This document briefly describes the .tmd file format as used by the Sony
Playstation to store 3d object information.
This document is not intended to be distributed outside of the Net Yaroze 
community.

Please be aware that I have spent very little time working on this and the
source. Not all of the polygon primative structures are complete.  Once I 
completely understand them I will document them.  

If you have any comments or additions to make please contact me.

Written By James Pitts.  26/3/97. First Version.
sigill@geocities.com
http://www.playstaion.co.uk/~Sig1LL



-====-
HEADER
-====-


A .tmd file has a header starting at the very first byte of the file.

	offset	type
	
	0	ID
	4	Flags
	8	Num
	
	
	ID	Always 0x00000041
	Flags	Set to 1 if processed by GsMapModelingData(), else 0
	Num	Number Objects in tmd
	
	
This structure only appears once and is directly followed by the
first Object Header.

-===========-
Object Header
-===========-

This header describes each object in the tmd file.  All file offsets within
this object are taken from this point.

	offset	type
	0	Vertices Table
	4	Number Vertices
	8	Normal list Offset
	12	Number Normals
	16	Polygon Primatives Offset
	20	Number Primatives
	24	scaling	(aparently unused)
	
	The "Vertices Table" points to a table of vectors (see below for
	detail) with "Number Vertices" elements.  This is the x,y,z coord for
	each point in the object.
	
	Normals are store identically to the Vertices but obviously contain
	normal vectors.
	
	The Polygon Primatives describe each polygon in the scence ( 3 and 
	4 sided) these records have varying sizes.
	
-==================-
Vertices and Normals
-==================-


	To read the Vertice and Normal Data just seek to the offset specified
	in the Object Header structure.  Remember to add the tmd header size
	to the offsets. 
	
		NormalTab = ObjHead->NormalOffset + sizeof (tmdheader);
		
		
	The Vertices and Normal are just vectors.
	
	offset	type
	0	x
	2	y
	4	z
	6	filler
	
	
	filler is just for alignment padding and has no use.
	
-========-
Primatives
-========-

	This is where the fun starts. :-)
	
	This is a table of all the polygons in this object.
	Each polygon has a header, which is followed by a 
	variable size data block.
	
	Header.
	
	offset	type
	0	unknown
	1	data block length
	2	flag
	3	mode
	
	'data block length'  is the size of the data to follow this header
	measured in words.
  	If your reader does not understand the following data or wishes to
	ignore it.  It can just skip 'length * 4' bytes.
	
	The data to follow can be determined by the mode and flags fields.
	
	The Mode and Flags fields are both split into bitfields.  
	
	MODE.
	
	bits  	hex	type
	0	1	Brightness
	1	2	Transparency
	2	4	Texture
	3	8	Quad
	4	10	Gouraud
	5	20	1
	
	Bit 5 of the mode field is always 1.
	
        bit 0 == 1	No flat shading
	bit 1 == 1	Transparency On
	bit 2 == 1	Polygon Textured
	bit 3 == 1	4 sided polygon
	bit 4 == 1	Polgon is Gouraud shaded
	bit 5 == 1	Always 1.
	

	FLAG.
	
	bits	hex	type
	0	1	Light Source 
	1	2	2 Sided
	2	4	Gradation
	
	bit 0 == 1	Do not calculate light sourcing
	bit 1 == 1	Polygon is double sided
	bit 2 == 1	Gradated
	
	The structure that follow below are the data blocks for each 
	polygon mode.
	
		
*   Mode == 0x20 && Flag == 0 (Flat Shaded triangle)
    
    	offset	type
	0	red
	1	green
	2	blue
	3	filler
	4	index into normal table
	6	first point
	8	second point
	10	third point
	
    The rgb fields specify the ambient colour of the poly.
    
    Next is the offset in to the normal table for this 
      polygons Normal Vector.
      
    Followed by three indexes into the vertex table for 
      each point of the poly.
      
      
	
*   Mode == 0x28 && Flag == 0 (flat shaded Quad)
    
      Same as Mode == 0x20 structure except it has an extra point field
      followed by a 2 byte filler.
      
      offset	type 
      12	fourth point
      14	filler
      
      
     
*   Mode == 0x30 && Flag == 0 (Gouraud shaded Triangle)

	
    
    	offset	type
	0	red
	1	green
	2	blue
	3	filler
	4	index into normal table
	6	first point
	8	index into normal table
	10	second point
	12	index into normal table
	14	third point
	
	This is similar to the flat shaded polygon primatives except
	each vertice has an associated normal.
    	
*   Mode == 0x38 && Flag == 0 (Gouraud shaded Triangle)

      Same as Mode == 0x30 structure except it has an extra normal and
      point field.
      
      	offset	type
	16	fourth point normal
	18	fourth point
	
	
***************
END