I newbe so... I understand that this is the place to post.. ( for now anyway ) I am writeing a 2D game (like that old Arc-Voley) and it involves a ball that gets up in the air... 1. How do I calculate the ball''s trajectory taking in acount gravitation and ball''s speed . For the movement of the ball I use iBallX and iBallY as coordinates and add or substract 1 to obtain somme offset. But could somme one show me a more good way to calculate the new iBallX and iBallY than ''+1'' and ''-1'' operations? ( sommething like angles, orientation vectors and staff like that ) 2. And second, if you some one can , a litle input on colisions detections in the same context( gravitation and speed ) ? I realy need your help , because I''dd realy like to make this in the right way .... so please "F1" me The Mask

You are going to need to give your ball a velocity. Use a struct to hold your ball data:

struct Ball{    float pos_x;    float pos_y;    float vel_x;    float vel_x;    float radius;}Ball ball; 

So you have position components (x and y) and velocity components (x and y) and a radius.

To make the ball go a certain direction, just modify it''s velocity. So let''s say you wanted to make it go at a 30 degree angle at 2 pixels per update:

angle = 6.283185 * 30.0 / 360.0;ball.vel_x = 2.0*cos(angle);ball.vel_y = 2.0*sin(angle); 

To move your ball according to it''s velocity, do this, once per game update:

ball.pos_x += ball.vel_x;ball.pos_y += ball.val_y; 

Also to make it act like gravity is pulling on it, do this once per update:

#define GRAVITY  (0.5)ball.vel_y += GRAVITY;  

You could use a const instead of a define. Also try values other than 0.5.

First I whant to apologise for that double thread I started.It may internet conection that gives me trouble. Sorry again.

Anon. Poster:
Thanks for the input. I had a similar struct but no radius.
And the number "6.283185" is, in fact 2*pi ? I think so , anyway may math formula is like that.
I''ll make the changes in my code to make rome for a radius.
But today I foud another problem .. "BltFast" wants integers or
long integers for the x, y parameters wich defines where to put my sprite. So? what I am going to do ? for now I converted the
parameteres to int " BltFast( (int) Player.dcurrX,
(int) Player.dcurrY, ...etc. )
Julio:
Thank you for your replay , and flipcode page is good stuff
much , very much to learn from that page....( I added to my favorites )

I am working very hard in this game but is dificult for me because is my second game in DX ( I made a very ugly tetris clone last week ).
So , I caunting on all of you to give me a help when needed
And sorry for my spelling, I am not so great at writeing in english ,( but I am working at that to )

Ok , so I managed to put some gravity in my game ( I am still adjusting it ) but now I am having problems with the player coliding with the ball .
I made a function that ( tries to ) manages ball vs player colisions and it has many if like
" if( ball.dCurrY + BALL_DIAMETER > player.dCurrY )
if ( ball.dCurrX +.... " well you get the ideea....
Well there are 2 problems :
- the function is not very elegant , ( lots cheks like
if(e < x+4 - and most importantly , the function works randomly. ( ratio 2 from 10 , I know , I know it is not very good )
The reason I post is mainly for the last problem: Can somebody tell me more about this colisions....?
I read what Julio sugested at flipcode.com , but there were more advanced thing (like 3D stuff ) and I didn''t understud much.

Hei, I''d realy need your help.....