Explosions

**meehanmd** · 04-11-2006

hi, im creating a game throught C++ using the SDL thing (ive already got a little help off you before, thanks by the way) and i was wondering if i could create a kind of explosion lasting one second or so when a collision is detected in the place of where my bad guy is

i create the enemy using

Code:

evil[i] = new Sprite ("U:\\2E3\\hi\\hi\\wood.gif");

and i was wondering if, when a collision is detected could a new picture be drawn (i.e. an explosion) and that picture to stay on screen for about a second

by the way, i use

Code:

evil[i]->alive = false;

to delete my guy off the screen, but that is called in the same place that i want to call explosions and when i create an explosion picture it just goes straight to alive = false before it even gets around to draw the pictures

so basically what i want is

Code:

if (collision == true)
{
create a bad guy on screen for 1 second (or 16 frames because i think thats the speed it runs at)
evil[i]->alive = false; // kill the guy after he has been up for a second
}

thanks if you can help

**Salem** · 04-11-2006

> evil[i]->alive = false;

So have more states
evil[i]->state = alive;
evil[i]->state = exploding;
evil[i]->state = dead;

If you're in the exploding state, have a frame counter to count which frame of the explosion sequence you're supposed to be drawing.

When you get to the last explosion frame, move to the next state (ie dead)

**joeprogrammer** · 04-11-2006

Although you could use a single bitmap for an explosion, a particle engine would make the game look a lot better. I don't know if you're making a 2D game or 3D game, but this should work either way:

http://nehe.gamedev.net/data/lessons....asp?lesson=19

Most particle engines are difficult to make; however, this one is very simple, so it can be made like beginners like me

.

**meehanmd** · 04-12-2006

Originally Posted by Salem

> evil[i]->alive = false;

So have more states
evil[i]->state = alive;
evil[i]->state = exploding;
evil[i]->state = dead;

If you're in the exploding state, have a frame counter to count which frame of the explosion sequence you're supposed to be drawing.

When you get to the last explosion frame, move to the next state (ie dead)

im actually not sure how to work that frame counter

**Salem** · 04-12-2006

You mean like extract a given frame from a GIF animation file?

Code:

if ( state == alive ) {
  // all other alive stuff
  if ( collision() ) {
    state = exploding;
    explodeFrame = 0;
  }
} else if ( state == exploding ) {
  // draw a frame
  explodeFrame++;
  if ( explodeFrame == 16 ) {
    state = dead;
  }
} else if ( state == dead ) {
  // woo hoo
  // add to player score and remove the enemy object
}

**meehanmd** · 04-12-2006

oh, ok, i get that now, but what type will state be or is it a seperate method in my class

**Salem** · 04-12-2006

> but what type will state be
Well you previously had a boolean, alive or dead

So an enum of

Code:

enum eState { alive, exploding, dead };

**meehanmd** · 04-12-2006

im getting a weird error when i run this

Code:

error C2513: 'State' : no variable declared before '='

after i write

Code:

State = exploding;

any idea what it is, it also appears in other places

**Salem** · 04-12-2006

Lemme guess, State is the name of the enum.

Enums are types, so you need
State myState;
myState = exploding;

Much like you would with an int
int count;
count = 2;

**meehanmd** · 04-12-2006

brilliant, thanks, just a few more things left that involve my code, not enums so i should be grand with it. thanks

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