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/*
* physics.c
*
* Calculate what happens
*
* (c) 2008 Thomas White <taw27@cam.ac.uk>
*
* thrust3d - a silly game
*
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <SDL.h>
#include <math.h>
#include "types.h"
#include "model.h"
#include "game.h"
#include "utils.h"
/* Acceleration due to gravity in metres per millisecond per millisecond */
#define GRAVITY (9.81e-6)
/* Acceleration due to booster rocket, metres per ms per ms */
#define THRUST (GRAVITY*2)
/* Acceleration due to forwards/backwards thrusters, m per ms per ms */
#define FTHRUST (GRAVITY*0.5)
/* Air friction in (m per ms per ms) per (m per ms) */
#define FRICTION 0.0008
/* Lander craft turning speed in radians per ms per ms */
#define YAWTHRUST (M_PI/3000000)
/* Conversion factor between friction and 'yawthrust' */
#define TORQUE 1
static void physics_process(ModelInstance *obj, Uint32 dt) {
/* Air friction */
if ( obj->vx > 0.0 ) {
obj->vx -= FRICTION * dt * obj->vx;
if ( obj->vx < 0.0 ) obj->vx = 0.0;
} else {
obj->vx += FRICTION * dt * -obj->vx;
if ( obj->vx > 0.0 ) obj->vx = 0.0;
}
if ( obj->vy > 0.0 ) {
obj->vy -= FRICTION * dt * obj->vy;
if ( obj->vy < 0.0 ) obj->vy = 0.0;
} else {
obj->vy += FRICTION * dt * -obj->vy;
if ( obj->vy > 0.0 ) obj->vy = 0.0;
}
if ( obj->vz > 0.0 ) {
obj->vz -= FRICTION * dt * obj->vz;
if ( obj->vz < 0.0 ) obj->vz = 0.0;
} else {
obj->vz += FRICTION * dt * -obj->vz;
if ( obj->vz > 0.0 ) obj->vz = 0.0;
}
if ( obj->yawspeed > 0.0 ) {
obj->yawspeed -= FRICTION * dt * obj->yawspeed * TORQUE;
if ( obj->yawspeed < 0.0 ) obj->yawspeed = 0.0;
} else {
obj->yawspeed += FRICTION * dt * -obj->yawspeed * TORQUE;
if ( obj->yawspeed > 0.0 ) obj->yawspeed = 0.0;
}
/* Gravity */
if ( obj->attribs & OBJ_GRAVITY ) obj->vz -= GRAVITY * dt;
/* Take a step */
obj->x += obj->vx * dt;
obj->y += obj->vy * dt;
obj->z += obj->vz * dt;
obj->yaw += obj->yawspeed * dt;
if ( obj->yaw < -M_PI ) obj->yaw += 2*M_PI;
if ( obj->yaw > M_PI ) obj->yaw -= 2*M_PI;
}
void physics_step(Game *game) {
int i, j;
Uint32 dt, t;
t = SDL_GetTicks();
dt = t - game->tlast;
/* Handle things specific to the lander craft */
if ( game->thrusting ) {
game->lander->vz += THRUST * dt;
}
if ( game->forward ) {
game->lander->vx += sinf(game->lander->yaw) * FTHRUST * dt;
game->lander->vy += cosf(game->lander->yaw) * FTHRUST * dt;
} else if ( game->reverse ) {
game->lander->vx -= sinf(game->lander->yaw) * FTHRUST * dt;
game->lander->vy -= cosf(game->lander->yaw) * FTHRUST * dt;
}
if ( game->turn_left ) {
game->lander->yawspeed -= YAWTHRUST * dt; /* -ve yaw is "left" */
}
if ( game->turn_right ) {
game->lander->yawspeed += YAWTHRUST *dt; /* +ve yaw is "right" */
}
physics_process(game->lander, dt);
game_check_handoff(game);
for ( j=0; j<game->num_rooms; j++ ) {
Room *room;
room = game->rooms[j];
if ( room == NULL ) return;
for ( i=0; i<room->num_objects; i++ ) {
ModelInstance *obj;
obj = room->objects[i];
if ( obj == NULL ) continue;
physics_process(obj, dt);
}
}
//game->view_angle = deg2rad(30.0 - 30.0 * game->lander->vz/0.015);
game->tlast = t;
}
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