Global expression variables
Playbar variables
$FPS | Playback speed in frames per second (as set with the Playbar controls). |
$FSTART | Frame number of the first frame of animation (as set with the Playbar controls). $NFRAMES (the number of frames in the animation) = $FEND - $FSTART + 1. See also $RFSTART below. |
$FEND | Frame number of the last frame of animation (as set with the Playbar controls). See also $RFEND below. |
$F | The current frame, (as set with the Playbar controls). This is a very useful variable, especially for rendered picture filename numbering. |
$FF | Floating point frame number. |
$NFRAMES | Number of frames in the animation. $NFRAMES = $FEND (the last frame of animation) - $FSTART (the first frame of animation) + 1. |
$RFSTART | Frame number of the first frame shown in the playbar. The playbar can show a subset of the total number of frames, allowing you to focus on a particular section of a long animation. $RFSTART and $RFEND control the subset of frames shown in the playbar. |
$RFEND | Frame number of the last frame shown in the playbar. |
$T | Current time in seconds. Equals ($F-1)/$FPS |
$TLENGTH | Total length of animation in seconds. |
$TSTART | Start time of animation in seconds. |
$TEND | End time of animation in seconds. |
Global Variables
$PI | The mathematical constant pi (3.1415926…). You can use it to calculate the lengths of arcs. 2*$PI*r (radius of circle) equals the circumference. Also, pi = 180˚ expressed in radians. |
$E | The mathematical constant e (2.71828…). |
$HIP | Job directory. This defaults to the directory where you started Houdini. You can set it through the Textport. |
$HIPNAME | The name of the current .hip file. |
$ACTIVETAKE | Contains the name of the current take. |
Channel Variables
$OS | Operator String. Contains the current OP’s name. |
$CH | Current channel name. |
$IV | In value (value at start of segment). |
$OV | Out value. |
$IM | In slope |
$OM | Out slope |
$IA | In acceleration |
$OA | Out acceleration |
$LT | Local time - not including stretch or offset |
$IT | Start time of segment |
$OT | End time of segment |
$LIT | Local start time of segment |
$LOT | Local end time of segment |
$PREV_IT | Previous segment start time |
$NEXT_OT | Next segment end time |
COP-specific variables
$CSTART | Start frame of the current COP. |
$CEND | End frame of the current COP. |
$CFRAMES | Number of frames for the current COP. |
$CFRAMES_IN | Number of frames available from the first input COP. |
$CINC | Gets the global frame increment value. |
$W | Current image width. |
$H | Current image height |
Output Driver Specific Variables
$N | Current frame being rendered. |
$NRENDER | Number of frames being rendered. |