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commit adb5d714d9510104e9abb3b4de34ab409fd26a6b
parent 0a7ea95bd8c25187b82517c8db5dedef6275f04b
Author: Georges Dupéron <jahvascriptmaniac+github@free.fr>
Date:   Sun,  2 Oct 2011 12:17:31 +0200

Petite optimisation de la fonction de hachage.

Diffstat:
M
display.c
 | 
4
++--
M
roam.c
 | 
39
+++++----------------------------------

2 files changed, 7 insertions(+), 36 deletions(-)
diff --git a/display.c b/display.c
@@ -102,12 +102,12 @@ int main() {
 	// Pour afficher le terrain :
 	/* int x; */
 	/* int y; */
-	/* #define SIZE 256 */
+	/* #define SIZE 1024 */
 	/* printf("P5 %d %d 255\n", SIZE, SIZE); */
 	/* for (y = 0; y < SIZE; y++) { */
 	/* 	for (x = 0; x < SIZE; x++) { */
 	/* 		//int bit = y / (SIZE/32); */
-	/* 		//int h = hash2(t,hash2(x, y)); */
+	/* 		//int h = hash2(x, 300+y); */
 	/* 		//if (y % (SIZE/32) == 0) h = 0; */
 	/* 		//printf("%c", ((h >> (31-bit)) & 1) * 255); */
 	/* 		//printf("%c", interpolation(256+x, 256+y, 256, 256, 512, 512, 0, 255, 255, 255)); */
diff --git a/roam.c b/roam.c
@@ -41,23 +41,17 @@ int getFirstTriangleSize(Triangle* t) {
 	return sqrt(((t->vRight->x - t->vLeft->x)^2) + ((t->vRight->y - t->vLeft->y)^2));
 }
 
-// TODO : à supprimer.
-unsigned int getValueForSeed(unsigned int seed) {
-	unsigned int primeA = 65521; // Plus grand premier < 2^16
-	unsigned int primeB = 4294967291U; // Plus grand premier < 2^32
-	return ((seed * primeA) ^ ((seed+1) * primeB)) + seed; // + seed pour éviter d'avoir uniquement des nombres impairs.
-}
-
 // Ce hash donne des bons résultats sur tous les bits de l'entier
 // généré (pas d'artefacts, répartition homogène des 0 et des 1).
 unsigned int hash2(unsigned int a, unsigned int b) {
 	unsigned int h = 1;
 	int i;
 	for (i = 0; i < 32; i+=8) {
-		a *= h;
-		b *= h;
-		h = h * 65599 + ((a >> i) & 0xff);
-		h = h * 65599 + ((b >> i) & 0xff);
+		a = a*h + 1;
+		b = b*h + 1;
+		// marche aussi avec 65521.
+		h = (h << 6) + (h << 16) - h + ((a >> i) & 0xff); // h * 65599 + ieme octet de a
+		h = (h << 6) + (h << 16) - h + ((b >> i) & 0xff); // h * 65599 + ieme octet de b
 	}
 	return h;
 }
@@ -83,29 +77,6 @@ int interpolation(int x, int y, int x1, int y1, int x2, int y2, int ne, int se, 
 	return ret / ((x2-x1) * (y2-y1));
 }
 
-short** PerlinNoise(Triangle* t) {
-	short **values;
-	int triangleSize = getFirstTriangleSize(t);
-	int i;
-	int seed;
-	int x,y;
-	
-	seed = (int)(t->vApex->x / triangleSize + t->vApex->y / triangleSize)*1111;
-	
-	values = (short**) malloc(sizeof(short*)*triangleSize);
-	for(i=0; i<triangleSize;i++)
-		values[i] = (short*) malloc(sizeof(short)*triangleSize);
-	
-	for(i=0; i<8;i++) {
-		x = getValueForSeed(seed);
-		y = getValueForSeed(x);
-		values[x][y] = 255;
-	}
-	
-	// TODO Yoann : tout le reste.
-	return values;
-}
-
 // renvoie un z entre 0 et 255
 int get_z(int x, int y) {
 	x = x; /* Unused */