float back_dist;
// all movement is based on t_frame.
-float t_frame; // length of this frame (in ticks = 1/20th second)
+float t_frame; // length of this frame (in ticks = 1/20th second) adjusted for gamespeed
int ms_frame; // length of this frame (milliseconds)
int ms_end; // end of this frame (milliseconds)
int row_inc;
double theta, r;
- n = 12.0 * t_frame;
+ n = 24.0 * t_frame;
pixel = s->pixels;
row_inc = s->pitch/sizeof(uint16_t) - s->w;
colorkey = s->format->colorkey;
void
-new_engine_dots(int n, int dir) {
+new_engine_dots(float time_span, int dir) {
int i;
+ int n = time_span * ENGINE_DOTS_PER_TIC;
float a, r; // angle, random length
float dx, dy;
float hx, hy; // half ship width/height.
static const int s[4] = { 2, 1, 0, 1 };
+ float time;
+ float accelh, accelv, past_ship_dx, past_ship_dy;
hx = ship.image->w / 2;
hy = ship.image->h / 2;
dy = r * -sin(a); // screen y is "backwards".
dotptr->active = 1;
- dotptr->x = ship.x + s[dir]*hx + (frnd()-0.5)*3;
- dotptr->y = ship.y + s[(dir+1)&3]*hy + (frnd()-0.5)*3;
+
+ // dot was created at a random time during the time span
+ time = frnd() * time_span; // this is how long ago
+
+ // calculate how fast the ship was going when this engine dot was
+ // created (as if it had a smoothe accelleration). This is used in
+ // determining the velocity of the dots, but not their starting
+ // location.
+ accelh = ((ship.jets >> 2) & 1) - (ship.jets & 1);
+ accelh *= THRUSTER_STRENGTH * time;
+ past_ship_dx = ship.dx - accelh;
+ accelv = ((ship.jets >> 1) & 1) - ((ship.jets >> 3) & 1);
+ accelv *= THRUSTER_STRENGTH * time;
+ past_ship_dy = ship.dy - accelv;
+
+ // the starting position (not speed) of the dot is calculated as
+ // though the ship were traveling at a constant speed for this
+ // time_span.
+ dotptr->x = (ship.x - (ship.dx - screendx) * time) + s[dir]*hx;
+ dotptr->y = (ship.y - (ship.dy - screendy) * time) + s[(dir+1)&3]*hy;
if(dir&1) {
- dotptr->dx = ship.dx + 2*dx;
- dotptr->dy = ship.dy + 20*dy;
+ dotptr->dx = past_ship_dx + 2*dx;
+ dotptr->dy = past_ship_dy + 20*dy;
dotptr->life = 60 * fabs(dy);
} else {
- dotptr->dx = ship.dx + 20*dx;
- dotptr->dy = ship.dy + 2*dy;
+ dotptr->dx = past_ship_dx + 20*dx;
+ dotptr->dy = past_ship_dy + 2*dy;
dotptr->life = 60 * fabs(dx);
}
+ // move the dot as though it were created in the past
+ dotptr->x += (dotptr->dx - screendx) * time;
+ dotptr->y += (dotptr->dy - screendy) * time;
+
if(dotptr - edot < MAXENGINEDOTS-1) dotptr++;
else dotptr = edot;
}
}
void
+move_engine_dots() {
+ int i;
+ for(i = 0; i<MAXENGINEDOTS; i++) {
+ if(!edot[i].active) {
+ continue;
+ }
+ edot[i].x += (edot[i].dx - screendx)*t_frame;
+ edot[i].y += (edot[i].dy - screendy)*t_frame;
+ edot[i].life -= t_frame*3;
+ if(edot[i].life < 0 || edot[i].x<0 || edot[i].x >= XSIZE || edot[i].y < 0 || edot[i].y >= YSIZE) {
+ edot[i].active = 0;
+ }
+ }
+}
+
+void
draw_engine_dots(SDL_Surface *s) {
int i;
uint16_t c;
Sprite *hit;
for(i = 0; i<MAXENGINEDOTS; i++) {
- if(!edot[i].active) continue;
- edot[i].x += (edot[i].dx - screendx)*t_frame;
- edot[i].y += (edot[i].dy - screendy)*t_frame;
- edot[i].life -= t_frame*3;
- if(edot[i].life < 0
- || edot[i].x<0 || edot[i].x >= XSIZE
- || edot[i].y<0 || edot[i].y >= YSIZE) {
- edot[i].active = 0;
+ if(!edot[i].active) {
continue;
}
// check collisions
drawdots(SDL_Surface *s) {
int m;
- // Create engine dots out the side we're moving from
+ move_engine_dots();
+
+ // Create engine dots
for(m = 0; m<4; m++) {
if(ship.jets & 1<<m) { // 'jets' is a bit field
- new_engine_dots(200.0*t_frame,m);
+ new_engine_dots(t_frame,m);
}
}
- move_dust();
+ move_dust(t_frame);
SDL_LockSurface(s);
draw_dust(s);
}
}
- new_rocks();
+ new_rocks(t_frame);
// SCROLLING
tmp = (ship.y+ship.dy*t_frame-YSCROLLTO)/25 + (ship.dy-screendy);
bangx += (bangdx - screendx)*t_frame;
bangy += (bangdy - screendy)*t_frame;
- move_sprites();
+ move_sprites(t_frame);
// BOUNCE off left or right edge of screen
if(state == GAMEPLAY) {
if(!paused) {
- if(keystate[SDLK_LEFT] | keystate[SDLK_h]) { ship.dx -= 1.5*t_frame; ship.jets |= 1<<0;}
- if(keystate[SDLK_DOWN] | keystate[SDLK_t]) { ship.dy += 1.5*t_frame; ship.jets |= 1<<1;}
- if(keystate[SDLK_RIGHT] | keystate[SDLK_n]) { ship.dx += 1.5*t_frame; ship.jets |= 1<<2;}
- if(keystate[SDLK_UP] | keystate[SDLK_c]) { ship.dy -= 1.5*t_frame; ship.jets |= 1<<3;}
+ // FIXME why is this at the bottom? Shouldn't it be up before the ship movement?
+ if(keystate[SDLK_LEFT] || keystate[SDLK_h]) { ship.dx -= THRUSTER_STRENGTH*t_frame; ship.jets |= 1<<0;}
+ if(keystate[SDLK_DOWN] || keystate[SDLK_t]) { ship.dy += THRUSTER_STRENGTH*t_frame; ship.jets |= 1<<1;}
+ if(keystate[SDLK_RIGHT] || keystate[SDLK_n]) { ship.dx += THRUSTER_STRENGTH*t_frame; ship.jets |= 1<<2;}
+ if(keystate[SDLK_UP] || keystate[SDLK_c]) { ship.dy -= THRUSTER_STRENGTH*t_frame; ship.jets |= 1<<3;}
if(keystate[SDLK_3]) { SDL_SaveBMP(surf_screen, "snapshot.bmp"); }
}