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The Fetch CHOP imports channels from other OPs. It can grab either the regular control channels from any OP, or data channels that are output from chops. Control channels are those channels associated with parameters of any OP. Data channels are only present in CHOPs, and are the channels output by CHOPs.
The Fetch CHOP can get the output channels from CHOPs in other CHOP networks.
The Channels field also supports channel groups with the syntax.
Fetching cannot be recursive. If a CHOP exports to an object’s channel, and that object channel is fetched, the Fetch CHOP cannot feed to the CHOP that exports. This will produce an error message in the Fetch CHOP. If this occurs, you will have to lock the Fetch CHOP before exporting back to the object.
The Node and Channels determine where the channels come from. They are concatenated together, so a channels of "tx" and a path of "/obj/model" will fetch "/obj/model/tx". They also accept globbing, so a Node of /obj/ and a channel of tx would select all the tx channels from all the nodes inside.
This field is appended to the specified Node to complete the path. Wildcards and multiple entries are allowed. t? implies all translate channels, tx, ty, tz. Alternately, you can set leave the node blank and specify the full path in Channels, such as /obj/geo/*.
If fetching from another CHOP, you can fetch its OP Control Channels or CHOP Data Channels. All other OPs have only Control Channels, so leave this menu set at "OP Control Channels".
Fetched channels can be eliminated to include only control channels that have been added, or further, channels that have been added and are animating over the start/end time range. Applies to OP Control Channels.
Sets how the fetched channels are named. A : is placed in the channel name where / is in the path.
Only use the name of the channel.
OP and Channel Names
Include the parent OP name with the channel name, separated by a colon (:).
Full Path Name
Use the full path as the name, with the parts separated by a colon (:).
Indicates how much of the channel to fetch.
Use Full Animation Range
All of the animated range.
Use Current Frame
Only the sample at the current frame.
Specify the range below.
The beginning of the fetch.
The end of the fetch.
Determines the sample rate to be used.
New Rate (Same Index Range)
Resample to new rate below.
Resample From Maximum Rate
Use the highest rate found.
Resample From Minimum Rate
Use the lowest rate found.
The sample to use if "New Rate" is selected, or if no rates are found.
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 Fetch CHOP. Here the Fetch CHOP is used to import the tx, ty and tz channels from a null node.
The following examples include this node.