ref: 38de7eaca1fa15e005bc0065adc7019dfaedae38
dir: /r_fog.h/
typedef struct fog_t fog_t; struct fog_t { pixel64_t v; pixel64_t d; }; #define fogstep(f) do{ \ (f).v += (f).d; \ }while(0) static inline byte z2foga(uzint z) { float d; unsigned x; if(z <= 0) return 0; x = 0xffffffffU / z; d = exp2f(-fogvars.density * x * x); return 255 - 255*d; } static inline pixel64_t pixto64(pixel_t p) { return (pixel64_t)((p>>24)&0xff)<<56 | (pixel64_t)((p>>16)&0xff)<<40 | (pixel64_t)((p>> 8)&0xff)<<24 | (pixel64_t)((p>> 0)&0xff)<< 8; } static inline pixel_t pixfrom64(pixel64_t p) { return ((p>>56)&0xff)<<24 | ((p>>40)&0xff)<<16 | ((p>>24)&0xff)<<8 | ((p>>8)&0xff)<<0; } static inline pixel_t blendfog(pixel_t pix, fog_t fog) { pixel_t a = pixfrom64(fog.v); pixel_t b = mulalpha(pix, 0xff - (fog.v>>56)); return a + b; } static inline bool fogcalc(uzint zi0, uzint zi1, int cnt, fog_t *f) { int v, e; pixel64_t x; if((v = z2foga(zi0)) == 0 || (e = z2foga(zi1)) == 0) return false; f->v = pixto64(mulalpha(fogvars.pix, v)); x = pixto64(mulalpha(fogvars.pix, (e<v ? v-e : e-v))); f->d = (((x & (0xffffULL<<48))/cnt) & (0xffffULL<<48)) | (((x & (0xffffULL<<32))/cnt) & (0xffffULL<<32)) | (((x & (0xffffULL<<16))/cnt) & (0xffffULL<<16)) | (((x & (0xffffULL<< 0))/cnt) & (0xffffULL<< 0)); if(e < v) f->d = -f->d; return true; }