public void ModifyDirection( ref Vector3F direction, Block currentBlock )
{
double t = 1.0 / ( ProcessingStepsPerSecond * MovesPerProcessingStep );
Vector3F v = direction * ( ProcessingStepsPerSecond * MovesPerProcessingStep );
Vector3F dv = new Vector3F( 0, 0, ( float )( -G * t ) );
direction = ( v + dv ).Normalize();
}