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DontPanic

SDL input player movement problem

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I have a set up much like the second example in this tutorial: http://gpwiki.org/index.php/SDL:Tutorials:Practical_Keyboard_Input However I wish so that when moving in a diagonal it doesn't simple move the player say left and up by the same velocity units as that would mean moving at a diagonal moves you faster. So I have this little bit of code: float diagonal = m_MovementSpeed -(0.70710678118654752440084436210485 * m_MovementSpeed); It in effect is performing what trig would since the player only moves 8 directions. However on trying to implement this diagonal movement velocity change my code has become an almighty mess. It's a horrific mess of bools and if statements across the key down and key up events. It works to a point but it fails when I have 3 movement keys pressed. Can anybody come up with a cleaner and bug free method of implementing it? That means movement is always what it is meant to happen. For example say left, down and right are pressed then the player should move down m_MovementSpeed and then if right is released you go diagonal at the reduced velocity of x and y. Oh and to complicate matters in the game you can control either of 2 characters. If you hold a key (currently m for no reason) you move one of them and if you release it you move the other. They are separate objects (OO) and because of their relationship one is a data member of the other. That is currently controlled by a bool in both objects, and on input both bools are changed to represent whether they are being controlled or not. I've got myself in a muddle over this. Guess it's simple and I just need to come back to it later but it's bothering me. I'm sure you know the feeling.

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xvel = 0; yvel = 0;
if(left key down)
xvel +1
if(right key down)
xvel - 1
if up key down
yvel +1
if down key down
yvel -1

normalize vel vector.

As a quick idea any way, just figure out the direction then normalize the vector.

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The problem is that it doesn't account for the different velocity when moving diagonally. For instance:

if(m_dirUp == true && m_dirRight == true)
{
m_VelY += diagonal;
m_VelX -= diagonal;
}

So to then cancel that out doesn't work. where velocity is normally 2 it would happen that moving up/right diagonally and then releasing right would make x velocity:

x velocity = 1.42 - 2

So I have accounted for that with more if's and bool variables. Every time I do that I find that something doesn't work and I add more. So the solution is to have a very long list of if statements working out exactly what is pressed at any given time and what was released and performing the correct changes to the velocities. However that is already ugly, hence why I'm wondering if anyone else has a solution. I'm hoping I'm not the only person who has this setup and wants too have 8 way movement that is fairly accurate compared too diagonals moving faster.

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Quote:
Original post by DontPanic
The problem is that it doesn't account for the different velocity when moving diagonally.


It does: that's what normalising the vector means.

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