Entry Point

All communication between After Effects and an effect plug-in is initiated by After Effects, and it all happens by the host (After Effects) calling a single entry point function.

For all effect plug-ins, the entry point function must have the following signature:

PF_Err main (
  PF_Cmd       cmd,
  PF_InData    *in_data,
  PF_OutData   *out_data,
  PF_ParamDef  *params[],
  PF_LayerDef  *output,
  void         *extra)

The name of the entry point function above is “main”, but it can be whatever is specified in PiPL Resources.

Before each call to the entry point function, After Effects updates PF_InData and the plug- in’s parameter array PF_ParamDef[] (except as noted).

After the plug-in returns from its call, After Effects checks PF_OutData for changes and, when appropriate, uses the PF_LayerDef the effect has rendered.

Entry Point Function Parameters

Argument Purpose
cmd After Effects sets the Command Selectors to tell the plug-in what to do.

Information about the application’s state and the data the plug-in is being told to act upon.

Pointers to numerous interface and image manipulation functions are also provided.

out_data Pass back information to After Effects by setting fields within out_data.

An array of the plug-in’s parameters at the time provided in in_data> current_time.

params[0] is the input image (a PF_EffectWorld / PF_LayerDef) to which the effect should be applied.

These values are only valid during certain selectors (this is noted in the selector descriptions).

Parameters are discussed at length here: PF_ParamDef.


The output image, to be rendered by the effect plug-in and passed back to After Effects.

Only valid during certain selectors.


The extra parameter varies with the command sent or (in the case of PF_Cmd_EVENT) the event type.

Used primarily for event management and Parameter Supervision.