Descent3/fix/fix.cpp

/*
 * $Logfile: /DescentIII/Main/fix/fix.cpp $
 * $Revision: 6 $
 * $Date: 4/22/99 8:29p $
 * $Author: Kevin $
 *
 *  Fixed-point math functions, including trig & float conversions
 *
 * $Log: /DescentIII/Main/fix/fix.cpp $
 * 
 * 6     4/22/99 8:29p Kevin
 * made psrand.h come after stdlib.h
 * 
 * 5     4/21/99 11:05a Kevin
 * new ps_rand and ps_srand to replace rand & srand
 * 
 * 4     8/26/97 10:15a Jason
 * corrected the FixCeil function
 * 
 * 3     8/22/97 12:34p Jason
 * added FixCeil and FixFloor
 * 
 * 2     8/21/97 5:57p Samir
 * Added initialization of random number generator.
 * 
 * 7     2/27/97 4:47 PM Jeremy
 * moved inline assembly language functions processor for
 * fixmul/fixdiv/fixmuldiv into fixmac.h and fixwin32.h
 * 
 * 6     2/12/97 5:35p Jason
 * fixed yet another dumb syntax error...will I ever learn?
 * 
 * 5     2/12/97 5:34p Jason
 * fixed dumb syntax error
 * 
 * 4     2/12/97 5:27p Jason
 * implemented asin,acos,atan2
 * 
 * 3     2/10/97 1:57p Jason
 * changed FloatToFix back to what it originally was
 * 
 * 2     2/07/97 5:44p Matt
 * Moved fixed-point math funcs from vecmat to fix
 * Changed trig functions to use small table like D2
 *
 * $NoKeywords: $
 */

#include "fix.h"

#include <time.h>
#include <stdlib.h>
#include "psrand.h"
//Tables for trig functions
float sincos_table[321];				//256 entries + 64 sin-only + 1 for interpolation
angle asin_table[257];					// 1 quadrants worth, +1 for interpolation
angle acos_table[257];					

#define PI 3.141592654

//Generate the data for the trig tables
void InitMathTables ()
{
	int i;
	float rad,s,c;

	for (i=0;i<321;i++) {
		rad = (float) ((double) i / 256.0 * 2 * PI);
		sincos_table[i] = (float) sin(rad);
	}

	for (i=0;i<256;i++) {
				
		s=asin((float)i/256.0);
		c=acos((float)i/256.0);

		s=(s/(PI*2));
		c=(c/(PI*2));
		
		asin_table[i] = FloatToFix(s);
		acos_table[i] = FloatToFix(c);
	}
	
	asin_table[256]=asin_table[255];
	acos_table[256]=acos_table[255];

//	Initialize a random seed.
	ps_srand(time(NULL));
}

//Returns the sine of the given angle.  Linearly interpolates between two entries in a 256-entry table
float FixSin(angle a)
{
   int i,f;
   float s0,s1;

   i = (a>>8)&0xff;
   f = a&0xff;

   s0 = sincos_table[i];
   s1 = sincos_table[i+1];
   return (float) (s0 + ((s1 - s0) * (double) f / 256.0));
}

//Returns the cosine of the given angle.  Linearly interpolates between two entries in a 256-entry table
float FixCos(angle a)
{
   int i,f;
   float c0,c1;

   i = (a>>8)&0xff;
   f = a&0xff;

   c0 = sincos_table[i+64];
   c1 = sincos_table[i+64+1];
   return (float) (c0 + ((c1 - c0) * (double) f / 256.0));
}

//Returns the sine of the given angle, but does no interpolation
float FixSinFast(angle a)
{
   int i;

   i = ((a+0x80)>>8)&0xff;

   return sincos_table[i];
}

//Returns the cosine of the given angle, but does no interpolation
float FixCosFast(angle a)
{
   int i;

   i = ((a+0x80)>>8)&0xff;

   return sincos_table[i+64];
}

// use this instead of:
// for:  (int)floor(x+0.5f) use FloatRound(x)
//       (int)ceil(x-0.5f)  use FloatRound(x)
//       (int)floor(x-0.5f) use FloatRound(x-1.0f)
//       (int)floor(x)      use FloatRound(x-0.5f)
// for values in the range -2048 to 2048

// Set a vector to {0,0,0}
int FloatRound( float x )
{
	float nf;
	nf = x + 8390656.0f;
	return ((*((int *)&nf)) & 0x7FFFFF)-2048;
}

// A fast way to convert floats to fix
fix FloatToFixFast( float x )
{

	float nf;
	nf = x*65536.0f + 8390656.0f;
	return ((*((int *)&nf)) & 0x7FFFFF)-2048;
}

//Get rid of the "no return value" warnings in the next three functions
#pragma warning (disable:4035)

//compute inverse sine
angle FixAsin(float v)
{
	fix vv;
	int i,f,aa;

	vv = FloatToFix(fabs(v));

	if (vv >= F1_0)		//check for out of range
		return 0x4000;

	i = (vv>>8)&0xff;
	f = vv&0xff;

	aa = asin_table[i];
	aa = aa + (((asin_table[i+1] - aa) * f)>>8);

	if (v < 0)
		aa = F1_0-aa;

	return aa;
}

//compute inverse cosine
angle FixAcos(float v)
{
	fix vv;
	int i,f,aa;

	vv = FloatToFix(fabs(v));

	if (vv >= F1_0)		//check for out of range
		return 0;

	i = (vv>>8)&0xff;
	f = vv&0xff;

	aa = acos_table[i];
	aa = aa + (((acos_table[i+1] - aa) * f)>>8);

	if (v < 0)
		aa = 0x8000 - aa;

	return aa;
}

//given cos & sin of an angle, return that angle.
//parms need not be normalized, that is, the ratio of the parms cos/sin must
//equal the ratio of the actual cos & sin for the result angle, but the parms 
//need not be the actual cos & sin.  
//NOTE: this is different from the standard C atan2, since it is left-handed.
angle FixAtan2(float cos,float sin)
{
	float q,m;
	angle t;
	
	//find smaller of two


	q=(sin*sin)+(cos*cos);
	
	m = sqrt(q);

	if (m==0)
		return 0;

	if (fabs(sin) < fabs(cos)) 
	{
		//sin is smaller, use arcsin
		t = FixAsin(sin/m);
		if (cos<0)
			t = 0x8000 - t;
	
		return t;
	}
	else 
	{
		t = FixAcos(cos/m);
		if (sin<0)
			t = F1_0-t;
	
		return t;
	}

}


// Does a ceiling operation on a fixed number
fix FixCeil (fix num)
{
	int int_num;
	fix new_num;

	int_num=FixToInt (num);

	if (num & 0xFFFF)
	{
		new_num=IntToFix(int_num+1);
		return new_num;
	}

	new_num=IntToFix(int_num);
	return (new_num);
}

// Floors a fixed number 
fix FixFloor (fix num)
{
	int int_num=FixToInt (num);

	return (IntToFix (int_num));
}