public GroundCollisionConstraint(ParticleSystem particleSystem, Particle particle, float terrainHeight)
			: this(particleSystem, particle, terrainHeight, 1)
		{

		}
		public GroundCollisionConstraint(ParticleSystem particleSystem, Particle particle, float terrainHeight, float stiffness)
			: base(particleSystem, stiffness)
		{
			_particle = particle;
			_terrainHeight = terrainHeight;
		}
		public SphereCollisionConstraint(ParticleSystem particleSystem, Particle particle, BoundingSphere boundingSphere)
			: this(particleSystem, particle, boundingSphere, 1)
		{

		}
		public Constraint(ParticleSystem particleSystem, float stiffness)
		{
			_particleSystem = particleSystem;
			Stiffness = stiffness;
		}
		public SphereCollisionConstraint(ParticleSystem particleSystem, Particle particle, BoundingSphere boundingSphere, float stiffness)
			: base(particleSystem, stiffness)
		{
			_particle = particle;
			_boundingSphere = boundingSphere;
		}