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The Export CHOP is a convenient tool for exporting channels. It allows you to match a CHOP’s channels with different destination channels, without needing to rename the channels. It also provides an enable input to turn exporting on or off on a frame by frame basis.
The first input contains the channels to export.
The second input should contain one channel. This channel controls the exporting of the channels in the first input; if it is 1 at a frame, the channels will be exported for that frame, if it is 0, they will not be exported.
The export flag must be turned on for this node to be active. It is off by default.
The list of source channels. Not all channels need to be listed (unlisted channels will not be exported). The order these channels are listed is important; they will be matched to the paths in the Path parameter in the same order.
This is the path to the node(s) to export to. It is concatenated with the Path field to form the complete path to the channel to override.
For example, if Node is “/obj/model” and Path is “tx”, the channel “/obj/model/tx” will be overridden. The resulting path will be globbed, so a Node of “/obj/*” and Path of “tx” will match any channel named tx in any node inside
The list of destination channels. If there are more destination channels than source channels, export will loop back through the source channels until all destination channels have been matched.
If turned off, then exports of this node will be inactive. The export connection will still exist but not be active.
Some of these parameters may not be available on all CHOP nodes.
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:
Matches a single channel name.
chan3 tx ty tz
Matches four channel names, separated by spaces.
Matches each channel that starts with
Matches each channel that has
foot in it.
? matches a single character.
t? matches two-character channels starting with t.
Matches number ranges giving
[xyz]matches three characters, giving channels
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.
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).
When you change the Units parameter, it does not convert the existing parameters to the new units.
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.
Causes the memory consumed by a CHOP to be released after it is cooked and the data passed to the next CHOP.
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
You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as
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.
This is an example of the Export CHOP. The Export CHOP is a convenient tool for exporting channels. It allows you to match a CHOP’s channels with different destination channels, without needing to rename the channels. This demonstrates a method to export channels from CHOPs to the ty parameter of a model.