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stuff.c
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stuff.c
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/*
This file contains some maths and utility functions. The only ones used at present are:
xpart/ypart - call them with angle x and distance d; they'll give you the x component and y component
of a line in the angle x and the distance d
angle_to_radians - I use a 1024-degree circle in a format called 'angle'. It lets me use lookup tables
radians_to_angle without interpolation for simple trig, and minimises slow floating-point operations.
angle_to_radians takes 'angle' values and turns them into radians; radians_to_angle etc.
grand(n) - random number from 1 to n
*/
#include "config.h"
#include "allegro.h"
#include <math.h>
int turn_towards_angle(int angle, int tangle, int turning);
int delta_turn_towards_angle(int angle, int tangle, int turning);
int turn_towards_angle_forbid(int angle, int tangle, int turning, int forbid);
float lcos(int angle);
float lsin(int angle);
float angle_to_radians(int angle);
// I have no idea why, but the first few elements of cos_table always get corrupted
// unless I put a big fat decoy array just above. A similar thing happens to the
// palette arrays; allegro seems to have a problem with global arrays like these.
float decoy_table [ANGLE_1]; // not used
float cos_table [ANGLE_1];
float sin_table [ANGLE_1];
void init_trig(void)
{
int i;
for (i = 0; i < ANGLE_1; i ++)
{
cos_table [i] = cos(angle_to_radians(i));// * ANGLE_1;
sin_table [i] = sin(angle_to_radians(i));// * ANGLE_1;
}
}
int xpart(int angle, int length)
{
return (cos_table [angle & ANGLE_MASK] * length);
}
int ypart(int angle, int length)
{
return (sin_table [angle & ANGLE_MASK] * length);
}
int fxpart(float angle, int length)
{
return (cos(angle) * length);
}
int fypart(float angle, int length)
{
return (sin(angle) * length);
}
float lcos(int angle)
{
return cos_table [angle & ANGLE_MASK];
}
float lsin(int angle)
{
return sin_table [angle & ANGLE_MASK];
}
float angle_to_radians(int angle)
{
return ((float) angle * PI * 2) / ANGLE_1;
}
int radians_to_angle(float angle)
{
if (angle < 0)
angle += PI * 2;
return (int) ((angle * ANGLE_1) / (PI * 2));
}
fixed angle_to_fixed(int angle)
{
return itofix(angle / ANGLE_TO_FIXED);
}
int grand(int number)
{
if (number == 0)
return 0;
return ((rand() + (rand() << 16)) & 0x7fffffff) % number;
}
// returns the new angle
int turn_towards_angle(int angle, int tangle, int turning)
{
if ((angle < tangle && tangle > angle + ANGLE_2)
|| (angle > tangle && tangle > angle - ANGLE_2))
{
angle -= turning;
// if (angle < 0)
// angle += ANGLE_1;
}
else
{
angle += turning;
// if (angle > ANGLE_1)
// angle -= ANGLE_1;
}
return angle&ANGLE_MASK;
}
int turn_towards_xy(int x1, int y1, int x2, int y2, int angle, int turning)
{
int tangle =
radians_to_angle(atan2((y2 - y1), (x2 - x1)));
if (tangle < 0)
tangle += ANGLE_1;
if (tangle > ANGLE_1)
tangle -= ANGLE_1;
return turn_towards_angle(angle, tangle, turning);
}
// delta version just returns the change needed
int delta_turn_towards_angle(int angle, int tangle, int turning)
{
if ((angle < tangle && tangle > angle + ANGLE_2)
|| (angle > tangle && tangle > angle - ANGLE_2))
{
return turning * -1;
}
return turning;
}
int delta_turn_towards_xy(int x1, int y1, int x2, int y2, int angle, int turning)
{
int tangle =
radians_to_angle(atan2((y2 - y1), (x2 - x1)));
tangle &= ANGLE_MASK;
/* if (tangle < 0)
tangle += ANGLE_1;
if (tangle > ANGLE_1)
tangle -= ANGLE_1;*/
return delta_turn_towards_angle(angle, tangle, turning);
}
int turn_towards_xy_forbid(int x1, int y1, int x2, int y2, int angle, int turning, int forbid)
{
int tangle =
radians_to_angle(atan2((y2 - y1), (x2 - x1)));
if (tangle < 0)
tangle += ANGLE_1;
if (tangle > ANGLE_1)
tangle -= ANGLE_1;
return turn_towards_angle_forbid(angle, tangle, turning, forbid);
}
int turn_towards_angle_forbid(int angle, int tangle, int turning, int forbid)
{
if ((angle < tangle && tangle > angle + ANGLE_2)
|| (angle > tangle && tangle > angle - ANGLE_2))
{
if (forbid == -1)
return angle;
angle -= turning;
if (angle < 0)
angle += ANGLE_1;
}
else
{
if (forbid == 1)
return angle;
angle += turning;
if (angle > ANGLE_1)
angle -= ANGLE_1;
}
return angle;
}
// speed must be at least 4, and a factor of 1024
int pulsate(int speed, int amount, int county)
{
return xpart((county * speed) & ANGLE_MASK, amount);
}
void error_message_out(const char *errm)
{
set_gfx_mode(GFX_TEXT, 0, 0, 0, 0);
allegro_message(errm);
exit(1);
}
int angle_difference(int a1, int a2)
{
int d1, d2;
d1 = (a1 - a2 + ANGLE_1) & ANGLE_MASK;
d2 = (a2 - a1 + ANGLE_1) & ANGLE_MASK;
if (d1 < d2)
return abs(d1) & ANGLE_MASK;
// return abs(d1);
// return abs(d2);
return abs(d2) & ANGLE_MASK;
}
int angle_difference_signed(int a1, int a2)
{
int d1;
d1 = (a2 - a1) & ANGLE_MASK;
// d2 = (a2 - a1 + ANGLE_1) & ANGLE_MASK;
if (d1 > ANGLE_2)
return -ANGLE_1 + d1;
// if (d1 < -ANGLE_2)
//return d1 + ANGLE_1;
return d1;
/*
int d1, d2;
d1 = (a1 - a2 + ANGLE_1) & ANGLE_MASK;
d2 = (a2 - a1 + ANGLE_1) & ANGLE_MASK;
if (abs(d1) < abs(d2))
{
if (d1 > 0)
return d1 & ANGLE_MASK;
return (d1 & ANGLE_MASK) * -1;
}
// return abs(d1);
// return abs(d2);
// return abs(d2) & ANGLE_MASK;
if (d2 > 0)
return d2 & ANGLE_MASK;
return (d2 & ANGLE_MASK) * -1;*/
}
int pos_or_neg(int a)
{
if (grand(2) == 0)
return a;
return a * -1;
}
char coin(void)
{
return rand() & 1;
}