Controlling OPs with CHOPs

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Channel Operators (CHOPs) have a wide range of uses in TouchDesigner, and one of the most common is controlling the parameters of other operators. This allows us to use CHOPs to drive animation of parameters of operators. We might use this to control parameters like opacity, scale, or position. A best practice when working with CHOPs is to end your network with a Null CHOP. Null operators allow us to continue to make changes in our operator network without needing to re-write our expressions or re-export our CHOP channels.

Another Channel Operator you can use to see the history of any CHOP is the Trail CHOP. By connecting a Trail CHOP to a single sample CHOP you can better see the range and time-history of a CHOP’s output. The Trail CHOP’s display is a window of time where the far right side of the operator’s viewer is the value at the current frame. You can increase or decrease the amount of time displayed by changing the Trail CHOP’s Window Length parameter.

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