First try with binary scaling

This commit is contained in:
Neale Pickett 2010-06-25 16:15:09 -06:00
commit 4c3e1af017
7 changed files with 508 additions and 0 deletions

6
Makefile Normal file
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all: test
test: test-tanks
./test-tanks
test-tanks: test-tanks.o ctanks.o

159
brad.c Normal file
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#include <stdlib.h>
#include "brad.h"
#ifndef max
#define max(a,b) (((a) > (b)) ? (a) : (b))
#define min(a,b) (((a) < (b)) ? (a) : (b))
#endif
/* Approximate vector length
*
* http://www.flipcode.com/archives/Fast_Approximate_Distance_Functions.shtml
*
* (1007/1024) * 256 == 251.75
* (441/1024) * 256 == 110.25
*/
bs_t
bs_approx_dist(bs_t dx, bs_t dy)
{
bs_t x = abs(dx);
bs_t y = abs(dy);
return (252 * max(x, y)) + (110 * min(x, y));
}
static bs_t bs_cos_table[] = {
256, 256, 256, 255, 255, 254, 253, 252,
251, 250, 248, 247, 245, 243, 241, 239,
237, 234, 231, 229, 226, 223, 220, 216,
213, 209, 206, 202, 198, 194, 190, 185,
181, 177, 172, 167, 162, 157, 152, 147,
142, 137, 132, 126, 121, 115, 109, 104,
98, 92, 86, 80, 74, 68, 62, 56,
50, 44, 38, 31, 25, 19, 13, 6,
0
};
bs_t
bs_cos(brad_t angle)
{
brad_t cos;
bs_t a;
a = abs(angle) % 128;
if (a > 64) {
a = 128 - a;
}
cos = bs_cos_table[a];
a = abs(angle) % 256;
if ((a > 64) && (a < 192)) {
cos = -cos;
}
return cos;
}
bs_t
bs_sin(brad_t angle)
{
return bs_cos(64 - angle);
}
bs_t
bs_tan(brad_t angle)
{
return bs_sin(angle) / bs_cos(angle);
}
static brad_t bs_asin_table[] = {
0, 0, 1, 1, 1, 2, 2, 2,
3, 3, 3, 4, 4, 4, 4, 5,
5, 5, 6, 6, 6, 7, 7, 7,
8, 8, 8, 9, 9, 9, 10, 10,
10, 11, 11, 11, 11, 12, 12, 12,
13, 13, 13, 14, 14, 14, 15, 15,
15, 16, 16, 16, 17, 17, 17, 18,
18, 18, 19, 19, 19, 20, 20, 20,
21, 21, 21, 22, 22, 22, 23, 23,
23, 24, 24, 24, 25, 25, 25, 26,
26, 26, 27, 27, 27, 28, 28, 28,
29, 29, 29, 30, 30, 30, 31, 31,
31, 32, 32, 32, 33, 33, 33, 34,
34, 34, 35, 35, 35, 36, 36, 37,
37, 37, 38, 38, 38, 39, 39, 39,
40, 40, 40, 41, 41, 42, 42, 42,
43, 43, 43, 44, 44, 45, 45, 45,
46, 46, 46, 47, 47, 48, 48, 48,
49, 49, 49, 50, 50, 51, 51, 51,
52, 52, 53, 53, 53, 54, 54, 55,
55, 55, 56, 56, 57, 57, 57, 58,
58, 59, 59, 60, 60, 60, 61, 61,
62, 62, 63, 63, 64, 64, 64, 65,
65, 66, 66, 67, 67, 68, 68, 69,
69, 70, 70, 71, 71, 72, 72, 73,
73, 74, 74, 75, 75, 76, 76, 77,
77, 78, 78, 79, 80, 80, 81, 81,
82, 82, 83, 84, 84, 85, 86, 86,
87, 87, 88, 89, 90, 90, 91, 92,
92, 93, 94, 95, 96, 96, 97, 98,
99, 100, 101, 102, 103, 104, 105, 106,
108, 109, 110, 112, 114, 116, 118, 121,
128
};
brad_t
bs_asin(bs_t n)
{
bs_t a = abs(n);
brad_t ret;
if (a > 256) {
return 0;
}
ret = bs_asin_table[a];
if (n < 0) {
ret = -ret;
}
return ret;
}
brad_t
bs_acos(bs_t n)
{
return 128 - bs_asin(n);
}
brad_t
bs_atan2(bs_t y, bs_t x)
{
bs_t r = bs_approx_dist(x, y);
brad_t t;
t = bs_acos(x / r);
if (y < 0) {
t = 256 - t;
}
return t;
}
#include <math.h>
#include <stdio.h>
#define PI 3.14159265358979323846
int
main()
{
int i, j;
float f;
int t;
for (i = 0; i < 257; i += 1) {
for (j = 0; j < 257; j += 1) {
f = sqrt(i*i + j*j);
t = bs_approx_dist(i, j);
printf("%d %d %d\n", i, (int)round(f*256)/256, t/256);
}
}
return 0;
}

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brad.h Normal file
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#ifndef __BRAD_H__
#define __BRAD_H__
/** Binary scaling library
*
* There are B8 binary scaled ints. That means the 8 lowest bits are
* the fractional part. To convert to a float you'd just divide by 256.
*
* The trig functions use brads (Binary Radians). There are 128 brads
* in 2pi radians. One brad is about 1.4 degrees. Using brads makes
* trig really fast on a binary computer, and reallier faster on a
* binary computer without an FPU.
*
* You must be careful not to overflow your bs_t. For instance, I wrote
* this library for a game with a 2^9-pixel-wide playfield. That's
* 2^17 B8, but I also needed to do distance calculations, which
* requires squaring things. 2^34 is obviously too big to represent in
* 32 bits.
*
* C's type system leaves a lot to be desired when it comes to making
* sure you're not mixing these things up with normal ints. Be careful!
*/
/* Just to make it clear what scale these functions are dealing with */
typedef struct {
int v;
} bs_t;
typedef int brad_t;
/* If you change this, you must also change the lookup tables in
* brad.c. Don't change this. */
#define BINARY_SCALE 8
#define BS_DENOMINATOR 1 << BINARY_SCALE
#define bs_to_int(n) ((n) >> BINARY_SCALE)
#define bs_of_int(i) ((i) << BINARY_SCALE)
bs_t bs_cos(brad_t angle);
bs_t bs_sin(brad_t angle);
bs_t bs_tan(brad_t angle);
brad_t bs_acos(bs_t angle);
brad_t bs_asin(bs_t angle);
bs_t bs_mul(bs_t a, bs_t b);
bs_t bs_div(bs_t a, bs_t b);
bs_t bs_approx_dist(bs_t dx, bs_t dy);
#endif /* __BRAD_H__ */

25
brad.py Executable file
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#! /usr/bin/python
# Binary radians with B12 binary scaling (multiply floats by 256)
# pi radians = 128 brads
import math
brad2rad = math.pi/128
print "static bs_t bs_cos_table[] = {"
for i in range(129):
r = (i * math.pi) / 128.0
cos = math.sin(r)
bcos = int(round(cos * 256))
print ("%3d," % bcos),
print "}"
print "static brad_t bs_asin_table[] = {"
for i in range(257):
f = i / 256.0
acos = math.asin(f)
bacos = int(round(256 * acos / math.pi))
print ("%3d," % bacos),
print "}"

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ctanks.c Normal file
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#include <string.h>
#include <stdlib.h>
#include "brad.h"
#include "ctanks.h"
void
tank_init(struct tank *tank, tank_run_func *run, void *udata)
{
memset(tank, 0, sizeof(*tank));
tank->run = run;
tank->udata = udata;
}
int
tank_fire_ready(struct tank *tank)
{
return (! tank->turret.recharge);
}
void
tank_fire(struct tank *tank)
{
tank->turret.firing = tank_fire_ready(tank);
}
void
tank_set_speed(struct tank *tank, bs_t left, bs_t right)
{
tank->speed.desired[0] = left;
tank->speed.desired[1] = right;
}
brad_t
tank_get_turret(struct tank *tank)
{
return tank->turret.current;
}
void
tank_set_turret(struct tank *tank, brad_t angle)
{
tank->turret.desired = angle;
}
int
tank_get_sensor(struct tank *tank, int sensor_num)
{
if ((sensor < 0) || (sensor > MAX_SENSORS)) {
return 0;
}
return tank->sensor[sensor_num].triggered;
}
void
tank_set_led(struct tank *tank, int active)
{
tank->led = active;
}
/** Return distance^2 between tanks a and b.
*
* Comparing this against sensor_range^2 will tell you whether the tanks
* are within sensor range of one another. Similarly, comparing it
* against (2*tank_radius)^2 will tell you if they've collided.
*
*/
bs_t
tank_dist2(struct tanks_game *game, struct tank *a, struct tank *b)
{
bs_t d[2];
int i;
for (i = 0; i < 2; i += 1) {
d[i] = abs(a.position[i] - b.position[i]);
d[i] = min(game.size[i] - dx[i], dx[i]);
}
return ((d[0] * d[0]) + (d[1] * d[1]));
}
void
do_shit_with(struct tanks_game *game,
struct tank *this,
struct tank *that)
{
bs_t vector[2];
int dist2; /* Integer to avoid overflow! */
bs_t xpos; /* Translated position */
int i;
/* Don't bother if one is dead */
if ((this->killer) || (that->killer)) {
return;
}
/* Establish shortest vector from center of this to center of that,
* taking wrapping into account */
for (i = 0; i < 2; i += 1) {
bs_t halfsize = game->size[i] / 2;
/* XXX: is there a more elegant way to do this? */
vector[i] = that->position[i] - this->position[i];
if (2*vector[i] > game->size[i]) {
vector[i] -= game->size[i];
} else if (2*vector[i] < game->size[i]) {
vector[i] += game->size[i];
}
}
/* Compute distance^2 for range comparisons */
dist2 = ((bs_to_int(vector[0]) * bs_to_int(vector[0])) +
(bs_to_int(vector[1]) * bs_to_int(vector[1])));
/* If they're not within sensor range, there's nothing to do. */
if (dist2 > TANK_SENSOR_ADJ2) {
return;
}
/* Did they collide? Oh, goody! */
if (dist2 < TANK_COLLISION_ADJ2) {
/* XXX: kill both tanks */
return;
}
/* Has anybody been shot? */
/* Translate other tank's position to make us the origin */
for (i = 0; i < 2; i += 1) {
xpos[i] = that->position[i] - this->position[i];
}
/* Calculate sensors */
for (i = 0; i < this->num_sensors; i += 1) {
brad_t theta;
if (dist2 < this->sensor[i].range_adj2) {
continue;
}
/* Translate other tank so that we're the origin */
}
}
void
tanks_run_turn(struct tanks_game *game, struct tank *tanks, int ntanks)
{
int i, j;
for (i = 0; i < ntanks; i += 1) {
for (j = i + 1; j < ntanks, j += 1) {
do_shit_with(game, &(tanks[i]), &(tanks[j]));
}
tanks_print_tank(game, &(tanks[i]));
tanks_move(game, &(tanks[i]));
}
}

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ctanks.h Normal file
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#ifndef __CTANKS_H__
#define __CTANKS_H__
#include "brad.h"
/* Some useful constants */
#define TANK_MAX_SENSORS 10
#define TANK_RADIUS ((bs_t)1920)
#define TANK_SENSOR_RANGE ((int)100)
/* (tank radius + tank radius)^2 */
#define TANK_COLLISION_ADJ2 \
bs_to_int((TANK_RADIUS + TANK_RADIUS) * (TANK_RADIUS + TANK_RADIUS))
/* (Sensor range + tank radius)^2
* If the distance^2 to the center of a tank <= TANK_SENSOR_ADJ2,
* that tank is within sensor range. */
#define TANK_SENSOR_ADJ2 ((int)11556)
struct tanks_game {
bs_t size[2]; /* dimensions of playing field */
};
struct tank;
struct sensor {
brad_t angle;
brad_t width;
int range;
int range_adj2; /* (range + TANK_RADIUS)^2 */
int turret; /* Mounted to turret? */
int triggered;
};
typedef void tank_run_func(struct tank *, void *);
struct tank {
bs_t position[2]; /* Current position on the board */
brad_t angle; /* Current orientation */
struct {
bs_t current[2]; /* Current tread speed */
bs_t desired[2]; /* Desired tread speed */
} speed;
struct {
brad_t current; /* Current turret angle */
brad_t desired; /* Desired turret angle */
int firing; /* True if firing this turn */
int recharge; /* Turns until gun is recharged */
} turret;
struct sensor sensor[MAX_SENSORS]; /* Sensor array */
int num_sensors; /* Number of sensors */
int led; /* State of the LED */
struct tank *killer; /* Killer, or NULL if alive */
char *cause_death; /* Cause of death */
tank_run_func *run; /* Function to run a tank */
void *udata; /* Argument to pass to run */
};
void tank_init(struct tank *tank, tank_run_func *run, void *udata);
/*
*
* Tanks API for scripts
*
*/
/** Has the turret recharged? */
int tank_fire_ready(struct tank *tank);
/** Fire! */
void tank_fire(struct tank *tank);
/** Set desired speed */
void tank_set_speed(struct tank *tank, int left, int right);
/** Get the current turret angle */
int tank_get_turret(struct tank *tank);
/** Set the desired turret angle */
void tank_set_turret(struct tank *tank, int angle);
/** Is a sensor active? */
int tank_get_sensor(struct tank *tank, int sensor_num);
/** Set the LED state */
void tank_set_led(struct tank *tank, int active);
#endif /* __CTANKS_H__ */

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#include <stdio.h>
#include <math.h>
#include "ctanks.h"
void
test_run(struct tank *tank, void *unused)
{
tank_set_speed(tank, 30, 50);
tank_set_turret(tank, fmod(tank->turret.desired + 0.2, 2*PI));
}
int
main(int argc, char *argv[])
{
struct tank mytank;
int i;
tank_init(&mytank, test_run, NULL);
printf("hi\n");
for (i = 0; i < 4; i += 1) {
printf("%f\n", mytank.turret.desired);
mytank.run(&mytank, mytank.udata);
}
return 0;
}