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This generator CHOP generates channels for bone objects based on a bone chain and an end affector. It can solve for the bone angles using a variety of different solver types.
Specifies the solver to use to generate the channels.
No solver. Use the original parameter values.
Show Rest Position
No solver. Uses the rest angles.
Show Capture Position
No solver. Uses capture angles.
Uses IK solver. The solution is uniquely defined by the end affector position. Constraint parameters are ignored.
IK With Constraints
Uses a modified IK solver. The solution depends on the previous solution. Constraint parameters are used to limit the range of motion.
The bones are positioned to follow the specified curve as closely as possible.
This is the first bone in the chain for which this CHOP should create solution channels.
This is the last bone in the chain for which this CHOP should create solution channels.
For Inverse Kinematics and IK With Constraints solvers, this is the object to use as the end affector when solving for the bone angles.
For the Inverse Kinematics solver, this specifies an object that controls the twist orientation of the solution bone angles.
For the Inverse Kinematics solver, this parameter specifies an additional twist angle to be applied to the solution bone angles.
For the Inverse Kinematics solver, this parameter represents how easily the End Bone can be pulled off the End Affector as the bone chain is stretched out.
For the Follow Curve solver, this parameter specifies the object that contains the curve geometry that the bone chain should follow.
For the Follow Curve solver, this parameter specifies how the curve normals should be transferred to the bone chain. Note that the normals are interpolated on the curve between the curve breakpoints. Because breakpoints (and not control points) lie on the curve it is more meaningful to use interpolate the breakpoint rather than the control vertex values. Though, breakpoint normals are calculated from the control vertices.
The bone chain normals approximate the curve normals as much as the curve parameters allow. (Path parameters, for example, carry extra information that allow twists of more than 360 degrees)
The bone chain maintains its own normals defined by the rest position.
The bone chain normals interpolate the curve normals using quaternion rotation of the vectors. (i.e., the bone chain normals lie on the shortest arc defined by two curve normals on a unit sphere.
The bone chain normals are calculated using twist angles around the curve (between the curve points at which a normal is defined). The angle difference is restricted to the interval between -180 to 180 degrees.
The bone chain normals are calculated using twist angles. This option is similar to Clamped Angles, except the twist angles around the curve are not restricted. Note, that for this option, the curve must carry additional information (see Object Path Tool). Otherwise, this option is downgraded to Clamped Angle.
This option blends between the local bone rotation values
and the solved solution. When this value is
0 it produces
the local bone rotation values and when it is
1, it produces
the solved bone rotation values.
When this checkbox is turned on, the bone chain will completely straighten out in the direction of the goal if the IK goal is farther away than the length of the bone chain (with a tolerance of the tracking threshold). If this checkbox is turned off, no attempt is made to further straighten the IK solution. By default it is turned off because it is faster.
Tracking Threshold Factor
This value specifies the accuracy threshold for Inverse Kinematic solutions. Use smaller values for more accurate solutions at the expense of more computation time. Use larger values to save computation time at the expense of getting less accurate solutions.
Only create one-sample channels, at the Start position.
When not in Single Frame mode, the CHOP can use the previous rotation values as a hint when generating the next frame’s rotation values.
The start position of the CHOP.
The end position of the CHOP.
The sample rate of the CHOP.
The left extend condition (before the CHOP’s start).
The right extend condition (after the CHOP’s end).
The value to use for the "Default Value" extend condition type.
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.