Box smooth fade

[rushensky]

When a player becomes invalid, the box fades out smoothly.

Not very useful function, but it looks nice

//  Expression
float Interp(float s1, float s2, float s3, float f1, float f3)
{
    if (s2 == s1)
            return f1;
    if (s2 == s3)
           return f3;
    if (s3 == s1)
           return f1;

    return f1 + ((s2 - s1) / (s3 - s1)) * (f3 - f1);
}

//  Where is the Player box

static DWORD smooth_time = 0;
 
// alpha
box_color[3] =  Interp((float)smooth_time, (float)GetTickCount(), (float)smooth_time + 300.f, box_color[3]  0);

// imgui
//box_color.Value.w = Interp((float)smooth_time, (float)GetTickCount(), (float)smooth_time + 300.f, box_color.Value.w, 0);