RRM Format (Mythos Software)

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The RRM Format (Mythos Software) is a container for room-specific data in The Lost Files of Sherlock Holmes: The Case of the Serrated Scalpel.

File format


The header has this format:

Data type Name Description
char[32] magicText "\r\n\nHOLMES RESOURCE FILE V2.1\r\n\n\x1A"
BYTE[7] magicBytes The same in all files: 00 14 9C 0E 74 50 05. Unknown meaning.
BYTE isPacked 09 = unpacked, 0A = packed.
UINT32LE dirOffset Offset of the directory, described below.


The header is followed by zero or more animation offsets and data:

Data type Name Description
UINT32LE[nAnims] animOffsets Offsets to VGS data for animations.
VGSChunk[nAnims] anims Animations in the Visage format.

nAnims is found in the directory that follows. RRM files are not parsed sequentially.


The directory gives total numbers or sizes of various resources.

Data Type Name Description
UINT16LE nObjects Number of logical room objects, defined below.
UINT16LE nSprites Number of VGS chunks associated with room objects.
UINT16LE nAnims Number of VGS chunks in the previous section.
UINT16LE textSize Size of the text block below, containing object descriptions.
UINT16LE sequencesSize Size of the sequence block below, defining sprite frame orders.
UINT16LE unknown Always zero.

Sprites are persistent graphics for room objects, typically lasting the duration of play in the room. Animations are typically used for one-off events.

Sprite Definitions

Next comes a table defining the sprites:

Data Type Name Description
SPRITEDEF[nObjects] spriteDefs See below for SPRITEDEF definition.

Note that there are nObjects SPRITEDEFs not nSprites. There are always at least as many objects as there are sprites, and the table is null-padded.

DataType Name Description
UINT32LE spriteSize Size of the VGS chunk for this sprite.
UINT8 numFrames Number of frames in the sprite.
char[9] spriteName Internal name of the sprite.

Object Data

Objects are the game's most complex data structure and will be defined later on this page. For now, they will be viewed simply as 569-byte chunks. They and their remaining associated data follow:

DataType Name Description
OBJECTDEF[nObjects] objects Logical room objects.
char[textSize] objectText ASCIIZ descriptions used when looking at an object.
BYTE[sequencesSize] sequenceBlock Object sequences, defined later on this page.
VGSChunk[nSprites] sprites VGS chunks for sprites defined in the SPRITEDEFs.

The VGS chunks for sprites can be read sequentially using the size field in the SPRITEDEFs.

Animation Structures

Next come structures defining the behaviour of animations:

DataType Name Description
ANIMDEF[nAnims] animDefs See below.
DataType Name Description
char[12] name Name of the animation structure.
BYTE[30] sequence Sequence defining frame order, etc. Sequences are defined later.
UINT16LE x Topleft coordinate for first animation frame.
UINT32LE size Size of VGS chunk in the block near the top of the file.
UINT16LE state Related to state field of objects, explained later.
UINT8 drawOptions Related to drawOptions field of objects, explained later.
HPOS startPos Holmes' standing position when the animation begins.
HPOS endPos Holmes' standing position when the animation ends.

HPOS is a type also used elsewhere in this file. It defines a 'stance' for Holmes:

DataType Name Description
UINT16LE x Screen coordinate * 100
UINT16LE loopNum Index into Holmes' list of lists of frames, to be added here later. Essentially, the direction he is facing and whether he is walking or standing still.

The game does coordinate calculations internally in multiples of 100, for example the centre of the screen would be 16000x10000. This was presumably done to avoid floating point in diagonal move deltas.

Pathing Data

Next comes a number of data structures defining how Holmes moves around the room.

DataType Name Description
UINT16LE boxBlockSize Size of the following block of BOXDEFs. Let nBoxes = boxBlockSize / 10.
BOXDEF[nBoxes] boxDefs Boxes as defined below.

BOXDEF is defined as follows:

DataType Name Description
UINT16LE x Coordinates defining a walkable area on the screen.
UINT16LE flags Unknown purpose.

A magic byte 0xFE follows, and then a lookup table and waypoints data chunk:

DataType Name Description
INT16LE[nBoxes][nBoxes] lookup See below for explanation.
UINT16LE waypointsSize Size of following waypoints data chunk.
BYTE[waypointsSize] waypoints Waypoints data chunk.

This data is used when Holmes tries to walk from one box to another. The boxes may not be connected and require travel through other boxes. Let src be the index of the box he is in, and dest be the index of the destination box. lookup[src][dest] where src is a column in the table will yield an index into the waypoints chunk. A waypoints entry looks like this:

DataType Name Description
UINT8 nWaypoints Number of waypoints that follow.
WAYPOINT[nWaypoints] waypoints List of screen coordinates that Holmes should walk towards on his path from src to dest. Each coordinate is UINT16LE x, UINT8 y.

Note that all entries on the main diagonal of the lookup matrix are 0, and at offset 0 in the waypoints block is a set of 0 waypoints, because there is no path needed from a box to itself. Additionally, all entries below the main diagonal are -1, indicating a redundant entry. This is because paths are reversible and the upper half contains all data needed.

Next come the exit boxes:

DataType Name Description
UINT8 nExitDefs Number of following EXITDEFs.
EXITDEF[nExitDefs] exitDefs Exits as defined below.

EXITDEF is defined as follows:

DataType Name Description
UINT16LE x Coordinates defining a walkable area on the screen.
UINT16LE roomNum Destination room number.
UINT16LE unknown Always 1.
UINT16LE destX Holmes' position on entering the new room.
UINT16LE destY
UINT16LE destLoop Holmes' animation loop on entering the new room.

Walking on an EXITDEF area causes Holmes to leave the room.

Concluding the pathing data, Holmes' starting position in the room:

DataType Name Description
HPOS startPos Holmes' starting position on entering the current room.


A list of sound effects follows.

DataType Name Description
UINT8 nSoundDefs Number of sound effect names that follow.
char[nSoundDefs][9] soundDefs 8-byte sound effect name, padded with nulls, followed by byte 09. The sound effect is found in the LIB archive SND.SND

Room object sequences, defined later on this page, can cause a sound effect to be played by index into this list.

Palette and Background

The remainder of the .RRM consists of a 768-byte VGA Palette and a 320x138 background image.

The palette is required to construct the animations and sprites earlier in the file. The programmer may choose between parsing through the file and constructing the animations and sprites later, or seeking to the end of the file immediately, since the palette is always at the fixed offset of EOF - (320 * 138 + 768).

Object Structure

Objects are logical entities in a room that affect gameplay. They may have an associated sprite, or they may have not and function as an invisible trigger area. Still other objects may have no spatial meaning and represent state transitions.

Objects always occupy 569 bytes. Many fields only have meaning at runtime.

FARPTR in the DataType column refers to a 32-bit memory location composed of UINT16LE offset, UINT16LE segment. These runtime fields are included for completeness.

Offset DataType Name Description
0 char[12] name Internal ASCIIZ object name.
12 char[41] hoverText ASCIIZ text shown on the status line when the player hovers over the object.
53 FARPTR textPtr runtime: pointer to ASCIIZ text description.
57 FARPTR seqPtr Initially, the first UINT16LE in this field holds the offset of this object's sequence data in the room sequenceBlock.
runtime: afterwards, the field is used as a FARPTR to the sequence.
61 FARPTR spritePtr runtime: pointer to VGS sprite for the object.
65 FARPTR framePtr runtime: pointer to current sprite frame.
69 BYTE unknown always 0
70 BYTE unknown always 0
71 UINT16LE seqIndex runtime: current position in the object's sequence.
73 UINT16LE unknown always 0
75 UINT16LE x Topleft screen coordinate of the object.
77 UINT16LE y
79 INT16LE deltaX runtime: position delta for moving object.
81 INT16LE deltaY
83 UINT16LE state These values occur in the .RRM:
4: active, with sprite
6: active, without sprite
7: inactive
85 UINT16LE frameX runtime: dimensions of the current sprite frame.
87 UINT16LE frameY
89 UINT16LE frameWidth
91 UINT16LE frameHeight
93 BYTE[4] unknown always 0
97 UINT8 intBehave encodes various things that happen when the user interacts with the object.
98 UINT8 defBehave default interaction, as an index into the menu commands (1=Look, 2=Talk, 3=Move, etc.)
99 INT16LE[3] flags story progress flags, to be described elsewhere.
105 UINT16LE hoverX Area occupied by an object with no sprite. 0,0 for objects with sprites.
107 UINT16LE hoverY
109 UINT16LE unknown always 0
111 UINT8 spriteNum If 0, the object has no sprite. If > 0, subtract 1 and use as index into room sprite list.
112 UINT16LE spriteFrames Number of frames in the object's sprite.
114 BYTE drawOptions Bitfield controlling drawing of the object's sprite. The following bits are known so far:
0 and 2: OR these bits together and interpret as a number from 0..3 representing drawing layer, with 0 as backmost and 3 as frontmost.
1: if 1, the sprite is mirrored.
115 ACTIONDEF openAction Behaviour when opening the object. See below for ACTIONDEF.
165 BYTE onCollision Unknown value encoding what to do when Holmes collides with the object.
166 BYTE unknown unknown purpose
167 BYTE seqRepCounter runtime: counts how many times the object's sequence's current loop has repeated.
168 UINT16LE approachX Holmes walks to this position when approaching an object to interact with it.
170 UINT8 approachY
171 UINT8 approachLoop
172 BYTE unknown unknown purpose
173 ACTIONDEF closeAction Behaviour when closing the object. See below for ACTIONDEF.
223 UINT8 seqPrevIndex runtime: previous sequence loop position, saved by sequence call command.
224 UINT8 seqFinalFrame runtime: final frame of sequence shorthand iterator, to be defined later in sequence section.
225 UINT16LE textOffset Offset of object's ASCIIZ description text in room textBlock, used when Holmes uses Look interaction on the object.
227 UINT8 seqLoopCounter runtime: number of times a called sequence loop has repeated.
228 UINT16LE seqSize Size of object's sequence data in the room sequenceBlock.
230 BYTE unknown always 0
231 ACTIONDEF moveAction Behaviour when moving the object. See below for ACTIONDEF.
281 BYTE[8] unknown always 0
289 ACTIONDEF2[4] extraActions See below for ACTIONDEF2.

ACTIONDEF handles open, close, move actions. It is defined as follows:

DataType Name Description
BYTE animNum Animation number to play when interacting. 99 means a TLK script is to be loaded.
BYTE unknown unknown purpose
char[4][12] names Names of other room objects to toggle or TLK scripts to load.

ACTIONDEF2 handles other actions like pickup. It is defined as follows:

DataType Name Description
BYTE animNum Animation number to play when interacting. 99 means a TLK script is to be loaded.
BYTE unknown unknown purpose
char[4][12] names Names of other room objects to toggle or TLK scripts to load.
INT16LE flag story progress flag, either a prerequisite for or result of the action.
BYTE[6] unknown always 0
char[12] lastName Always contains either a TLK script name, or special tags like *SELF*, *PICKUP*.

Sequence Structure

Coming soon.


This file format was reverse engineered by Ceidwad. If you find this information helpful in a project you're working on, please give credit where credit is due. (A link back to this wiki would be nice too!)