This CHOP takes input from one chop, uses the designated channels in calculation, and outputs transform channels.
It is recommended not to input initial rotations on the objects when using this feature (translation works fine, however).
This CHOP provides two transform modes (they are mainly for cameras):
The fixed mode fixes the object (camera) in a plane (which should ideally be parallel to the XZ plane)
The free mode allows the object (camera) to move in the lookat direction.
For both modes, no tilt will be introduced as this is not desired for first-person cameras.
The Device Transform and Gamepad CHOPs can be used together to drive objects (like the camera object) in a “First-Person” way.
The fixed mode fixes the object in a plane which should be parallel to the XZ plane. The free mode allows the object to move in the lookat direction
Customize the translation speed. Default is 1 and range is 0-1000
Customize the rotation speed. Default is 5 and range is 0-20.
A button to set all outputs of the CHOP (except scale) to 0, essentially resetting the transform.
Back & Forth
Specify the name of the channel whose data will be used to move back & forth. Default is left stick y axis. Axis input expected. Positive is going forth.
Negate the input channel before using it (for instance, from a to -a).
Left & Right
Specify the name of the channel whose data will be used to move left & right. Default is left stick x axis. Axis input expected. Positive is going right.
Look Up & Down
Specify the name of the channel whose data will be used to look up & down. Default is right stick y axis. Axis input expected. Positive is looking up.
Look Left & Right
Specify the name of the channel whose data will be used to look left and right. Default is right stick y axis. Axis input expected. Positive is looking right.
ty directly regardless of current rotation. Default is right bumper. Axis or button inputs accepted.
ty directly regardless of current rotation. Default is left bumper Axis or button inputs accepted.
Temporarily increases translation speed by a multiplier of 1 to 10 according to input given. Default is right trigger. Axis or button inputs accepted.
Temporarily increases translation speed by a multiplier of 1 to 10 according to input given. Default is left trigger. Axis or button inputs accepted.
The alignment option to use.
Extend to Min/Max
Find the earliest start and latest end, and extend all inputs to that range using the extend conditions.
Stretch to Min/Max
Find the earliest start and latest end, and stretch every channel’s start and end to that range.
Shift to Minimum
Find the earliest start and shift all channels so they all start at that index. All channels are extended to the length of the longest one.
Shift to Maximum
Find the latest end and shift all channels so they all end at that index. Extend all channels to the length of the longest one.
Shift to First Interval
Shift all channels to the start of the first channel and sample all inputs using the first input’s range.
Trim to First Interval
Trim all channels to first channel’s range.
Stretch to First Interval
Stretch all channels to the first channel’s range.
Trim to Smallest Interval
Trim all channels to the smallest start/end interval. The start and end values may not come from the same channel.
Stretch to Smallest Interval
Stretch all channels to the smallest start/end interval. The start and end values may not come from the same channel.
Specifies the range of data to generate.
Use Full Animation Range
All of the animated range.
Use Current Frame
Only the sample at the current frame.
The range is specified from the Start and End parameters.
Use Value Animation
The range is taken from range of keys available in the evaluated Value parameters.
The start time of the channel range.
The end time of the channel range.
The sample rate of the CHOP.
Number of Threads
The number of separate threads to use to evaluate the channel samples. The default is no threading.
Since Houdini evaluates the VEX program for each sample in the input geometry, it can benefit greatly from threading on a multi-processor or multi-core machine when the CHOP nodes have many samples.
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.