File channel node

Reads in channel and audio files for use by chops.

This CHOP reads in channel and audio files for use by CHOPs.

Valid Formats

The types of files that can be read into chops include:

`.chan`	Raw ascii channel files; a row of numbers per frame.
`.bchan`	Raw PRISMS/Houdini binary channel files.
`.clip .bclip`	Houdini native CHOP clip files.
`.bclipnc`	Houdini native non-commercial CHOP clip files.
`.chn .bchn`	Houdini channel segment files.
`.aif .aiff .aifc .au .sf .snd .wav`	Audio files.

The same files can be output from the menu on the CHOP tile by selecting Save Data Channels. For a complete listing of all valid formats for CHOPs, see the Formats section.

Other Input Devices

For Midi files (.mid or .midi), see the MIDI In CHOP. Some other input devices, (e.g. Puppetworks) can be read with the Pipe In CHOP.

Users can extend the file formats that are read/written by the File chop through the chop io and CLIPio files in $HFS/houdini. Use the clchan and clchn programs as examples of the input/output needed.

Parameters

File

Channel File

The name of the file to load. The button beside the string field brings up a file browser.

Name Options

Allows you to change the way the channels are named.

Use Names In File	Uses the channel names stored in the file. If the format does not support names (ie. sound files), then chan0, chan1, chan2, etc. is used.
Use New Names	The channel names are manually specified by the name parameter below.
Use Filename	The filename, minus the extension and path, is used. If more than 1 channel is in the file, the channels will be numbered to keep the names unique.

Name

The new name(s) of the file’s channels.

Rate Options

Allows you to change the sample rate of the file.

No Change	Use the file’s sample rate.
Override	Change the file’s sample rate to a new rate.
Resample	Change the file’s sample rate to a new rate and keep the time range constant.

Sample Rate

The new sample rate to use if Override or Resample is selected.

Extend Left

The extend condition before the channel’s beginning.

Extend Right

The extend condition after the channel’s ending.

Default Value

The value of the default value extend condition.

Common

Some of these parameters may not be avaiable on all CHOP nodes.

Scope

To determine which channels get affected, some CHOPs have a scope string. Patterns can be used in the scope, for example * (match all), and ? (match single character).

The following are examples of possible channel name matching options:

`chan2`	Matches a single channel name.
`chan3 tx ty tz`	Matches four channel names, separated by spaces.
`chan*`	Matches each channel that starts with `chan`.
`foot`	Matches each channel that has `foot` in it.
`t?`	The `?` matches a single character. `t?` matches two-character channels starting with t.
`r[xyz]`	Matches channels `rx`, `ry` and `rz`.
`blend[3-7:2]`	Matches number ranges giving `blend3`, `blend5`, and `blend7`.
`blend[2-3,5,13]`	Matches channels `blend2`, `blend3`, `blend5`, `blend13`.
`t[xyz]`	`[xyz]`matches three characters, giving channels `tx`, `ty` and `tz`.

Sample Rate Match

The Sample Rate Match Options handle cases where multiple input CHOPs’ sample rates are different.

Resample At First Input’s Rate	Use rate of first input to resample others.
Resample At Maximum Rate	Resample to highest sample rate.
Resample At Minimum Rate	Resample to the lowest sample rate.
Error if Rates Differ	Does not accept conflicting sample rates.

Units

The units for which time parameters are specified.

For example, you can specify the amount of time a lag should last for in seconds (default), frames (at the Houdini FPS), or samples (in the CHOP’s sample rate).

Note

When you change the Units parameter, it does not convert the existing parameters to the new units.

Time Slice

Time Slicing is a feature which boosts cooking performance and reduces memory usage. Traditionally, CHOPs calculate the channel over its entire frame range. If the channel does need to be evaluated every frame, then cooking the entire range of the channel is unnecessary. It is more efficient to calculate only the fraction of the channel that is needed. This fraction is known as a Time Slice.

Unload

Causes the memory consumed by a CHOP to be released after it is cooked and the data passed to the next CHOP.

Export Prefix

The Export prefix is prepended to CHOP channel names to determine where to export to.

For example, if the CHOP channel was named geo1:tx, and the prefix was /obj, the channel would be exported to /obj/geo1/tx.

Note

You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as obj:geo1:tx.

Graph Color

Every CHOP has this option. Each CHOP gets a default color assigned for display in the Graph port, but you can override the color in the Common page under Graph Color. There are 36 RGB color combinations in the Palette.

Graph Color Step

When the graph displays the animation curves and a CHOP has two or more channels, this defines the difference in color from one channel to the next, giving a rainbow spectrum of colors.

Usages in other examples

Example name	Example for