Inverse Curve CHOP
The Inverse Curve CHOP calculates an inverse kinematics simulation for bone objects using a curve object.
The Inverse Curve CHOP will stretch and position a set of bones to follow a curve defined by another set of objects (guide).
Specify the first and last bone in the chain with Bone Start / Bone End.
Specify the Guide by listing them in order, space separated, in the Guide Components field. This parameter also accepts patterns and wildcards. Example:
null[1-5] null17 null4. You can also specify bones in this group as well.
The CHOP will then create a set of rotate and bone-length channels for each bone. Additionally, the CHOP will also output 3 translate channels for the first bone in the chain. It will also setup the export links automatically, so you just have to turn on the export flag for this CHOP.
The way the CHOP solves this system is by creating a guide curve between the supplied Guide objects. Use the Interpolation and Order parameters to define what type of curve it will use. By default, the control vertices of the curve will be the centroids of the object. The curve is also given orientation, by adopting the orientation of each guide object. The bones line up their X axes with this orientation.
You can view this curve by using the Inverse Curve SOP. Just supply it with the name of the Inverse Curve CHOP and it will extract the geometry for viewing/debugging purposes. It actually will contain 3 curves (the original guide, and the guide displaced in +X and +Y). These curves can be skinned with a Skin SOP for better feedback, etc.
The span parameters can be used to trim out the beginning and end of the guide curve if so needed. For example Span 0.3 0.7 will lay the bones along the middle 40% of the curve.
In the rare case that the user has setup a curve with all the X axes (twists) pointing along the same direction of the curve, then the Up Vector parameter is used to break the tie, so to speak. However, this curve setup is likely degenerate to start with and should be avoided by twisting all the objects 90 degrees.
Parameters - Inverse Curve Page
span- ⊞ -
interpolation - ⊞ -
- Polygonal Curve
- Bezier Curve
- NURBS Curve
upvector- ⊞ -
Parameters - Common Page
timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.
scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.
Sample Rate Match
srselect - ⊞ - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.
- Resample At First Input's Rate
first- Use rate of first input to resample others.
- Resample At Maximum Rate
max- Resample to the highest sample rate.
- Resample At Minimum Rate
min- Resample to the lowest sample rate.
- Error If Rates Differ
err- Doesn't accept conflicting sample rates.
exportmethod - ⊞ - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.
- DAT Table by Index
datindex- Uses the docked DAT table and references the channel via the index of the channel in the CHOP.
- DAT Table by Name
datname- Uses the docked DAT table and references the channel via the name of the channel in the CHOP.
- Channel Name is Path:Parameter
autoname- The channel is the full destination of where to export to, such has
autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.
exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).
|• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •|
An which operate on (a series of numbers) which are used for animation, audio, mathematics, simulation, logic, UI construction, and many other applications.
A Time Slice is the time from the last cook frame to the current cook frame. In CHOPs it is the set of short channels that only contain the CHOP channels' samples between the last and the current cook frame.
A parameter in most CHOPs that restricts which channels of that CHOP will be affected. Normally all channels of a CHOP are affected by the operator.
samples-per-second of a CHOP. Each CHOP in your network has a sample rate, whether it is used or not. The overall timeline has a "frame rate", which is the number of animation frames per second, generally your monitor display frequency.
Exporting is the connection of CHOP channels to parameters of operators. The output of each exporting CHOP is one or more channels, active only while the is on. The current value of a channel can be exported to a parameter of any operator, overriding that parameter's value. See .
An that manipulates text strings: multi-line text or tables. Multi-line text is often a command , but can be any multi-line text. are rows and columns of cells, each containing a text string.
The location of an operator within the TouchDesigner environment, for example,
/geo1/torus1, a node called
torus1 in a component called
geo1. The path
/ is called . To refer instead to a filesystem folder, directory, disk file or
http: address, see .
Parameters in TouchDesigner are an operator's settings (numbers, menus, flags, strings, paths) which the user can alter. Parameters for any operator can be opened by right-clicking on the operator and selecting "Parameters..." A currently selected operator's parameters can be viewed in a by pressing the keyboard shortcut 'p'.
TouchDesigner is a hierarchy of components. "root" is the top-most network in the hierarchy. The is simply
/. A typical path is