Atomic (RW Section)

Atomic
RenderWare Stream Section
Vendor	Criterion Games
Module	Core
Module ID	0x000000
Identifier	0x14
Chunk ID	0x00000014
Versions	All
Hierarchy
Parents: Clump
Children: Struct, Geometry (optional)
Extensions: Right To Render, Particles PLG, Pipeline Set, User Data PLG, Material Effects PLG
File Format

Atomic is a container section used in DFF files as child of a Clump section. It is normally accompanied by a Struct section. An atomic section can associate a Frame with a Geometry.

Atomics are - generally speaking - converted to draw-calls directly. They therefor resemble parts of the geometry (sub-geometries) that should be rendered "as one", utilizing a certain rendering pipeline. They are transformed from object-space directly or indirectly based on the transformation rules that are set for the Frame.

Structure

An atomic section contains Struct, Geometry (optional) and Extension sections. A Struct section has 16 bytes in size (may be different in some RW versions).

struct rwAtomicStruct {
    unsigned int frameIndex;     // Index of the frame within the clump's frame list.
    unsigned int geometryIndex;  // Index of geometry within the clump's geometry list.
    unsigned int flags;          // See below.
    unsigned int unused;         // Typically 0.
};

Flags

There are only 2 options available:

0x01 rpATOMICCOLLISIONTEST - A generic collision flag to indicate that the atomic should be considered in collision tests. 
                             It wasn't used in GTA games since they don't use RW collision system.
0x04 rpATOMICRENDER        - The atomic is rendered if it is in the view frustum. It's set to TRUE for all models by default.

Nested Geometry

An atomic may contain a geometry as a child section. It may exist only if Clump's Geometry List is empty.