Hey guys, i have a problem with my game and i need help...

this void since not working... any one can fixe this?

       private void GravidadeNomal()
        {
            if ((Caixa.Aceleração.Y != 1) && (G == true))
            {
                Vector2 g = Gravidade / 10;
                Caixa.Aceleração += g;
            }
        }

PSs:
       "Caixa" is one textured box thats appear on the screen
       "Aceleração" is a Vector2D
       "Gravidade" is a Vector2D Gravidade = new Vector2D(0, 10)

Is the problem that the code doesn't compile? If so, what is the error?
Is the problem that the code compiles and runs, but doesn't do what you think it should?
If so, what do you think it should do? And what is it doing? (Have you put a breakpoint in there and stepped through it?)

In my game, the box ("Caixa") have to be drawed on the scren whit acceleration ("Aceleração")!

Than the new value of Caixa.Aceleração will plus whit Caixa.Velocidade (Velocity)...

And finale, Caixa.Velocidade will plus whit Caixa.Posição (Position)... To be Draw on the Screen!

But the box initialize and stay in there original position ("Caixa.Posição")...

Please... Any one help!

PSs: This is the basic of the code ( realy simple )


CaixaNormal.cs

One thing that stands out is that you are comparing Tempo to 0.100 using the '==' operator.

Generally, you don't want to compare floating point numbers with the equality operator, since because of floating point errors things will never be exactly a particular value.  I suspect that if you put a breakpoint in your velocity/position calculations you will find that code is never executed.

So instead you might want to do:
if (Tempo > 0.100)
{
    Tempo -= 0.100;

    // do your velocity, position calculations, etc....
}


You also have the same problem in GravidadeNomal.  The "((Caixa.Aceleração.Y != 1)" will almost always be true.  I'm not sure if that's what you want.

Ok, I done this changes, but anything changes!

Thanks very much for the tip, mtnPhil, but i will rewrite my code and make this works.

Thanks, again.

Another problem is that you are using this:

GameTime Milisegundo = new GameTime(); 

But I don't ever see where the Milisegundo value is changed.  So the EllapsedGameTime will always be zero.

You should instead be using the GameTime object passed to the Update method.

GameTime Milisegundo do not change! It's always 0.001...

This variable is used in Básico(), so it's used in the Update method. ( if you had not seen )

"GameTime" is just a value type, like a "float" or a "Vector3." It will not change unless you assign a new value. That's why Update() passes in a new GameTime value for you. You can assign the GameTime passed into Update() to your Milisegundo member to make it change.

jwatte:

"GameTime" is just a value type, like a "float" or a "Vector3."

A minor nit pickingly correction to a mistake I made before, too: Apparently GameTime is a reference type, not a value type. Only the TimeSpans it defines are value types.

But... Tempo += Milisegundo.ElapsedGameTime.Milliseconds; ... do not means Tempo += 0.001    ?

PS: I already try put just this code... Tempo += 0.001 ... but nothing changes.

"Tempo" is a double

You need to get friendly with your debugger. Put some breakpoints in your code and/or single-step through the functions in question. By seeing the flow of execution and examining your variables at each step, you should be able to easily tell what is going wrong.

As for the Milisegundo variable, you should just pass the gameTime parameter from your Update method into any other method that needs access to game time. Your Milisegundo variable will not work as you are expecting it to.

Milliseconds is guaranteed to not work with your code, because it returns an integer.  So, every value after that addition is going to be greater than 1.  TotalMilliseconds would be more appropriate, but still not correct.  With your usage, you want TotalSeconds. 

Tempo += 0.001 is also likely to not work due to representation errors.  As stated before, there is rarely a good reason to use == with floating point comparisons.  Try changing your code to something like this:

Two other issues that I see are the previously mentioned issue with GameTime and an issue with your gravity function.

First, the Milisegundo is only initialized with a new GameTime() call.  That should set it to all zeros.  It never gets updated in the code you have posted.  I don't know if you ever changed that.  So, it always being adding zero time.  You want to update it in the update function with:


Ideally, you wouldn't even do this and you would just pass the GameTime variable into your functions.  Or what I do, is to pull out the time variable that I'm interested in (TotalSeconds) and just pass that to my functions.

The other issue has to do with your gravity function and it may not be an issue at all.  Assuming that no rounding errors occur in the math of the first call of GravidadeNormal(), then Caixa.Aceleração is going to have a Y value of 1.0f.  So, the acceleration value is going to change once and then your if statement will prevent further changes.  That might be what you want, but it is a poor way of going about it, imo.

Oh! Realy thank you for the help, i got it!

One more question... What the diference between this:


and this:


                ??

"&&" is the logical AND operator, meaing "if this is true AND that is true". "&" is the bitwise AND operator. For more information on bitwise operators in C#, see this article.

Also, in the context of booleans & means that both operands are always evaluated, while && allows for short-circuit evaluation