PMD (High-Speed Modeling Data)

Modeling data for libgs that holds ready drawing packets for fast processing.

PMD (High-Speed Modeling Data)
Extension	.PMD
ID	0x00000042

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Overview

The PMD format holds modeling data for the extended graphics library (libgs).¹

PMD has fewer functions than TMD. The smaller scope allows faster processing.¹

PMD handles the following kinds of objects:¹

Triangular and rectangular polygons only
Packet creation areas contained in the data
Groups of polygons that have the same attributes

File Structure

A PMD file holds a table of 3D objects with their PRIMITIVE and VERTEX data.¹

The file has the following fields:

Table 1: PMD file structure
Field	Contents
ID	32-bit word with the version of the PMD file. The current version is 0x00000042.
PRIM POINT	32-bit offset of the PRIMITIVE Gp section from the start of the file
VERT POINT	32-bit offset of the VERTEX Gp section from the start of the file. 0 for independent vertices.
OBJ TABLE	The array of objects
PRIMITIVE Gp	Groups of polygons that have the same attributes
VERTEX Gp	Array of vertex coordinates, present only for shared vertices

Coordinate Values

PMD coordinates follow the 3D coordinate space of the 3D graphics library. Each coordinate is a signed 16-bit integer from -32768 to +32767.²

The positive X axis points right. The positive Y axis points down, and the positive Z axis points into the depth.²

Conversion from RSD to PMD scales the floating point vertex values as needed. The current version of libgs ignores the scale value.²

OBJ TABLE

The OBJ TABLE holds pointers to the primitive groups of each object. One object is made of primitive groups.²

The table has the following fields:

Table 2: OBJ TABLE fields
Field	Contents
NOBJ	Number of objects in the OBJ TABLE
NPTR	Number of pointers in one object
POINTER	Pointer to a primitive group

Each object has an NPTR field. Its pointers POINTER 0 to POINTER (nptr-1) follow.²

PRIMITIVE Group

A PRIMITIVE Gp is a group of graphics packets. One packet holds one primitive.²

PMD primitives differ from the drawing primitives of libgpu. libgs functions convert them to drawing primitives by perspective transformation.²

A primitive group opens with one word that holds TYPE and NPACKET.³

The word is as follows:

Table 3: Packet Gp header
Bits	Field	Contents
0..15	NPACKET	Number of packets
16..31	TYPE	Packet type

The TYPE bits are as follows:³

Table 4: TYPE bit layout
Bit no.	When 0	When 1
16	Triangle	Quadrilateral
17	Flat	Gouraud
18	Texture-On	Texture-Off
19	Independent vertex	Shared vertex
20	Light source calculation Off	Light source calculation On
21	Back clip	No back clip
22..31	Reserved for system	Reserved for system

The structure of the packet data depends on TYPE. Bits 20 and 21 do not change the packet data structure.³

Each packet holds two drawing primitives for a double buffer. Both must be initialized in advance.³

Packet Data

Each TYPE value has its own packet structure:⁴⁵

Table 5: Packet data structures
TYPE	Primitive	Structure	Members
00	Triangle, flat, texture on, independent vertex	_poly_ft3	POLY_FT3 pkt[2]; SVECTOR v1, v2, v3
01	Quadrangle, flat, texture on, independent vertex	_poly_ft4	POLY_FT4 pkt[2]; SVECTOR v1, v2, v3, v4
02	Triangle, Gouraud, texture on, independent vertex	_poly_gt3	POLY_GT3 pkt[2]; SVECTOR v1, v2, v3
03	Quadrangle, Gouraud, texture on, independent vertex	_poly_gt4	POLY_GT4 pkt[2]; SVECTOR v1, v2, v3, v4
04	Triangle, flat, texture off, independent vertex	_poly_f3	POLY_F3 pkt[2]; SVECTOR v1, v2, v3
05	Quadrangle, flat, texture off, independent vertex	_poly_f4	POLY_F4 pkt[2]; SVECTOR v1, v2, v3, v4
06	Triangle, Gouraud, texture off, independent vertex	_poly_g3	POLY_G3 pkt[2]; SVECTOR v1, v2, v3
07	Quadrangle, Gouraud, texture off, independent vertex	_poly_g4	POLY_G4 pkt[2]; SVECTOR v1, v2, v3, v4
08	Triangle, flat, texture on, shared vertex	_poly_ft3c	POLY_FT3 pkt[2]; long vp1, vp2, vp3
09	Quadrangle, flat, texture on, shared vertex	_poly_ft4c	POLY_FT4 pkt[2]; long vp1, vp2, vp3, vp4
0a	Triangle, Gouraud, texture on, shared vertex	_poly_gt3c	POLY_GT3 pkt[2]; long vp1, vp2, vp3
0b	Quadrangle, Gouraud, texture on, shared vertex	_poly_gt4c	POLY_GT4 pkt[2]; long vp1, vp2, vp3, vp4
0c	Triangle, flat, texture off, shared vertex	_poly_f3c	POLY_F3 pkt[2]; long vp1, vp2, vp3
0d	Quadrangle, flat, texture off, shared vertex	_poly_f4c	POLY_F4 pkt[2]; long vp1, vp2, vp3, vp4
0e	Triangle, Gouraud, texture off, shared vertex	_poly_g3c	POLY_G3 pkt[2]; long vp1, vp2, vp3
0f	Quadrangle, Gouraud, texture off, shared vertex	_poly_g4c	POLY_G4 pkt[2]; long vp1, vp2, vp3, vp4

pkt[] is the matching drawing primitive packet. v1 to v4 are the vertex coordinates.⁵

vp1 to vp4 are offsets from the start of the row of shared vertices.⁵

VERTEX

The VERTEX group is an array of SVECTOR structures for shared vertices.⁵

One structure is as follows:

Table 6: VERTEX structure
Word	Upper 16 bits	Lower 16 bits
0	VY	VX
1		VZ

VX, VY and VZ are the X, Y and Z coordinates of the vertex as 16-bit integers.⁵

References

^ ^a ^b ^c ^d Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-35, Figure 77.
^ ^a ^b ^c ^d ^e ^f ^g Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-36, Figure 78.
^ ^a ^b ^c ^d Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-37, Figure 79 and Table 2-2.
^ Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-38.
^ ^a ^b ^c ^d ^e Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-39, Figure 80.

Categories: File formats