Last update 1998/10/05
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Autodesk 3D Studio File Format
3D Studio File Format (3ds).
Document Revision 0.93 - January 1997
3D-Studio File Format (.3ds) Autodesk Ltd. Document Revision 0.93 - January 1997 Rewritten by Martin van Velsen (email: firstname.lastname@example.org ) and Robin Fercoq ( 3ds-bin + mli )(email: email@example.com) Based on documentation by Jim Pitts ( email: firstname.lastname@example.org ) Source update provided by: Albert Szilvasy (email: email@example.com ) A lot of the chunks are still undocumented if you know what they do please email me Martin van Velsen, Robin Feroq or Jimm Pitts. As I get more information on 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. (Also see the 3d-studio material .mli documentation by Robin Feroq.) Disclaimer. This document describes the file format of the 3ds files generated by 3d-studio by Autodesk. By using the information contained within, you agree not to hold any of the authors liable if, from its use, you f^Hmuck something up. OK? Autodesk has at not yet released the offical specifications of the 3d-studio formats. You will therefor receive NO support from Autodesk or any company related to Autodesk concerning the nature and contents of the 3d-studio binary .3ds and .mli formats. A warning beforehand. This docs describes the format of 3ds files produced by version 3.0 and higher of 3d-studio. You can find this version information at byte 29 in the binary file. This document can be found on the regular newsgroups: alt.3d and alt.3d-studio It can also be found at: "http://www.mediatel.lu" ---------------------------------- Contents 1. Introduction 2. Chunks anyone ? 3. 3D Editor chunks 4. Keyframer chunks 5. CODE 1. Introduction ====================== The 3ds file format is made up of chunks. They describe what information is to follow and what it is made up of, it's ID and the location of the next block. If you don't understand a chunk you can quite simply skip it. The next chunk pointer is relative to the start of the current chunk and in bytes. The binary information in the 3ds file is written in a special kind of way. Namely the lest significant byte comes first in an int. For example: 4A 5C (2 bytes in hex) would be 5C high byte and 4A low byte. In a long it is: 4A 5C 3B 8F where 5C4A is the low word and 8F 3B is the high word. And now for the chunks. A chunk is defined as: start end size name 0 1 2 Chunk ID 2 5 4 Pointer to next chunk relative to the place where Chunk ID is, in other words the length of the chunk Chunks have a hierarchy imposed on them that is identified byt it's ID. A 3ds file has the Primary chunk ID 4D4Dh. This is always the first chunk of the file. Within the primary chunk are the main chunks. to give you a preview and a reference to the hierarchy of chunks, below is a diagram to show the diffrent chunk ID's and their place in the file. The chunks are given a name because below the diagram is a list which defines the names to the actual chunk id's. This makes it easier to put it in some source code ( how convenient that some sample code is included ) MAIN3DS (0x4D4D) | +--EDIT3DS (0x3D3D) | | | +--EDIT_MATERIAL (0xAFFF) | | | | | +--MAT_NAME01 (0xA000) (See mli Doc) | | | +--EDIT_CONFIG1 (0x0100) | +--EDIT_CONFIG2 (0x3E3D) | +--EDIT_VIEW_P1 (0x7012) | | | | | +--TOP (0x0001) | | +--BOTTOM (0x0002) | | +--LEFT (0x0003) | | +--RIGHT (0x0004) | | +--FRONT (0x0005) | | +--BACK (0x0006) | | +--USER (0x0007) | | +--CAMERA (0xFFFF) | | +--LIGHT (0x0009) | | +--DISABLED (0x0010) | | +--BOGUS (0x0011) | | | +--EDIT_VIEW_P2 (0x7011) | | | | | +--TOP (0x0001) | | +--BOTTOM (0x0002) | | +--LEFT (0x0003) | | +--RIGHT (0x0004) | | +--FRONT (0x0005) | | +--BACK (0x0006) | | +--USER (0x0007) | | +--CAMERA (0xFFFF) | | +--LIGHT (0x0009) | | +--DISABLED (0x0010) | | +--BOGUS (0x0011) | | | +--EDIT_VIEW_P3 (0x7020) | +--EDIT_VIEW1 (0x7001) | +--EDIT_BACKGR (0x1200) | +--EDIT_AMBIENT (0x2100) | +--EDIT_OBJECT (0x4000) | | | | | +--OBJ_TRIMESH (0x4100) | | | | | | | +--TRI_VERTEXL (0x4110) | | | +--TRI_VERTEXOPTIONS (0x4111) | | | +--TRI_MAPPINGCOORS (0x4140) | | | +--TRI_MAPPINGSTANDARD (0x4170) | | | +--TRI_FACEL1 (0x4120) | | | | | | | | | +--TRI_SMOOTH (0x4150) | | | | +--TRI_MATERIAL (0x4130) | | | | | | | +--TRI_LOCAL (0x4160) | | | +--TRI_VISIBLE (0x4165) | | | | | +--OBJ_LIGHT (0x4600) | | | | | | | +--LIT_OFF (0x4620) | | | +--LIT_SPOT (0x4610) | | | +--LIT_UNKNWN01 (0x465A) | | | | | +--OBJ_CAMERA (0x4700) | | | | | | | +--CAM_UNKNWN01 (0x4710) | | | +--CAM_UNKNWN02 (0x4720) | | | | | +--OBJ_UNKNWN01 (0x4710) | | +--OBJ_UNKNWN02 (0x4720) | | | +--EDIT_UNKNW01 (0x1100) | +--EDIT_UNKNW02 (0x1201) | +--EDIT_UNKNW03 (0x1300) | +--EDIT_UNKNW04 (0x1400) | +--EDIT_UNKNW05 (0x1420) | +--EDIT_UNKNW06 (0x1450) | +--EDIT_UNKNW07 (0x1500) | +--EDIT_UNKNW08 (0x2200) | +--EDIT_UNKNW09 (0x2201) | +--EDIT_UNKNW10 (0x2210) | +--EDIT_UNKNW11 (0x2300) | +--EDIT_UNKNW12 (0x2302) | +--EDIT_UNKNW13 (0x2000) | +--EDIT_UNKNW14 (0xAFFF) | +--KEYF3DS (0xB000) | +--KEYF_UNKNWN01 (0xB00A) +--............. (0x7001) ( viewport, same as editor ) +--KEYF_FRAMES (0xB008) +--KEYF_UNKNWN02 (0xB009) +--KEYF_OBJDES (0xB002) | +--KEYF_OBJHIERARCH (0xB010) +--KEYF_OBJDUMMYNAME (0xB011) +--KEYF_OBJUNKNWN01 (0xB013) +--KEYF_OBJUNKNWN02 (0xB014) +--KEYF_OBJUNKNWN03 (0xB015) +--KEYF_OBJPIVOT (0xB020) +--KEYF_OBJUNKNWN04 (0xB021) +--KEYF_OBJUNKNWN05 (0xB022) A chunk type which you can find all through the file are the color chunks which are called: COL_RGB COL_TRU COL_UNK 2. Chunks anyone ? ========================= Now for the actual numbers, as you will see I used the define, because I ripped that part right out of my code. Be carefull however because there are a lot of new chunk types which were not documented in the original paper by Jim Pitts. //>------ Primary chunk #define MAIN3DS 0x4D4D //>------ Main Chunks #define EDIT3DS 0x3D3D // this is the start of the editor config #define KEYF3DS 0xB000 // this is the start of the keyframer config //>------ sub defines of EDIT3DS #define EDIT_MATERIAL 0xAFFF #define EDIT_CONFIG1 0x0100 #define EDIT_CONFIG2 0x3E3D #define EDIT_VIEW_P1 0x7012 #define EDIT_VIEW_P2 0x7011 #define EDIT_VIEW_P3 0x7020 #define EDIT_VIEW1 0x7001 #define EDIT_BACKGR 0x1200 #define EDIT_AMBIENT 0x2100 #define EDIT_OBJECT 0x4000 #define EDIT_UNKNW01 0x1100 #define EDIT_UNKNW02 0x1201 #define EDIT_UNKNW03 0x1300 #define EDIT_UNKNW04 0x1400 #define EDIT_UNKNW05 0x1420 #define EDIT_UNKNW06 0x1450 #define EDIT_UNKNW07 0x1500 #define EDIT_UNKNW08 0x2200 #define EDIT_UNKNW09 0x2201 #define EDIT_UNKNW10 0x2210 #define EDIT_UNKNW11 0x2300 #define EDIT_UNKNW12 0x2302 #define EDIT_UNKNW13 0x3000 #define EDIT_UNKNW14 0xAFFF //>------ sub defines of EDIT_OBJECT #define OBJ_TRIMESH 0x4100 #define OBJ_LIGHT 0x4600 #define OBJ_CAMERA 0x4700 #define OBJ_UNKNWN01 0x4010 #define OBJ_UNKNWN02 0x4012 //>>---- Could be shadow //>------ sub defines of OBJ_CAMERA #define CAM_UNKNWN01 0x4710 #define CAM_UNKNWN02 0x4720 //>------ sub defines of OBJ_LIGHT #define LIT_OFF 0x4620 #define LIT_SPOT 0x4610 #define LIT_UNKNWN01 0x465A //>------ sub defines of OBJ_TRIMESH #define TRI_VERTEXL 0x4110 #define TRI_FACEL2 0x4111 #define TRI_FACEL1 0x4120 #define TRI_SMOOTH 0x4150 #define TRI_LOCAL 0x4160 #define TRI_VISIBLE 0x4165 //>>------ sub defs of KEYF3DS #define KEYF_UNKNWN01 0xB009 #define KEYF_UNKNWN02 0xB00A #define KEYF_FRAMES 0xB008 #define KEYF_OBJDES 0xB002 //>>------ these define the different color chunk types #define COL_RGB 0x0010 #define COL_TRU 0x0011 #define COL_UNK 0x0013 //>>------ defines for viewport chunks #define TOP 0x0001 #define BOTTOM 0x0002 #define LEFT 0x0003 #define RIGHT 0x0004 #define FRONT 0x0005 #define BACK 0x0006 #define USER 0x0007 #define CAMERA 0x0008 // 0xFFFF is the actual code read from file #define LIGHT 0x0009 #define DISABLED 0x0010 #define BOGUS 0x0011 3. 3D Editor Chunks =========================== So far for the quick stuff now the more detailed info. * Main chunks The main chunk ( the primary chunk of 0x4D4D that is ) is actually the complete file. So the size of this chunk is the size of the file minus the main chunk header. There are two more main chunks, the 3d-editor chunk and the keyframer chunk: id 3D3D Start of Editor data ( this is also the place where the objects are ) B000 Start of Keyframer data Directly after a Main chunk is another chunk. This could be any other type of chunk allowable within its main chunks scope. ( see diagram ) * Subchunks of 3D3D id Description 0100 Part of configuration 1100 unknown 1200 Background Color 1201 unknown 1300 unknown 1400 unknown 1420 unknown 1450 unknown 1500 unknown 2100 Ambient Color Block 2200 fog ? 2201 fog ? 2210 fog ? 2300 unknown 3000 unknown 3D3E Editor configuration main block 4000 Definition of an Object AFFF Start of material list * Subchunks of AFFF - Start of material list * A000 - material name - This chunk contains the name of the material which is an ASCIIZ string ( More material chunks are explained in the doc about 3d-studio .mli files. The chunk types mentioned in that doc are exactly the same as in the .3ds file ) * Subchunks of 3D3E - Editor configuration id Description 7001 Start of viewport indicator 7011 Viewport definition ( type 2 ) 7012 Viewport definition ( type 1 ) 7020 Viewport definition ( type 3 ) The 3D3E chunk is a curious one because it contains a lot of redundant data. ( or so it seems ) The most important chunk is 7020. this chunk describes the 4 viewports wich are active in the editor. I assume that U are using the 4 normal viewport layout, because I have not tested it with other configurations. The editor confid will contain 5x chunk 7020 and 5x chunk 7011. only the first 4 7020 chunks are important for how the viewports look like. I guess that the other chunks only give additional info, but I am not sure. The things you are looking for in these chunks is at byte: 6 & 7 ( as offset from the first 6 bytes chunk header and pointer ) these bytes ( unsigned int ) contain the info at to what view is used, with the following id's: id Description 0001 Top 0002 Bottom 0003 Left 0004 Right 0005 Front 0006 Back 0007 User FFFF Camera 0009 Light 0010 Disabled * Subchunks of 4000 - Object description Block - first item of Subchunk 4000 is an ASCIIZ string of the objects name. ASCIIZ means a string of charakters ended by a zero. Remember an Object can be a Camera a Light or a mesh id Description 4010 unknown 4012 shadow ? 4100 Triangular Polygon List ( Contains only subchunks ) 4600 Light 4700 Camera ( Mapping: These chunks are optional. They stand just after the vertex list when the object is mapped. ) * Subchunks of 4100 - Triangular Polygon List id Description 4110 Vertex List 4111 Vertex Options 4120 Face List 4130 Face Material 4140 Mapping Coordinates 4150 Face smoothing group 4160 Translation Matrix 4165 Object visible/invisble 4170 Standard Mapping * 4110 - Vertex List start end size type name 0 1 2 unsigned int Total vertices in object 2 5 4 float X-value 6 9 4 float Y-value 10 13 4 float Z-value bytes 2..13 are repeated times the total amount of vertices in the object * 4111 - Vertex Options First 2 bytes: number of vertices. Then a short int for each vertex: bit 0-7 0 bit 8-10 x bit 11-12 0 bit 13 vertex selected in selection 3 bit 14 vertex selected in selection 2 bit 15 vertex selected in selection 1 bit 8-10 are just like random. From a save to another of the same scene it may change. Other bits (0-7 and 11-12) have effects on visibility of vertex. The 4111 chunk can be deleted without much influence, 3ds will still load the file all right. * 4120 - Face list start end size type name 0 1 2 unsigned int total polygons in object (numpoly) 2 3 2 unsigned int number of vertex A 4 5 2 unsigned int number of vertex B 6 7 2 unsigned int number of vertex C 8 9 2 unsigned int face info (*) repeats 'numpoly' times for each polygon. The first three ints are the three vertices of the face. 0 stands for the first vertex defined in the vertex list. The order has a purpose: to give the direction for the normal of each face. If you turn a screw (standard screw) in the way the vertices indicate you will find the normal. If vertices given in order are A B C: C ^ | A----->B This means unscrewing => the normal points out of the screen. (*) this number is is a binary number which expands to 3 values. for example 0x0006 would expand to 110 binary. The value should be read as 1 1 0 .This value can be found in 3d-studio ascii files as AB:1 BC:1 AC:0 .Which probably indicated the order of the vertices. For example AB:1 would be a normal line from A to B. But AB:0 would mean a line from B to A. bit 0 AC visibility bit 1 BC visibility bit 2 AB visibility bit 3 Mapping (if there is mapping for this face) bit 4-8 0 (not used ?) bit 9-10 x (chaotic ???) bit 11-12 0 (not used ?) bit 13 face selected in selection 3 bit 14 face selected in selection 2 bit 15 face selected in selection 1 * 4130 - Face Material Chunk If the object is all default material there is no 4130 chunk. In fact, there is one 4130 chunk for each material present on the object. Each 4130 face material chunks begins with an asciiz of a material, then after the null character is a short int that gives the number of faces of the object concerned by this material, then there is the list itself of these faces. 0000 means the first face of the (4120) face list. ************ Read the Doc on MLI files for more info on ************** ************ Mapping and Materials ************** * 4140 Mapping coordinates. First 2 bytes: number of vertices. Then, for each vertex 2 floats that give the mapping coordinates. That is, if a point is at the center of the map it will have 0.5 0.5 as mapping coordinates. * 4150 - Face Smoothing Group nfaces*4bytes If read as long int, the nth bit indicate if the face belongs or not to the nth smoothing group. * 4160 Local axis Local axis info. The three first blocks of three floats are the definition (in the absolute axis) of the local axis X Y Z of the object. And the last block of three floats is the local center of the object. * 4170 Standard mapping First 2 bytes: type of mapping 0 => plannar or specific (in this case, like mapping from the lofter, the information of this chunk is irrelevant) 1 => cylindrical 2 => spherical then come 21 floats that describe the mapping. * 4600 - Light start end size type name 0 3 4 float Light pos X 4 7 4 float Light pos Y 8 11 4 float Light pos Z after this structure check for more chunks. id Description ( full description later ) 0010 RGB color 0011 24 bit color 4610 Light is a Spot light 4620 Light is off/on ( Boolean ) * 4610 - Spot Light start end size type name 0 3 4 float Target pos X 4 7 4 float Target pos X 8 11 4 float Target pos X 12 15 4 float Hotspot 16 19 4 float Falloff * 0010 - RGB Color start end size type name 0 3 4 float Red 4 7 4 float Green 8 11 4 float Blue * 0011 - RGB Color - 24 bit start end size type name 0 1 1 byte Red 1 1 1 byte Green 2 2 1 byte Blue * 4700 - Camera Describes the details of the camera in the scene start end size type name 0 3 4 float Camera pos X 4 7 4 float Camera pos Y 8 11 4 float Camera pos Z 12 15 4 float Camera target X 16 19 4 float Camera target X 20 23 4 float Camera target X 24 27 4 float Camera bank ( rotation angle ) 28 31 4 float Camera lens 4. Keyframer Chunks ========================== * Keyframer chunk id Description B00A unknown 7001 See first description of this chunk B008 Frames B009 unknown B002 Start object description * B008 - Frame information simple structure describing frame info start end size type name 0 3 4 unsigned long start frame 4 7 4 unsigned long end frame *B002 - Start of Object info Subhunks id Description B010 Name & Hierarchy B011* Name Dummy Object B013 unknown B014* unknown B015 unknown B020 Objects pivot point ? B021 unknown B022 unknown * B010 - Name & Hierarchy descriptor start end size type name 0 ? ? ASCIIZ Object name ? ? 2 unsigned int unknown ? ? 2 unsigned int unknown ? ? 2 unsigned int Hierarchy of Object The object hierarchy is a bit complex but works like this. Each Object in the scene is given a number to identify its order in the tree. Also each object is orddered in the 3ds file as it would appear in the tree. The root object is given the number -1 ( FFFF ). As the file is read a counter of the object number is kept. Is the counter increments the objects are children of the previous objects. But when the pattern is broken by a number what will be less than the current counter the hierarchy returns to that level. for example. object hierarchy name A -1 B 0 This example is taken C 1 from 50pman.3ds D 2 E 1 I would really reccomend F 4 having a look at one of the G 5 examples with the hierarchy H 1 numbers to help work it out. I 7 J 8 K 0 L 10 M 11 N 0 O 13 P 14 A +-----------------+----------------+ B K N +----+----+ | | C E H L O | | | | | D F I M P | | G J Still not done with this chunk yet ! If the object name is $$$DUMMY then it is a dummy object and therefore you should expect a few extra chunks. * B011 - Dummy objects name. Names a dummy object. ASCIIZ string. * B020 - Pivot Point ? The Objects pivot point. Not quite sure what the first five floats do yet ( ideas ?). start end size type name 0 3 4 float unknown 4 7 4 float unknown 8 11 4 float unknown 12 16 4 float unknown 16 19 4 float unknown 20 23 4 float unknown 24 27 4 float Pivot Y 28 32 4 float Pivot X 5. CODE ============================= !!!!!!!!!!! The source code is not UP-TO-DATE it is written after rev 0.9 of this Doc It will be updated when I can find the time ( or maybe YOU can) If the code looks like it has been written by a a twelve year old, then looks do decieve, I like very simple and easy to read source code. All that matters is that it does the trick. 3dsbin-read.c by Martin van Velsen.
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