Sort List Crash 2/3

 Introduction

The sort lists in Crash 2/3 are for the most part similar to the ones found in Crash 1. Therefore it is recommended to read the extensive article about Sort Lists in Crash 1 first before reading this article.

 Format

Item 1/Item N: Main Source/Target List 

Offset	Field	Size	Value
0x0	List Size (polygon ID count)	2 bytes	c
0x2	List Type	2 bytes	0
0x4	Polygon IDs	c x 2 bytes	*

Polygon ID

Each Polygon ID has the following format:

WWWSSPPP PPPPPPPP

• W = index of world model
• S = state of the polygon
• P = index of polygon in world model

Since scenery entries in Crash 2/3 have lists for both triangles and quads, the polygon state is used to differentiate between an index for a triangle (SS = 0) and a quad (SS = 1-3).

The polygon state also specifies whether to fully draw the quad or only half of it. A quad can be conceived as a combination of two triangles (ABC and CDA respectively) into a single polygon (ABCD). When only triangle ABC needs to be drawn, SS=1. Should only triangle CDA be drawn, SS=2. Finally, if the entire quad needs to be drawn, SS=3.

 Item 2 to N-1: Difference List

Offset	Field	Size	Value
0x0	List Size minus 2 (in hwords)	2 bytes	c + 2
0x2	List Type	2 bytes	1
0x4	Rel. Index of end of removing nodes minus 2Rel. Index of start of adding nodes minus 2	2 bytes	a + 2
0x6	Rel. Index of end of adding nodes minus 2Rel. Index of start of swapping nodes minus 2	2 bytes	r + 2
Nodes/List
0x8	Removing Nodes	(a - 2) x 2 bytes	*
0x8 + ((a - 2) x 2)	Adding Nodes	(r-a-2) x 2 bytes	*
0x8 + ((r - 2) x 2)	Swapping Nodes	(c-r-a-2) x 2 bytes	*

 Adding/Removing Nodes

Adding and Removing nodes have the same format:

CCCCNNNN NNNNNNNN (WWWSSPPP PPPPPPPP x (C+1))

• C = add/skip count (this node contains C+1 polygon IDs, number of polygon IDs to add/skip)
• N = add/skip index (the polygon IDs from this node will be added to the new list in a progression, or skipped and not added in a retrogression)
• WSP = polygon ID(s) to add when inserting; other than in Crash 1 these polygon IDs in are the same as in the Source/Target lists since the copyflag functionality is abandoned in Crash 2/3.

 Swapping Nodes

Format A: 1BBBBAAA AAAAAAAA [01CCCCCC CCCDDDDD]

Format B: 0000AAAA AAAAAAAA 0000BBBB BBBBBBBB [01CCCCCC CCCDDDDD]

• A = index of Polygon ID A
• B = index of Polygon ID B relative to A + 1
• C = index of Polygon ID C relative to A
• D = index of Polygon ID D relative to C + 17

Besides these swapping node formats familiair from Crash 1, there is another type of 'swapping node' in Crash 2/3 that accounts for the swapping of polygon states. They always come after the formats A - D, at the end of the difference list. The swapping is really a XOR-operation on the SS-value of the polygon ID that it refers to.

Format E: 001XXPPP PPPPPPPP

• X = XOR mask; the new polygon ID WWW**PPP PPPPPPPP = WWW00PPP PPPPPPPP + ((SS^XX) << 11)
• P = Targeted polygon index