Attribute	Type	@	$	Description	Category
Position	Vector	@P		Position of element.	Geometry
Normal	Vector	@N		Normal vector of the element.	Geometry
Color Diffuse	Vector	@Cd		Color diffuse using RGB values for the vector.	Geometry
Scale (Uniform)	Float	@pscale		Uniform scale of element.	Points
Scale (Non-uniform)	Vector	@scale		Non-uniform scale with each float representing each axis: x, y, z.	Points
Orient	Quaternion	@orient		Orientation of the element. This takes precedence over @N if both @N and @orient exist in element. But if @orient does not exist in element, then @N defines its orientation along Z-axis. Since @N is simply a vector and @orient is a quaternion, then @orient has greater precision, and therefore precedence.	Points
Id	Integer	@id		Unique value identifying an element, such as a particle. Even after it dies, another element or particle will not acquire that id value.	Particles
Age	Float	@age		Denotes the time that the particle has been in existence since spawning, or being born, from its origin. Value is in seconds and typ. noted as fractions per the frame rate.	Particles
Life	Float	@life		Number of seconds that the particles are expected to live. Defined in the POP Source.	Particles
Age / Life	Float	@nage		Unlike @age, which is just a recording of time that the particle has been alive, @nage is a percentage of how long it has been alive relative to its @life. It is an implicit value denoting @age / @life.	Particles
Dead	Integer	@dead		An attribute to mark particles that have @age > @life.	Particles
Acceleration	Vector	@accel		Can be calculated via Trail SOP set to Compute Velocity and Compute Acceleration.	Particles