[SDL] Speed In Games

Ryan Wahle wahle at ryu.addell.com
Sun Aug 29 23:38:37 PDT 1999


I have never used the SDL_GetTicks... Could you explain that alittle more?

Thanks

On Mon, 30 Aug 1999, Karsten-Olaf Laux wrote:

> on Mon, 30 Aug 1999 Ryan Wahle wrote:
> >Hi, does anyone know of a way to control the speed at which an object
> >moved. I can do the x++ and the y++ but after a x and y = 3 it's just way
> >to fast to play....
> >
> >does anyone have any ideas to implement this?
> >
> >thanks.
> 
> Hi,
>  
> what about the following:
> <<<<<<<<<<<<<<<<<<<<<
> 
> float vx = 0.001;     // the horizontal speed component in pixels / ms
> float vy = 0.0005;   // the horizontal speed component in pixels / ms
> 
> unsigned int x,y;    // the position in pixels
> 
> unsigned int delta_t;  // time since last position update in ms  
> 		      //(... SDL_GetTicks())
> 
> ...
> x += (unsigned int)(vx * delta_t + 0.5);
> y += (unsigned int)(vy * delta_t + 0.5);
> >>>>>>>>>>>>>>>>>>>>>
> 
> ok, it uses floating point arithmetics, which might be replaced by fixed point
> arithmetics.
> 
> the +0.5 converts float to integer more precisely. (as long as the values > 0)
> 
> 
> regards,
> 
> --
> Karsten-O. Laux           
> klaux at student.uni-kl.de
> http://www.rhrk.uni-kl.de/~klaux
> 




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