.FFE File Format

Introduction

An .FFE file holds force feedback effects: the pushes, rumbles and springs that a force feedback joystick or steering wheel can play. The files are made by the Force Editor (FEdit.exe) that came with Microsoft’s DirectX 7 SDK, and a program loads them with IDirectInputDevice7::EnumEffectsInFile, which hands back one DIFILEEFFECT for each effect in the file. The SDK’s Media folder has 110 of them, named for what they feel like: chainsaw.ffe, land2.ffe, lsaber.ffe, helia.ffe.

Each effect is the contents of a DirectInput DIEFFECT structure (how long it lasts, how strong, in which direction, with what envelope) plus the GUID of its type and that type’s parameters: a constant force, a ramp, a sine, square, triangle or sawtooth wave, a spring, damper, inertia or friction, or a custom force. These pages describe the layout of the file and the meaning of every number. The explorer shows every effect and draws its force over time.

Microsoft documented the effects, not the file: the layout here was worked out from the 113 different files of the SDK found on this Mac and checked against the structures of dinput.h.

Structure

The file is a RIFF file of form type FORC. The RIFF size is 0, so a reader has to go on to the end of the file. After the form type there is a 16-byte GUID, then one list of type efct for each effect. A file with no effects is just those 28 bytes. Numbers are little-endian.

Each effect list holds a name, a DIEFFECT whose pointers have been replaced by flags, the effect type’s GUID, a number and then up to four data chunks.

The pages in this reference: the RIFF container, the effect list byte by byte with a worked example, the effect types and their parameters, and how the force curves are drawn.

What the files hold

The 113 different files on this Mac hold 262 effects between them, all from the DirectX 7 SDK. Every one acts on two axes (X and Y, given as offsets in the joystick’s data format), in polar coordinates, at full gain.

75 of the effects have an envelope, 131 have a start delay, 23 are tied to a trigger button and 5 last until stopped.

Telling it apart

A force feedback effect file starts with RIFF, four size bytes and FORC. The explorer takes a file for one only when every effect in it reads right: the list sizes, a DIEFFECT size of 56, the flags in the pointer fields and the sizes of the data chunks. Any other file with the extension .ffe, whatever program made it, opens as bytes.

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