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File formats

PMD (High-Speed Modeling Data)

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

PMD (High-Speed Modeling Data)
Extension.PMD
ID0x00000042

Overview

The PMD format is used for modeling data supported by the extended graphics library (libgs). PMD has a narrower range of functions than TMD, but this smaller scope enables faster processing. PMD handles only triangular and rectangular polygons. The data contains the areas in which packets are created, and polygons that have the same attributes are handled as groups.1

File Structure

A PMD file consists of a table of 3D objects along with their PRIMITIVE and VERTEX descriptions. VERTEX groups exist only when vertices are shared, so VERT POINT is 0 for a file of independent vertices. The fields are as follows:1

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

Coordinate values in a PMD file follow the 3D coordinate space of the 3D graphics library. The positive X axis points right, the positive Y axis points down and the positive Z axis points into the depth, and each coordinate is a signed 16-bit integer from -32768 to +32767.2

Vertices are stored as floating point values in the RSD format, so conversion from RSD to PMD converts and scales them as needed. The scale used is recorded in the object structure. However, the current version of libgs ignores the scale value.2

OBJ TABLE

The OBJ TABLE holds the pointers to the primitive groups of each object, because a single object is composed of primitive groups. NOBJ gives the number of objects. Each object then has an NPTR field followed by its pointers from POINTER 0 to POINTER (nptr-1).2

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

PRIMITIVE Group

A PRIMITIVE Gp is a group of graphics packets for the primitives of an object, and a single packet contains one primitive. PMD primitives differ from the drawing primitives handled by libgpu. When libgs functions apply the perspective transformation, they are converted to drawing primitives.2

Each primitive group opens with one word that holds TYPE and NPACKET. The packet data follows:3

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

The TYPE bits are laid out 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 packet data structure changes with the value of TYPE. However, bits 20 and 21 have no effect on it. Each structure holds a set of two drawing primitives for a double buffer, and the contents of both must be initialized in advance.3

Packet Data

The packet data structure for each TYPE value is shown below. In each structure pkt[] is the corresponding drawing primitive packet. With independent vertices v1 to v4 are the vertex coordinates, and with shared vertices vp1 to vp4 are offsets from the start of the row of shared vertices.345

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

VERTEX

The VERTEX group is an array of SVECTOR structures for shared vertices. VX, VY and VZ are the X, Y and Z coordinates of the vertex as 16-bit integers:5

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

References

  1. ^ a b Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-35, Figure 77.

  2. ^ a b c d Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-36, Figure 78.

  3. ^ a b c d Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-37, Figure 79 and Table 2-2.

  4. ^ Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-38.

  5. ^ a b Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-39, Figure 80.

Categories: File formats