Havok collision (zone_physics)

Insomniac engineCollision and physicsApplies toSunset

Collision is a Havok binary packfile in each .zone_physics asset, section 9629C287 of its DAT1. Of the 1,112 zone_physics assets, all LZ4-compressed, 898 have exactly that one section; 214 have no section and are empty 83-byte DAT1 placeholders. Observed The numbers are from a recorded census of the PC build 3373500; the install is no longer available. Observed

Packfile

All 898 packfiles share one header variant: Havok 2013.2.0-r1, file version 11, layout bytes 08 01 00 01 (8-byte pointers, little endian, no padding reuse, empty base class optimisation), and three sections __classnames__, __types__ and __data__, with the contents in section 2 at offset 0 and flags 0. Observed __types__ is empty, so no reflection data ships and class layouts must come from elsewhere. Observed

Packfile section header (version 11)64 bytesSunset100% known

Fixup tables are padded with 0xFF to 16 bytes, so a table of 12-byte entries need not be a multiple of 12.

ProvenObservedSourcedInferredUnknownNot described

Offset	Size	Type	Field	Confidence	Notes
0x0	19	char[19]	tag	Observed	__classnames__, __types__ or __data__
0x13	1	u8 = 0xFF	marker	Observed
0x14	4	u32	absolute data start	Observed
0x18	4	u32	local fixups	Observed	offset relative to the data start
0x1C	4	u32	global fixups	Observed
0x20	4	u32	virtual fixups	Observed
0x24	4	u32	exports	Observed
0x28	4	u32	imports	Observed
0x2C	4	u32	end	Observed
0x30	16	u8[16] = 0xFF	padding	Observed

Class-name entries are u32 signature, byte 0x09, NUL-terminated name. A parser walks every table of all 898 files without error and every virtual fixup resolves to a class-name entry. Observed

Shape census

Each virtual fixup is one object instance. Over the 898 files: Observed

Class	Instances	Files
`hkRefCountedProperties`	109,106	898
`hknpShapeMassProperties`	109,106	898
`hknpCompressedMeshShape`	107,622	896
`hknpStaticCompoundShape`	1,757	898
`hknpConvexPolytopeShape`	1,484	286
`hkRootLevelContainer`	898	898
`hknpPhysicsSceneData`	898	898
`hknpPhysicsSystemData`	898	898
`hknpCapsuleShape`	39	10
`hknpSphereShape`	5	5

This is Havok’s “new physics” (hknp, 2013+), not hkp: there is no hkpRigidBody, hkpBvCompressedMeshShape, hkpMoppBvTreeShape or hkpExtendedMeshShape at all. Observed 109,106 equals 107,622 + 1,484 exactly, so the compressed-mesh and convex-polytope shapes are the ones with mass properties (the attachment itself is inferred). Observed The compressed mesh is about 98% of shape instances. Observed In hex_212 the six files (main 713,663 B / 1.95 MB packfile, _ground, _low, _gameplay, two elevated-train prefabs) hold 725 compressed meshes, 13 convex polytopes and 10 static compounds. Observed

Structure

Each file probably nests as: hkRootLevelContainer → hknpPhysicsSceneData → hknpPhysicsSystemData (bodies with transforms and shape references) → hknpStaticCompoundShape (instances: a transform and a child shape) → many hknpCompressedMeshShape, so a shape’s world transform would come from its body and its compound instance. Inferred The compressed mesh data is probably an hkcdStaticMeshTree with sections, codec parameters (offset and scale), quantised packed vertices (u32, 11/11/10 bits), shared vertices (u64, 21/21/22 bits over the tree box) and primitives (four u8 indices, quad or triangle) with per-primitive material data, as the same class is decoded in the Havok versions of the FromSoftware games; Havok 2013 field offsets may differ from those. Inferred Every hkArray data pointer is a local fixup, which lets array starts and counts be found by inspection. Inferred Per-triangle surface ids may map to Insomniac’s own surface types; none has been seen. Unknown

How is an hknpCompressedMeshShape laid out in Havok 2013.2.0-r1?

The packfile layer reads completely, but the shape data inside hknpCompressedMeshShape is not decoded; with __types__ empty its field offsets have to be found by inspection.

Do the shapes carry per-triangle surface ids?

Whether the compressed mesh holds material ids that map to skatable surfaces is unknown.