Animating sprites at random rates

Question

I have a program that displays 5 explosions in a line at the same time. I would like to know how to get each explosion to animate at different rates. Here is the code that actually animates the sprites:

//=========================================================================
//
// Helper functions
//
//========================================================================
void Sprite_Draw_Frame(LPDIRECT3DTEXTURE9 texture, int destx, int desty, int framenum, int framew, int frameh, int columns)
{
    D3DXVECTOR3 position( (float)destx, (float)desty, 0);
    D3DCOLOR white = D3DCOLOR_XRGB(255, 255, 255);`

    RECT rect;
    rect.left = (framenum % columns) * framew;
    rect.top = (framenum / columns) * frameh;
    rect.right = rect.left + framew;
    rect.bottom = rect.top + frameh;

    spriteobj->Draw(texture, &rect, NULL, &position, white);
}

void Sprite_Animate(int &frame, int startframe, int endframe, int direction, int &starttime, int delay)
{
    if((int)GetTickCount() > starttime + delay)
    {
        starttime = GetTickCount();

        frame += direction;
        if(frame > endframe) frame = startframe;
        if(frame < startframe) frame = endframe;
    }
}

//============================================================================
//
// Function calls
//
//==============================================================================

Tried to use random numbers for the delay variable in Sprite_Animate so that the frames would be delayed at different rates. However, the explosions continued to animate in sync.

The Sprite_Animate function just updates the global variables frame and starttime to continue drawing each new frame with the Sprite_Draw_Frame function.

    //animate and draw the sprite
    for(int i = 0; i < 5; i++)
    {
        Sprite_Animate(frame, 0, 29, 1, starttime, rand() %100);
        Sprite_Draw_Frame(explosion, (i * 100), 100, frame, 128, 128, 6);
    }

There is a simple solution to this, and if anyone wants the full code I can send it to you by request.

Answer 1

SO i figured it out. The reason why they were all in sync even with random delay values is because they were all sharing the same global variables frame and starttime.

So instead, creating a structure of EXPLOSION with the member variables frame and starttime and than using a vector to contain them all. After it just had to be iterated through.

The new code is here in case someone else comes along this problem.

//The structue to contain each explosions own frame and starttime variables
struct EXPLOSION
{
    int frame;
    int starttime;
};


//============================================================================
//
// Function calls
//
//==============================================================================

//animate and draw the sprite
    for(int i = 0; i < 5; i++)
    {
        Sprite_Animate(explosions[i].frame, 0, 29, 1, explosions[i].starttime, rand() % 100);
        Sprite_Draw_Frame(explosion, i * 100, 100, explosions[i].frame, 128, 128, 6);
    }