How to Read Maya IFF files in Alias
The Maya IFF file format is not recognized inside file lister as a usable format. You can use the commands file->show->pix or try to use an IFF file as a texture. Maya IFF files can be brought in as images planes for Cameras.
To use IFF files as a texture you must enter the absolute path for the texture and not use the browse button to open file lister.
The structure is based on the use of tags to identify blocks of data called chunks or structures of chunks called groups. Each tag is made up of four characters and is immediately followed by the size of the chunk or group that it describes coded on 4 bytes. Tags are handled as pseudo-character strings and all other data is written in big-endian format.
The main tag types are FORM, CAT, LIST and PROP.
They come in several flavors, such as FOR4, FOR8, CAT4 and CAT8 to specify 4-byte or 8-byte alignment boundaries.
Four tags are used to arrange blocks into groups: FORM, CAT, LIST, and PROP. The first four characters following the size are used to identify the type of the group.
The FORM defines a structure that is like a C struct.
FORM 38 TEXT CHAR 6 "Times" CHAR 12 "Hello World" EOF
is like
struct Text t = {
char *f = "Times";
char *c = "Hello World";
};
The size of the group (38) equals the size of the data it contains (6 plus 12) plus the size of the headers (4 for TEXT, 8 for CHAR 6 and 8 for CHAR 12). In this case, the result is 6+12+4+8+8 = 38.
As in C structures you can nest groups; for example:
FORM 52 TEXT
FORM 8 FONT
CHAR 6 "Times"
LONG 4 <12>
LONG 4 <0>
CHAR 12 "Hello World"
EOF
or in C terms:
struct Text t = {
struct Font f = {
char *n = "Times";
int s = 12;
int d = 0;
};
char *string = "Hello World";
};
This example may not show that blocks are not constrained to use a unique data type and may contain the equivalent of a complete C structure.
The FORM tag separates independent blocks of data that can be handled separately and specifies the meaning of each subunit.
In the example above, the CHAR chunk in the FONT FORM does not mean the same thing as the CHAR chunk in the TEXT FORM. The FORM tag determines how you interpret an ordered set of data types.
The CAT tag defines a concatenation of independent objects with no order relation between them. Two typical uses of CATs are for libraries of objects (pictures in Example 1) or clipboards (Example 2).
CAT 2130 CLIP
FORM 1234 PICT ...
FORM 876 DRAW ...
EOF
Searching through a structured file is generally greatly accelerated, even in a CAT that has no order amongst its members, through the knowledge of the size of every group or chunk specified in the header.
The LIST tag is used to group objects with similar properties, avoiding redundancy. For example, a sequence of equal-sized images might be represented in the following way. One image would have a structure like:
FORM .... PICT
IHDR 32 (image size info)
BODY ... (image data)
EOF
then a sequence of like sized images could be done as follows, sharing the common header information:
LIST ... ANIM
PROP 44 PICT
IHDR 32 (common size info)
FORM ... PICT
BODY .... (data)
FORM ... PICT
BODY .... (data)
FORM ... PICT
BODY .... (data)
EOF
The information in a PROP construct is valid until the end of the LIST. It can be redefined locally in a FORM stastement. (In the above example the common IHDR is valid in all PICTs that don’t include an IHDR block of their own.)
IFF blocks align to 2-byte boundaries. The size specified in the header does not take padding into account. Many computers typically align their memory on 4-byte or 8-byte boundaries. Flib uses eight extra TAGs to let you specify alignment information: