Autodesk 3D Studio File Format

# 3D Studio File Format (3ds).

## Autodesk Ltd.

Document Revision 0.1 - May 1996

                     3D-Studio Material-Library File Format (.mli)

                                   Autodesk Ltd.

      Document Revision 0.1

      May 1996   by Robin Fercoq  ( email robin@mail.fc-net.fr )

      Thanks for previous work: the 3d-studio file format (.3ds) doc

      rewritten by Martin van Velsen (email: vvelsen@ronix.ptf.hro.nl )

      based on a work from Jim Pitts (email: jp5.ukc.ac.uk )

      A lot of the chunks are still undocumented if you know what they do

      please email me Robin Feroq, Martin van Velsen or Jim Pitts.

      As I get more information of the file format,I will document it for

      everyone to see. I will post this regurlarly to alt.3d and alt.3d-

      studio and I can be contacted there if my email does not work.

      Disclaimer.

      This document describes the file format of the .mli files generated by

      3d-studio by Autodesk. By using the information contained within you

      free not to hold me liable if, from its use, you f^Hmuck something up.

      OK?

      A warning beforehand. This docs describes the format of mli files produced

      by version 3.0 and higher of 3d-studio. You can find this information at

      byte 29 in the binary file.

      This document describes the matlibs .mli files generated by 3D-Studio 4

      and I think it covers nearly all of its aspects. If not you can

      contact me or Martin van Velsen or Jim Pitts to add or correct.

      First parts of .3DS files include material definitions with the same

      format than .mli, if you want to understand this part of .3DS files

      you can refer to this document.

      Structure

      ---------

      3D-Studio binary files are made up of "chunks".

      A chunk is a block : with an ID which identifies what it stands for,

      a pointer to the next chunk (relative to the beginning of the chunk),

      and a block of data or a set of subchunks (which allows a hierarchy),

      or possibly none of these (void chunk).

      Pointers point to the next chunk of the same level.

      The pointer of the last chunk of a subset points to the next chunk

      level above.

      Chunk ID is 2 bytes, pointer is 4 bytes.

      If I am not clear you can read the .3ds file format doc.

       ( posted on alt.3d and alt.3d-studio )

        It can also be found at:

          "http://www.ptf.hro.nl/odi/free-d/docs/io/3ds/3ds_bin.doc"

       Or

          "http://www.mediatel.lu"

      Remember DOS standard for short and long integers: always

      least significant byte first. I'll write in the natural

      order (most significant first) except for file extracts.

      Main chunk (level 0)  3DAA

      --------------------------

      The Main chunk is the whole .MLI file. Its ID is 3DAA and the pointer

      is in fact the length of the file.

      Begining looks like: AA 3D A0 0F 00 00 ... (for a file of 4k)

      Material chunk (level 1) AFFF

      -----------------------------

      There is only one type of chunk for level 1: the material chunk which

      is the definition for one material.

      This chunk can be found in .3DS files as a subchunk of the EDIT3DS chunk.

      >From now its all the same with .3DS and .MLI .

      Typical material chunk content (level 2 subchunks)

      --------------------------------------------------

       Id    type     function

      A000   asciiz   material name   [the name terminated by a null char]

      A010   S        ambient color   [RGB1 and RGB2]

      A020   S        diffuse color       idem

      A030   S        specular color      idem

      A040   S        shininess       [amount of]

      A041   S        shin. strength     "

      A050   S        transparency       "

      A052   S        trans. falloff     "

      A053   S        reflect blur       "

      A100   intsh    material type   [1=flat 2=gour. 3=phong 4=metal]

      A084   S        self illum      [amount of]

      A240 * V        some trans. falloff amount (not 0)

      A250 * V        some reflect. blur

      A081 * V        two sided

      A083 * V        transparency ADD

      A085 * V        wire on

      A088 * V        face map

      A08A * V        trans. falloff IN

      A08C * V        soften

      A08e * V        3d wire thickness in units (default is in pix)

      A087   float    wire thickness (always present, in case of forced

                                      wire rendering)

      S -> subchunks

      V -> void

      intsh -> short int (2 bytes)

      intlo -> long int  (4 bytes)

      * -> optional.  Absence of such a chunk leads to "none" or

      to a default value.

      Order respected (as 3DS saves the .MLI)

      Non optional chunks are always present.

      Subchunks of these material characteristics (level 3)

      -----------------------------------------------------

      0011   RGB1

      0012   RGB2

      Each of the three color chunks have 2 subchunks that defines their

      colors. It seems that RGB1 is the color with a gamma (which one ?)

      and RGB2 is the same color but as displayed on top of the material

      editor window. But I'm not quite sure why there is two aspects

      of the same color and what it does.

      Anyway, in material color chunks there is always these two subchunks.

      0030   "amount of"

      A252   "displayed amount of bump"

      A short integer that corresponds to the value displayed.

      Oh, the nice maps

      -----------------

      Map and mask chunks (level 2) come after the material characteristics.

      (just after the A087 chunk)

      All these chunks are optional and have subchunks.

      Map chunks IDs:

                     map       mask

      texture1       A200      A33E

      texture2       A33A      A340

      opacity        A210      A342

      bump           A230      A344

      specular       A204      A348

      shininess      A33C      A346

      self illum     A33D      A34A

      reflection     A220      A34C

      In order to respect the order (well, I know, all this is terribly boring)

      (but I wont joke)  (actually, I have no sens of humour)

      (if I had I wouldn't spend my time with computer binary files, would I ?)

      (and especialy not this one...)

      the chunk of the mask of a map follows the chunk of this map.

      It may be of no importance at all thanks to the chunk structure...

      Typical map or mask chunk content (more level 3 subchunks)

      ----------------------------------------------------------

       0030   intsh    amount of

       A300   asciiz   map's file name

       A351   intsh    map options

       A353   float    map filtering blur ( 7% -> 0.07 )

       A354 * float    1/U scale

       A356 * float    1/V scale

       A358 * float    U offset

       A35A * float    V offset

       A35C * float    map rotation angle

      /A360 * RGB      lum or alpha tint first color (default=00 00 00)

      \A362 * RGB      lum or alpha tint secnd color (default=FF FF FF)

      /A364 * RGB      RGB tint R channel color (default=FF 00 00)

       A366 * RGB      RGB tint G channel color (default=00 FF 00)

      \A368 * RGB      RGB tint B channel color (default=00 00 FF)

      Some optional chunks may or may not be present in a given

      map or mask chunk, depending on the options there is

      for the specific map, or for masks.

    --The map options chunk contains two bytes with options coded by bits.

      If read as a short int (ls byte first):

      bit4 bit0: 00 tile (default) 11 decal  01 both

      bit 1: mirror

      bit 2: not used ? (0)

      bit 3: negative

      bit 5: summed area map filtering (instead of pyramidal)

      bit 6: use alpha  (toggles RGBluma/alpha. For masks RGB means RGBluma)

      bit 7: there is a one channel tint (either RGBluma or alpha)

      bit 8: ignore alpha (take RGBluma even if an alpha exists (?))

      bit 9: there is a three channel tint (RGB tint)

      ... not used (0)

      Specific maps

      -------------

      -bump

      For a reason of him 3DS divides the amount of bump by 4.

      ( in the 0030 chunk )

      Nevertheless, the amount actually seen in the material editor

      is coded in a specific subchunk of the bump map chunk: A252

      Just after the A300 chunk.

     -reflection

      The reflection map has no A351 or A353 chunks since there are no

      options for reflection mapping.

      If the map name is only a null caracter, then we have :

     -automatic reflection A310

      A level 2 chunk just after the reflection chunk when there is

      autoreflection. This chunk contains two short ints and two long ints.

      1st short contains 0004. (what does that mean ?)

      2nd short codes for options:

        bit0 seems always set to 1

        bit1 0

        bit2 0

        bit3 First frame only

        bit4 flat mirror

        bitx 0

        next comes a long for the map size

        and the last long is for the "every Nth frame"

    And there it is

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