// Available in all SOP wrangles f@Frame //The current floating frame number, equivalent to the $FF Hscript variable f@Time //The current time in seconds, equivalent to the $T Hscript variable i@SimFrame //The integer simulation timestep number ($SF), only present in DOP contexts. f@SimTime //The simulation time in seconds ($ST), only present in DOP contexts. f@TimeInc //The timestep currently being used for simulation or playback.// Available in Attribute Wrangle (point, vertex, primitive and detail) v@P //The position of the current element. i@ptnum //The point number attached to the currently processed element. i@vtxnum //The linear number of the currently processed vertex. i@primnum //The primitive number attached to the currently processed element. i@elemnum //The index number of the currently processed element. i@numpt //The total number of points in the geometry. i@numvtx //The number of vertices in the primitive of the currently processed element. i@numprim //The total number of primitives in the geometry. i@numelem //The total number of elements being processed.// Available in Volume Wrangle v@P //The position of the current voxel. f@density //The value of the density field at the current voxel location. v@center //The center of the current volume. v@dPdx, v@dPdy, v@dPdz //These vectors store the change in P that occurs in the x, y, and z voxel indices. i@ix, i@iy, i@iz //Voxel indices. For dense volumes (non-VDB) these range from 0 to resolution-1. i@resx, i@resy, i@resz //The resolution of the current volume.

// Int @id // A unique number that remains the same throughout a simulation.// Float @pscale // Particle radius size. Uniform scale. Set display particles as 'Discs' to visualize. @width // Thickness of curves. Enable 'Shade Open Curves In Viewport' on the object node to visualize. @Alpha // Alpha transparency override. The viewport uses this to set the alpha of OpenGL geometry. @Pw // Spline weight.// Vector3 @P // Point position. Used this to lay out points in 3D space. @Cd // Diffuse color override. The viewport uses this to color OpenGL geometry. @N // Surface or curve normal. Houdini will compute the normal if this attribute does not exist. @scale // Vector scale. Allows directional scaling or stretching (in one direction). @rest // Used by procedural patterns and textures to stick on deforming and animated surfaces. @up // Up vector. The up direction for local space, typically (0, 1, 0). @uv // UV texture coordinates for this point/vertex. @v // Point velocity. The direction and speed of movement in units per second.// Vector4 @orient // The local orientation of the point (represented as a quaternion). @rot // Additional rotation to be applied after orient, N, and up attributes.// String @name // A unique name identifying which primitives belong to which piece. Also used to label volumes. @instance // Path of an object node to be instanced at render time.

float f@name // Floating point scalar values. vector2 u@name // Two floating point values. Could be used to store 2D positions. vector3 v@name // Three floating point values. Usually positions, directions, normals, UVW or colors. vector4 p@name // Four floating point values. Usually rotation quaternions, or color and alpha (RGBA).int i@name // Integer values (VEX uses 32 bit integers). matrix2 2@name // Four floating point values representing a 2D rotation matrix. matrix3 3@name // Nine floating point values representing a 3D rotation matrix or 2D transform matrix. matrix 4@name // Sixteen floating point values representing a 3D transform matrix.string s@name // A string of characters.

ch("flt1"); // Float parameter chf("flt2"); // Float parameter chi("int"); // Integer parameter chv("vecparm"); // Vector3 parameter chp("quat"); // Quaternion (Vector4) parameter ch3("m3"); // 3×3 matrix parameter ch4("m4"); // 4×4 matrix parameter chs("str"); // String parameter chramp("r", x); // Spline ramp parameter vector(chramp("c", x)); // RGB ramp parameter

f@age // Time in seconds since the particle was born. f@life // Time in seconds the particle is allowed to live. When f@age>f@life, i@dead will be set to 1. f@nage // Normalized age, f@age divided by f@life. Implicit attribute, you cannot write to this. i@dead // Whether a particle is living (0) or dead (1). A dead particle is deleted in the Reaping stage. i@id // A unique id for the particle that remains the same throughout a single simulation. i@stopped // Whether a particle is moving (0) or stopped (1). i@stuck // Whether a particle is free (0) or stuck (1). i@sliding // Whether a particle is free (0) or sliding along a surface (1). f@cling // Force applied to sliding particles inwards (according to the collision's surface normal). s@pospath // The path to the object that the particle is colliding with. i@posprim // Which collision primitive in the path geometry whose position we wish to refer to. v@posuv // Parametric uv on the collision primitive. i@hittotal // The cumulative total of all hits for the particle (only incremented once per timestep). i@has_pprevious // This is set to 1 if v@pprevious contains valid values. v@pprevious // Stores the position of the particle on the previous frame. Used for collision detection. i@hitnum // The number of times the particle collided in the last POP Collision Detect. s@hitpath // The path to the object that was hit. A path to a file on disk or an op: path. i@hitprim // The primitive hit. Could be -1 if it the collision detector couldn’t figure out which prim. v@hituv // The parametric UV space on the primitive. v@hitpos // Where the hit actually occurred. Useful if the colliding object was moving. v@hitnml // The normal of the surface at the time of the collision. v@hitv // The velocity of the surface at the time of the collision. f@hittime // When the collision occurred, that could be within a frame. f@hitimpulse// Records how much of an impulse was needed for the collision resolution. varies with timestep. f@bounce // When particles bounce off another object, this controls how much energy they keep. f@bounceforward // Controls how much energy they keep in the tangential direction. f@friction // When particles bounce, they are slowed down proportional to how hard they hit. s@collisionignore // Objects that match this pattern will not be collided. f@force // Forces on the particle for this frame. f@mass // Inertia of the particle. v@spinshape // This is multiplied by f@pscale to determine the shape of the particle for rotational inertia. f@drag // How much the particle is effected by any wind effects. f@dragexp // Ranges from 1 to 2, default is set on the solver. Used for both angular and linear drag. v@dragshape // How much the particle is dragged in each of its local axes. v@dragcenter// If specified, drag forces will also generate torques on the particle. v@targetv // The local wind speed. Thought of as the goal, or target, velocity for the particle. f@airresist // How important it is to match the wind speed. Thickness of the air. f@speedmin // Minimum speed, in units per second, that a particle can move. f@speedmax // Maximum speed, in units per second, that a particle can move. p@orient // Orientation of the particle. Used for figuring out 'local' forces. v@w // Angular speed of the particle. A vector giving the rotation axis. v@torque // The equivalent of force for spins. No inertial tensor (the equivalent of mass) is supported. v@targetw // The goal spin direction and speed for this particle. f@spinresist// How important it is to match the targetw. f@spinmin // Minimum speed in radians per second that a particle can spin. f@spinmax // Maximum speed in radians per second that a particle can spin.