Starfield code

OK finally got my $2 breakout board from China, debugged my horrible code and got the starfield working. I had a few oversights coming from platforms that had better hardware, such as bytes being unsigned, string literals being costly and structures add up when you have a lot of them. I tuned the constants just below artifacts began appearing. I suppose lowering the resolution would allow more stars onscreen but for now 16 still creates the effect.

In anycase, here is the working final code, its your typical Starfield/hyperspace view thing with stars wizzing by in pseudo-3D. you can adjust the Speed with up/down on the on-board controller.

/** Starfield for Hackvision

By Cord Rehn 2012 **/





#include 

#include 

#include 

#include 

#include 





#define TV_W 136

#define TV_H 98



TVout tv;



#define NUM_STARS 16

#define Z_MAX 6.f



byte SPEED;

char speed_string[11], s[4];



prog_char s0[] PROGMEM = "SPEED ";



PROGMEM const char *strings[] = {s0};



struct Star {

int x, y;

byte old_x, old_y;

float z;

} Starfield[NUM_STARS];



void initStar(int index) {

Starfield[index].x = random(TV_W*2) - TV_W;

Starfield[index].y = random(TV_H*2) - TV_H;

Starfield[index].old_x = Starfield[index].old_y = 255;

Starfield[index].z = Z_MAX;

}



void setSpeed(byte speed) {

tv.tone(speed < SPEED ? 800 : 1046, 20);



SPEED = speed;

speed_string[0] = s[0] = '';

strcpy_P(speed_string, (char *)pgm_read_word(&(strings[0])));

snprintf(s, 4, "%d  ", SPEED); // 2 spaces are important, clears the 2nd and 3rd digit spots for a 1 digit speed when printed

strncat(speed_string, s, 11);

}



void setup()  {

// If pin 12 is pulled LOW, then the PAL jumper is shorted.

pinMode(12, INPUT);

digitalWrite(12, HIGH);



if (digitalRead(12) == LOW)

tv.begin(_PAL, TV_W, TV_H);

else

tv.begin(_NTSC, TV_W, TV_H);



tv.select_font(font4x6);

randomSeed(analogRead(0));



tv.delay(10);



// init star field

for (int i = 0; i < NUM_STARS; ++i) {

initStar(i);

Starfield.z = random(Z_MAX+1);

}



setSpeed(100);

}





void loop() {

// input

if (Controller.upPressed() && SPEED != 255)

setSpeed(SPEED + 1);

else if (Controller.downPressed() && SPEED != 0)

setSpeed(SPEED - 1);



// draw

for (int i = 0; i < NUM_STARS; ++i) {

if (Starfield.old_x != 255)

tv.set_pixel(Starfield.old_x, Starfield.old_y, 0);



Starfield.z -= (float)SPEED/1000.f;

if (Starfield.z < (float)SPEED/1000.f)

initStar(i);



byte x = TV_W / 2 + Starfield.x / Starfield.z,

y = TV_H / 2 + Starfield.y / Starfield.z;

if (x < 0 || y < 0 || x >= TV_W || y >= TV_H)

initStar(i);

else {

tv.set_pixel(x, y, 1);

Starfield.old_x = x;

Starfield.old_y = y;

}

}



tv.print(0, 0, speed_string);

}