.LWO File Format – Surface blocks

BLOK

BLOK { header[SUB-CHUNK], attributes[SUB-CHUNK] * }

The first sub-chunk is the header, whose ID gives the block type. The sub-chunks after it depend on the type; texture layers usually include a TMAP.

Block header

block-header { ordinal[S0], block-attributes[SUB-CHUNK] * }

Ordinal strings

When several blocks apply to one channel, or several shaders to the surface, the ordinal string sets their order: a reader sorts the blocks by comparing ordinals as C strings. An ordinal is a fraction written in base 255, using the byte values 1 to 255 as digits (0 ends the string), so a new block can always be placed between two others, much as 0.55 fits between 0.5 and 0.6. An ordinal must not end in the digit 1, just as a decimal fraction gains nothing from a trailing 0: \x80 and \x80\x01 would leave no room between them.

TMAP – Texture mapping

TMAP { attributes[SUB-CHUNK] * }, used by image maps and procedurals to map object or world coordinates into texture space:

IMAP – Image maps

PROC – Procedural textures

GRAD – Gradients

A gradient maps an input value through a line of colour keys.

SHDR – Shaders

Shaders run after all channels and texture layers, in ordinal order. Their header uses only ENAB, and one sub-chunk describes them: