return w ? ret / w : 0;
-#if 1
-	u = u * u * (3 - 2 * u);
-	v = v * v * (3 - 2 * v);
-	w = w * w * (3 - 2 * w);
-#else
-	u *= u; u *= (1 - u);
-	v *= v; v *= (1 - v);
-	w *= w; w *= (1 - w);
-#endif
-#define interp(a, b, c) a * (1 - c) + b * c
-	x1 = interp(n3(i, j, k), n3(i + 1, j, k), u);
-	x2 = interp(n3(i, j + 1, k), n3(i + 1, j + 1, k), u);
-	y1 = interp(x1, x2, v);
-	x1 = interp(n3(i, j, k + 1), n3(i + 1, j, k + 1), u);
-	x2 = interp(n3(i, j + 1, k + 1), n3(i + 1, j + 1, k + 1), u);
-	y2 = interp(x1, x2, v);
-	return interp(y1, y2, w);
 }
-FLOAT getnoise2(FLOAT x, FLOAT y)
+double get_noise2(double x, double y)
 {
-	int i;
+	int i, j, ws;
-	FLOAT r = 0, w, s = 0;
+	double r = 0, v[2];
-	for (i = 1; i <= 256; i <<= 1) {
+	for (i = 1, ws = 0; i <= 256; i <<= 1) {
-		w = 1./sqrt(i);
+		v[0] = x * i, v[1] = y * i;
-		s += w;
-		r += noise2(x * i, y * i) * w;
+		r += noise(v, 2);
+		ws ++;
 	}
-	return r / s / 2 + .5;
+	r /= ws;
+	return r;
 }
-FLOAT getnoise(FLOAT x, FLOAT y, FLOAT z)
+double get_noise3(double x, double y, double z)
 {
-	int i;
+	int i, j, ws;
-	FLOAT r = 0, w, s = 0;
+	double r = 0, v[3], w;
-	for (i = 1; i <= 32; i <<= 1) {
+	for (i = 1, ws = 0; i <= 256; i <<= 1) {
-		w = 1./i;
+		v[0] = x * i, v[1] = y * i, v[2] = z * i;
-		s += w;
+		w = 1./sqrt(i);
-		r += (noise3(x * i, y * i, z * i) * w);
+		r += noise(v, 3) * w;
+		ws += w;
 	}
+	return r / ws;
-	r = fmod((r / s + 1) * 2, 1);
-	if (r < .4) return 0;
-	return r;
 }
 int main()
 {
-	unsigned char pix[256 * 256], *p = pix;
+	unsigned char pix[256 * 256], *p;
-	FLOAT fv[256 * 256], *pf = fv;
 	int i, j;
-	FLOAT x, y, z, r;
+	double x, y, z, w;
 	FILE *fp;
-	for (i = 0; i < 256 * 256; i++) *pf++ = 0, *p++ = 0;
+	for (p = pix, i = 0; i < 256 * 256; i++) *p++ = 0;
-	for (i = 0, p = pix; i < 256; i++) {
-		x = (i - 128) / 120.;
+	for (p = pix, i = 0; i < 256; i++) {
+		y = (i - 128) / 125.;
 		for (j = 0; j < 256; j++, p++) {
-			y = (j - 128) / 120.;
+			x = (j - 128) / 125.;
+			*p = (get_noise2(i/256., j/256.) + 1) / 6 * i * i / 256;
-			*p = i * getnoise2(x, y);
+			z = 1- x*x - y*y;
+			if (z < 0) continue;
-			z = 1 - x*x - y*y;
-			if (z < 0) { continue; }
 			z = sqrt(z);
-			r = getnoise(x, y, -z);
+			w = get_noise3(x, y, z) / 2 + .5;
-			if (r) *p = 50;
-			r = getnoise(x, y, z);
+			w = w * (x + y + z) / 2.2;
-			if (r) {
+			if (w < 0) w = 0;
-				r = (x + y + z) / 2.3 + .5;
+			*p = w * 255;
-				if (r > 1) r = 1;
-				*p = 180 * r + 70;
-			}
 		}
 	}