3DS materials: colours, shading, texture maps and tiling

Each material is an AFFF chunk (lib3ds MAT_ENTRY) in the 3D editor chunk. It has no data of its own; its sub-chunks set the name, colours, shading and texture maps. Meshes name the materials they use in their material group chunks. The same chunks make up a material library (.mli) file.

Name, colours and percentages

ID	Name	Data	Meaning
`A000`	`MAT_NAME`	strz	Material name
`A010`	`MAT_AMBIENT`	Colour sub-chunks	Ambient colour, usually written as `0011` and `0012`
`A020`	`MAT_DIFFUSE`	Colour sub-chunks	Diffuse colour
`A030`	`MAT_SPECULAR`	Colour sub-chunks	Specular colour
`A040`	`MAT_SHININESS`	Percentage sub-chunk	Shininess
`A041`	`MAT_SHIN2PCT`	Percentage sub-chunk	Shininess strength
`A050`	`MAT_TRANSPARENCY`	Percentage sub-chunk	Transparency
`A052`	`MAT_XPFALL`	Percentage sub-chunk	Transparency falloff
`A053`	`MAT_REFBLUR`	Percentage sub-chunk	Reflection blur
`A084`	`MAT_SELF_ILPCT`	Percentage sub-chunk	Self-illumination
`A087`	`MAT_WIRE_SIZE`	float	Wire thickness

Percentages are usually written with the integer percentage chunk 0030.

Material flags

Flag chunks with no data: present means on.

ID	Name	Meaning
`A080`	`MAT_SELF_ILLUM`	Self-illumination on
`A081`	`MAT_TWO_SIDE`	Two-sided: both faces of each triangle are drawn
`A082`	`MAT_DECAL`	Decal
`A083`	`MAT_ADDITIVE`	Additive transparency
`A085`	`MAT_WIRE`	Render as wireframe
`A088`	`MAT_FACEMAP`	Face mapping: each face takes the whole texture
`A08A`	Not named	“In tranc” in 3dsinfo.txt; meaning unknown
`A08C`	`MAT_PHONGSOFT`	Soften (Phong shading softened)
`A08E`	`MAT_WIREABS`	Wire thickness is in units, not pixels
`A240`	`MAT_USE_XPFALL`	Use the transparency falloff
`A250`	`MAT_USE_REFBLUR`	Use the reflection blur
`A252`	Not named	“Bump map present (true percent)” in 3dsinfo.txt; data unknown

A100 – Shading

Value	Shading
0	Wireframe
1	Flat
2	Gouraud
3	Phong
4	Metal

The data is one word. 3dsinfo.txt calls the chunk “render type”.

Texture maps and masks

A material can have up to eight maps, each with an optional mask. Every map and mask chunk holds the same map sub-chunks.

Map	ID	Name	Mask ID	Mask name
Texture 1	`A200`	`MAT_TEXMAP`	`A33E`	`MAT_TEXMASK`
Texture 2	`A33A`	`MAT_TEX2MAP`	`A340`	`MAT_TEX2MASK`
Opacity	`A210`	`MAT_OPACMAP`	`A342`	`MAT_OPACMASK`
Bump	`A230`	`MAT_BUMPMAP`	`A344`	`MAT_BUMPMASK`
Specular	`A204`	`MAT_SPECMAP`	`A348`	`MAT_SPECMASK`
Shininess	`A33C`	`MAT_SHINMAP`	`A346`	`MAT_SHINMASK`
Self-illumination	`A33D`	`MAT_SELFIMAP`	`A34A`	`MAT_SELFIMASK`
Reflection	`A220`	`MAT_REFLMAP`	`A34C`	`MAT_REFLMASK`

Map sub-chunks

ID	Name	Data	Meaning
`0030`	`INT_PERCENTAGE`	word	Strength of the map, 0 to 100
`A300`	`MAT_MAPNAME`	strz	Image file name, in MS-DOS 8.3 form in files from the DOS program
`A351`	`MAT_MAP_TILING`	word	Map options; see below
`A353`	`MAT_MAP_TEXBLUR`	float	Blur
`A354`	`MAT_MAP_USCALE`	float	u scale (lib3ds and Assimp; 3dsinfo.txt says v)
`A356`	`MAT_MAP_VSCALE`	float	v scale (lib3ds and Assimp; 3dsinfo.txt says u)
`A358`	`MAT_MAP_UOFFSET`	float	u offset
`A35A`	`MAT_MAP_VOFFSET`	float	v offset
`A35C`	`MAT_MAP_ANG`	float	Rotation angle
`A360`	`MAT_MAP_COL1`	3 bytes	First tint colour for luma or alpha tinting
`A362`	`MAT_MAP_COL2`	3 bytes	Second tint colour
`A364`	`MAT_MAP_RCOL`	3 bytes	Colour that replaces the image’s red channel in RGB tinting
`A366`	`MAT_MAP_GCOL`	3 bytes	Colour that replaces the green channel
`A368`	`MAT_MAP_BCOL`	3 bytes	Colour that replaces the blue channel

The order of the two scale chunks is a known disagreement between the sources; lib3ds and Assimp agree with each other. Tint colours are red, green, blue bytes.

A351 – Map options

Bit	Value	lib3ds name	Meaning
0	`0x0001`	`DECALE`	Decal
1	`0x0002`	`MIRROR`	Mirror the image on each repeat
2	`0x0004`	None	Unknown
3	`0x0008`	`NEGATE`	Invert the image
4	`0x0010`	`NO_TILE`	No tiling
5	`0x0020`	`SUMMED_AREA`	Summed-area filtering instead of pyramidal
6	`0x0040`	`ALPHA_SOURCE`	Use the image’s alpha channel as the map value
7	`0x0080`	`TINT`	Luma tint with `A360` and `A362`
8	`0x0100`	`IGNORE_ALPHA`	Ignore the image’s alpha channel
9	`0x0200`	`RGB_TINT`	RGB tint with `A364` to `A368`

The names are lib3ds’s; the meanings follow from them and from 3D Studio’s map options. Bits 10 to 15 are not known to be used.

A310 – Automatic reflection map

In place of a reflection image, 3D Studio can render a cubic reflection map of the scene. The A310 chunk (lib3ds MAT_ACUBIC) sets it up:

Offset	Type	Meaning
0	byte	Unknown
1	byte	Anti-aliasing: 0 none, 1 low, 2 medium, 3 high
2	word	Flags: `0x0001` use the automatic map, `0x0004` render the first frame only, `0x0008` flat mirror
4	dword	Map size
8	dword	Render every `n`th frame

Procedural texture data

Chunks A320 to A338 hold settings for SXP procedural textures, plug-ins for 3D Studio, one chunk per map or mask:

ID	Name	For
`A320`	`MAT_SXP_TEXT_DATA`	Texture 1
`A321`	`MAT_SXP_TEXT2_DATA`	Texture 2
`A322`	`MAT_SXP_OPAC_DATA`	Opacity
`A324`	`MAT_SXP_BUMP_DATA`	Bump
`A325`	`MAT_SXP_SPEC_DATA`	Specular
`A326`	`MAT_SXP_SHIN_DATA`	Shininess
`A328`	`MAT_SXP_SELFI_DATA`	Self-illumination
`A32A`	`MAT_SXP_TEXTMASK_DATA`	Texture 1 mask
`A32C`	`MAT_SXP_TEXT2MASK_DATA`	Texture 2 mask
`A32E`	`MAT_SXP_OPACMASK_DATA`	Opacity mask
`A330`	`MAT_SXP_BUMPMASK_DATA`	Bump mask
`A332`	`MAT_SXP_SPECMASK_DATA`	Specular mask
`A334`	`MAT_SXP_SHINMASK_DATA`	Shininess mask
`A336`	`MAT_SXP_SELFIMASK_DATA`	Self-illumination mask
`A338`	`MAT_SXP_REFLMASK_DATA`	Reflection mask

Their content belongs to each plug-in and is not documented.

.3DS File Format – Materials and maps