/// <summary>
/// Ticks the kinematic property block forward by a certain delta time.
/// This will integrate all kinematic properties.
/// </summary>
static public Vector2 Integrate(ref KinematicState2D ioProperties, ref KinematicConfig2D inConfig, float inDeltaTime)
{
ApplyLimits(ref ioProperties, ref inConfig);
Vector2 offset = IntegratePosition(ref ioProperties, ref inConfig, inDeltaTime);
IntegrateVelocity(ref ioProperties, ref inConfig, inDeltaTime);
ApplyLimits(ref ioProperties, ref inConfig);
return(offset);
}
/// <summary>
/// Integrates position with velocity, acceleration, and gravity.
/// </summary>
static public Vector2 IntegratePosition(ref KinematicState2D ioProperties, ref KinematicConfig2D inConfig, float inDeltaTime)
{
float t2 = inDeltaTime * inDeltaTime;
float dx = (ioProperties.Velocity.x * inDeltaTime)
+ (((inConfig.Acceleration.x + inConfig.Gravity.x * ioProperties.GravityMultiplier) * t2 * 0.5f));
float dy = (ioProperties.Velocity.y * inDeltaTime)
+ (((inConfig.Acceleration.y + inConfig.Gravity.y * ioProperties.GravityMultiplier) * t2 * 0.5f));
return(new Vector2(dx, dy));
}
/// <summary>
/// Applies speed limits to the given property block.
/// </summary>
static public void ApplyLimits(ref KinematicState2D ioProperties, ref KinematicConfig2D inConfig)
{
float speed2 = ioProperties.Velocity.sqrMagnitude;
float high = inConfig.MaxSpeed;
float high2 = high * high;
float low2 = MinSpeed * MinSpeed;
if (speed2 < low2)
{
ioProperties.Velocity.x = ioProperties.Velocity.y = 0;
}
else if (high2 > 0 && speed2 > high2)
{
ioProperties.Velocity.Normalize();
ioProperties.Velocity.x *= high;
ioProperties.Velocity.y *= high;
}
}
/// <summary>
/// Integrates velocity, accounting for acceleration, gravity, friction, and drag.
/// </summary>
static public void IntegrateVelocity(ref KinematicState2D ioProperties, ref KinematicConfig2D inConfig, float inDeltaTime)
{
// acceleration
float x = ioProperties.Velocity.x + (inConfig.Acceleration.x + inConfig.Gravity.x * ioProperties.GravityMultiplier) * inDeltaTime;
float y = ioProperties.Velocity.y + (inConfig.Acceleration.y + inConfig.Gravity.y * ioProperties.GravityMultiplier) * inDeltaTime;
// friction
x = x < 0 ? Math.Min(x + inConfig.Friction.x * inDeltaTime, 0) : Math.Max(x - inConfig.Friction.x * inDeltaTime, 0);
y = y < 0 ? Math.Min(y + inConfig.Friction.y * inDeltaTime, 0) : Math.Max(y - inConfig.Friction.y * inDeltaTime, 0);
// drag
float drag = inConfig.Drag > 0 ? (float)Math.Exp(-inConfig.Drag * inDeltaTime) : 1;
x *= drag;
y *= drag;
// copy
ioProperties.Velocity.x = x;
ioProperties.Velocity.y = y;
}
