2 * $Logfile: /Freespace2/code/Math/Floating.cpp $
7 * Low-level floating point math routines
10 * Revision 1.1 2002/05/03 03:28:09 root
14 * 2 10/07/98 10:53a Dave
17 * 1 10/07/98 10:49a Dave
19 * 13 2/26/98 3:28p John
20 * Changed all sqrt's to use fl_sqrt. Took out isqrt function
22 * 12 1/30/98 12:25p Mike
23 * Make frand() not return 1.0, which can cause overflow when indexing
26 * 11 1/26/98 10:43p Mike
27 * Make ships not all zoom away from an impending shockwave at the same
28 * time. Based on ai class and randomness
30 * 10 1/20/98 9:47a Mike
31 * Suppress optimized compiler warnings.
32 * Some secondary weapon work.
34 * 9 1/17/98 3:32p Mike
35 * Add rand_range(), returns random float in min..max.
37 * 8 9/09/97 11:07a Sandeep
38 * fixed warning level 4
40 * 7 8/05/97 10:18a Lawrance
41 * my_rand() being used temporarily instead of rand()
43 * 6 2/17/97 5:18p John
44 * Added a bunch of RCS headers to a bunch of old files that don't have
62 #define LOOKUP_POS (EXP_POS-LOOKUP_BITS)
63 #define SEED_POS (EXP_POS-8)
64 #define TABLE_SIZE (2<<LOOKUP_BITS)
65 #define LOOKUP_MASK (TABLE_SIZE-1)
66 #define GET_EXP(a) (((a) >> EXP_POS) & 0xFF )
67 #define SET_EXP(a) ((a) << EXP_POS )
68 #define GET_EMANT(a) (((a) >> LOOKUP_POS) & LOOKUP_MASK )
69 #define SET_MANTSEED(a) (((unsigned long)(a)) << SEED_POS )
71 static unsigned char iSqrt[TABLE_SIZE];
72 static int iSqrt_inited = 0;
74 int fl_magic = 0x59C00000; //representation of 2^51 + 2^52
75 const float *p_fl_magic = (const float *)&fl_magic;
83 static void MakeInverseSqrtLookupTable()
90 for ( f=0, h=iSqrt; f < TABLE_SIZE; f++ ) {
91 fi.i = ((EXP_BIAS-1)<<EXP_POS) | (f<<LOOKUP_POS);
92 fo.f = 1.0f / fl_sqrt(fi.f);
93 *h++ = (unsigned char)(((fo.i + (1<<(SEED_POS-2))) >>SEED_POS ) & 0xFF);
95 iSqrt[ TABLE_SIZE / 2 ] = 0xFF;
100 float fl_isqrt_c( float x )
102 // unsigned long a = ((union _flint *)(&x))->i;
104 // union _flint seed;
108 t1 = timer_get_microseconds();
109 float r1 = 1.0f / (float)sqrt((double)x);
110 t2 = timer_get_microseconds();
111 // float r2 = fl_isqrt_asm(x);
112 t3 = timer_get_microseconds();
117 /* if ( !iSqrt_inited )
118 MakeInverseSqrtLookupTable();
120 seed.i = SET_EXP(((3*EXP_BIAS-1) - GET_EXP(a)) >> 1 ) | SET_MANTSEED(iSqrt[GET_EMANT(a)]);
122 r = (3.0f - r * r * arg ) * r * 0.5f;
123 r = (3.0f - r * r * arg ) * r * 0.5f;
128 // rounds off a floating point number to a multiple of some number
129 float fl_roundoff(float x, int multiple)
131 float half = (float) multiple / 2.0f;
137 return (float) (((int) x / multiple) * multiple);
141 // Return random value in range 0.0..1.0- (1.0- means the closest number less than 1.0)
145 rval = ((float) myrand()) / (RAND_MAX + 1);
149 // Return a floating point number in the range min..max.
150 float frand_range(float min, float max)
155 rval = rval * (max - min) + min;
160 // Call this in the frame interval to get TRUE chance times per second.
161 // If you want it to return TRUE 3 times per second, call it in the frame interval like so:
162 // rand_chance(flFrametime, 3.0f);
163 int rand_chance(float frametime, float chance) // default value for chance = 1.0f.
165 while (--chance > 0.0f)
166 if (frand() < frametime)
169 return frand() < (frametime * (chance + 1.0f));
172 /*fix fl2f( float x )
175 nf = x*65536.0f + 8390656.0f;
176 return ((*((int *)&nf)) & 0x7FFFFF)-2048;
183 >#define MAGIC (((S * S * 16) + (S*.5)) * S)
185 >#pragma inline float2int;
187 >ulong float2int( float d )
189 > double dtemp = MAGIC + d;
190 > return (*(ulong *)&dtemp) - 0x80000000;