public void DragIsProportionalToSpeed(Vector2 vel0, Vector2 vel1)
{
var forceCalculator = new VehicleForces(constants.Object);
var force0 = forceCalculator.GetDragForce(vel0);
var force1 = forceCalculator.GetDragForce(vel1);
Assert.True(force0.Length() < force1.Length());
}
public void DragIsZeroAtZeroVelocity()
{
var forceCalculator = new VehicleForces(constants.Object);
var vel = Vector2.Zero;
var force = forceCalculator.GetDragForce(vel);
Assert.True(force.Length() < float.Epsilon);
}
public void DragPointsInTheOppositeDirectionOfTheVelocityVector()
{
var forceCalculator = new VehicleForces(constants.Object);
var vel = new Vector2(0, 28);
var force = forceCalculator.GetDragForce(vel);
// NOTE(danielm): dot product of two units vectors is -1 if the
// angle between them is 180deg.
var dot = Vector2.Dot(Vector2.Normalize(force), Vector2.Normalize(vel));
var diff = Math.Abs(-1 - dot);
Assert.True(diff < float.Epsilon);
}