c - Minecraft Flood fill -


i trying calculate minecraft's light values, algorithm use slow.

what better way calculate lighting array?

the code looks this:

struct chunk_data {     char light[16*16*256]; };  int j;  void fill(chunk_data* c, int i, int l) {         ++j;         if(c->light[i] > l)                 return;         c->light[i] = l;         if(!--l)                 return;         if((i&0x0f) != 0x0f)                 fill(c, + 0x01, l);         if((i&0x0f) != 0x00)                 fill(c, - 0x01, l);         if((i&0xf0) != 0xf0)                 fill(c, + 0x10, l);         if((i&0xf0) != 0x00)                 fill(c, - 0x10, l);         if((i&0xff00) != 0x0000)                 fill(c, - 0x0100, l);         if((i&0xff00) != 0xff00)                 fill(c, + 0x0100, l); }

when move check before call recursion, number of stack pushes reduced. reduces running time 250ms 23us.

improved code:

void fill(chunk_data* c, int i, int l) {         c->light[i] = l;         if(!--l)                 return;         if((i&0x0f) != 0x0f && c->light[i + 0x01] < l)                 fill(c, + 0x01, l);         if((i&0x0f) != 0x00 && c->light[i - 0x01] < l)                 fill(c, - 0x01, l);         if((i&0xf0) != 0xf0 && c->light[i + 0x10] < l)                 fill(c, + 0x10, l);         if((i&0xf0) != 0x00 && c->light[i - 0x10] < l)                 fill(c, - 0x10, l);         if((i&0xff00) != 0x0000 && c->light[i - 0x0100] < l)                 fill(c, - 0x0100, l);         if((i&0xff00) != 0xff00 && c->light[i + 0x0100] < l)                 fill(c, + 0x0100, l); }

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