Difference between revisions of "FF7/Field/Walkmesh"

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=== Section 5: Walkmesh ([[User:Kero|Kero]]) ===
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=== Section 5: Walkmesh ([[User:Kero|Kero]]) ===
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<div class="thumb tright"><div class="thumbinner" style="width: 182px">[[File:Field_Wutai.jpg|180px|[[Image:180px-Field_Wutai.jpg]]]]<div class="thumbcaption"><div class="magnify">[[File:Field Wutai.jpg]]</div>Wutai Walkmesh</div></div></div>
  
 
Every every offset is here relative, 00 is at the start of section 5 (after length indicator).
 
Every every offset is here relative, 00 is at the start of section 5 (after length indicator).
  
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Section 5 of field files is a stored walkmesh. A walkmesh is a mesh of polygons on which characters move, telling the engine for example how high it is, and using this the character can, for example, cross bridges with the real feeling that in the middle he is at a higher place than on the sides. It has very simple structure.  
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Section 5 of field files is a stored walkmesh. A walkmesh is a mesh of polygons on which characters move, telling the engine for example how high it is, and using this the character can, for example, cross bridges with the real feeling that in the middle he is at a higher place than on the sides. It has very simple structure.
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{| class="wikitable"
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! Offset
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! Name
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! Data Type
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! Length
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! Description
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|-
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| 0x0000
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| NoS
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| DWORD
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| 0x04
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| Number of Sectors
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|-
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| 0x0004
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| Sector Pool (SP)
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| DWORD
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| 24 * NoS
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| The data pool of Secots
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|-
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| 0x0004 + 24 * NoS
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| Sector Access Pool (SAP)
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| WORD[3]
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| 6 * NoS
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| ID of triangle of each Edge
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|}
  
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==== Section 5 Header ====
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==== Section 5 Header ====
  
 
Startofs 0x00 Length 0x04
 
Startofs 0x00 Length 0x04
  
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Walkmesh doesn't have header, it is only one 4 bytes long unsigned int, called NoS (Number of sectors).
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The walkmesh information is preceeded by a DWORD (4 bytes) unsigned int, named '''NoS''', short for the Number of Sectors in the walkmesh.
  
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==== Sector pool ====
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==== Sector pool ====
  
 
Startofs 0x04 Length NoS*24
 
Startofs 0x04 Length NoS*24
  
 
  typedef struct {
 
  typedef struct {
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     short x,z,y,res; // short is 2 bytes long integer
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     short x,y,z,res; // short is a 2 byte signed integer
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  } vertex_3s; // 3 short
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  } vertex_3s; // 3s == 3 short although there are 4 this is for 32 bit data alignment in PSX
  
 
  typedef struct {
 
  typedef struct {
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     vertex_3d v[3];
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     vertex_3s v[3]; // a triangle has 3 vertices
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  } sect_t;  
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  } sect_t; // Sector Type
  
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In sector pool are sectors, in fact just triangles and its position. For each sector you have three vertex_3s. Just store them. It seems that res and z are very often same, but not always, I don't know why. It seems that all polygons are clockwise. I didnt check it, but it is probably in order to know wheather point is in triangle. If you give it in other direction, point will be detected outside if it is inside and vice versa.
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The pool consists of sectors, which are in fact triangles, each with their vertices position. For each sector there are 3 vertices (3 vertex_3s). Res is always equal to v[0].z (it is just a padding value). The polygons are 'wound' clockwise, this makes determining if a point is within a triangle easier.
  
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==== Access pool ====
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==== Access pool ====
  
 
Startofs 0x04 + NoS*24 Length NoS*6
 
Startofs 0x04 + NoS*24 Length NoS*6
Line 33: Line 61:
 
  }
 
  }
  
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In access pool you have ID of poly, you should go into if you cross line.
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The access pool is an array of access data (ID's of triangles in the Mesh) in the mesh, the ID is the triangle you should be in if you cross that edge.
  
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acces1 is for line from vertex 0 to 1
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acces1 is for line from vertex 0 to 1 acces2 is for line from vertex 1 to 2 acces3 is for line from vertex 2 to 0
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acces2 is for line from vertex 1 to 2
 
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acces3 is for line from vertex 2 to 0
 
  
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If acces1/2/3 is FFFF then you are not allowed to cross this line. Acces pool and sector pool are same size (NoT), so you will just use same index for both pools. If access don't translate you, it just says, you should be here, if you are not, then there is a problem. If you design polymesh where you cross line and access tells you that you should be in poly 12, but you are god know where then FF7 stops.
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If the edge value is 0xFFFF, than this edge cannot be crossed (it's blocked). The access pool and sector pool have the same number of entries, thus you use the same index value for both pools of data to access the data for the same triangle. The access data merely informs one that if the PC object crosses this line the object should be in the indentified triangle. FF7 will halt running if you are not in the '''access''' specified triangle.

Latest revision as of 02:41, 13 July 2019

Section 5: Walkmesh (Kero)

File:180px-Field Wutai.jpg
Field Wutai.jpg
Wutai Walkmesh

Every every offset is here relative, 00 is at the start of section 5 (after length indicator).

Section 5 of field files is a stored walkmesh. A walkmesh is a mesh of polygons on which characters move, telling the engine for example how high it is, and using this the character can, for example, cross bridges with the real feeling that in the middle he is at a higher place than on the sides. It has very simple structure.

Offset Name Data Type Length Description
0x0000 NoS DWORD 0x04 Number of Sectors
0x0004 Sector Pool (SP) DWORD 24 * NoS The data pool of Secots
0x0004 + 24 * NoS Sector Access Pool (SAP) WORD[3] 6 * NoS ID of triangle of each Edge

Section 5 Header

Startofs 0x00 Length 0x04

The walkmesh information is preceeded by a DWORD (4 bytes) unsigned int, named NoS, short for the Number of Sectors in the walkmesh.

Sector pool

Startofs 0x04 Length NoS*24 

typedef struct {
   short x,y,z,res;		// short is a 2 byte signed integer
} vertex_3s;			// 3s == 3 short although there are 4 this is for 32 bit data alignment in PSX

typedef struct {
   vertex_3s v[3];		// a triangle has 3 vertices
} sect_t; 			// Sector Type

The pool consists of sectors, which are in fact triangles, each with their vertices position. For each sector there are 3 vertices (3 vertex_3s). Res is always equal to v[0].z (it is just a padding value). The polygons are 'wound' clockwise, this makes determining if a point is within a triangle easier.

Access pool

Startofs 0x04 + NoS*24 Length NoS*6 

typedef {
   short acces1,acces2,acces3;
}

The access pool is an array of access data (ID's of triangles in the Mesh) in the mesh, the ID is the triangle you should be in if you cross that edge.

acces1 is for line from vertex 0 to 1 acces2 is for line from vertex 1 to 2 acces3 is for line from vertex 2 to 0

If the edge value is 0xFFFF, than this edge cannot be crossed (it's blocked). The access pool and sector pool have the same number of entries, thus you use the same index value for both pools of data to access the data for the same triangle. The access data merely informs one that if the PC object crosses this line the object should be in the indentified triangle. FF7 will halt running if you are not in the access specified triangle.

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