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HMD (Hierarchical 3D Model and Animation Data): Difference between revisions

Revision as of 02:22, 23 October 2026
RemmyLee
(Hardware and system software pages from the Sony manuals)		Revision as of 02:27, 23 October 2026
RemmyLee
(File format pages from the Sony File Formats manual)
Line 1:Line 1:
+---
+title: HMD (Hierarchical 3D Model and Animation Data)
+type: format
+summary: Integrated format for model and image and animation data.
+category: File formats
+info: Extension = .HMD
+info: Version ID = 0x00000050
+info: Library = libhmd
+---
+
+## Overview
+
+HMD is a generic graphics format. Model data, texture data and animation data are handled within one framework.[^ff249]
+
+HMD is extended to new kinds of data through a unique identification code called a type.[^ff249]
+
+A program that plays back HMD data is called a primitive driver. Primitive drivers are linked to HMD data through their type.[^ff249]
+
+Sony Computer Entertainment made a set of standard primitive drivers for libgs. The drivers have standard interfaces, so users and middleware companies can write their own.[^ff249]
+
+The HMD format is supported by Library Version 4.0 and later.[^ff249]
+
+Up to library 4.2 the HMD functions were part of libgs and libgte. They are now in the separate library libhmd. Its header file is libhmd.h.[^ff249]
+
+The environment map was a beta version in this release. Its format could change.[^ff249]
+
+## Structure
+
+HMD data has two main parts:[^ff249]
+
+- The HMD header
+- The HMD body
+
+The HMD body is made of sections. The primitive section and the primitive header section are always required.[^ff249]
+
+Other sections are present only when the type needs them. A model can also have a coordinate section.[^ff249][^ff250]
+
+### Pointers
+
+Pointer values are converted into real memory addresses at run time. This step is called mapping, and GsMapUnit() performs it.[^ff250]
+
+HMD data can be used only after its addresses are mapped.[^ff250]
+
+The initial value of a pointer is a count of 32-bit words from the top of the HMD data.[^ff250]
+
+### HMD Header
+
+The HMD header holds the following fields:[^ff250][^ff251]
+
+Table: HMD header section
+
+| Field | Contents |
+| --- | --- |
+| Version ID | 0x00000050 |
+| MAP FLAG | 1 after GsMapUnit() has mapped the data, otherwise 0 |
+| Primitive header section pointer | Start of the primitive header section |
+| Number of blocks | Number of primitive block pointers |
+| Pointer to the primitive block 0..n | One pointer for each primitive block |
+
+GsMapUnit() reads and changes MAP FLAG.[^ff251]
+
+## Primitives
+
+The primitive section is a collection of primitive blocks.[^ff251]
+
+A primitive block is a chain of one or more primitives. Pointers join the primitives of the chain.[^ff251]
+
+A primitive has a control section and one or more data sections.[^ff251]
+
+The parts are as follows:
+
+Table: Primitive structure
+
+| Part | Field | Contents |
+| --- | --- | --- |
+| Control section | Next Prim pointer | Header of the next primitive in the chain. 0xFFFFFFFF ends the chain. |
+| Control section | Primitive header pointer | The primitive header of this primitive |
+| Control section | Type count | Number of data sections. The MSB is 1 while the pointers are unmapped and 0 after mapping. |
+| Data section | type | Identifier of the data |
+| Data section | Data count / size | Upper 16 bits: number of data sets. Lower 16 bits: size of one data section in words. |
+| Data section | Data | The data, in a format set by type |
+
+### SCAN
+
+A SCAN overwrites each type field with the start address of its primitive driver.[^ff252]
+
+GsScanUnit() finds the address and value of the type field of each primitive. The driver address can then be written into the type field.[^ff252]
+
+Changing the value of type changes the meaning of the data and its driver.[^ff252]
+
+### Primitive Header
+
+The primitive headers are grouped in the primitive header section. The HMD header points to that section.[^ff252]
+
+There is one primitive header for each primitive block. Its first word is its size in words, and pointers to the sections follow.[^ff252]
+
+A word with the MSB set is a pointer to a section.[^ff252]
+
+A word with the MSB clear is a numeric value. It can serve as a parameter to the primitive driver.[^ff252]
+
+## Type Field
+
+The type field is 32 bits in four parts:[^ff260][^ff2131]
+
+Table: Type field
+
+| Bits | Field | Contents |
+| --- | --- | --- |
+| 28..31 | DEVELOPER ID | ID of the developer of the format. 0x0 is SCE, 0xf is user defined. |
+| 24..27 | CATEGORY | Category of the data |
+| 16..23 | DRIVER | Bits that change the behavior of the primitive driver |
+| 0..15 | PRIMITIVE TYPE | Bit assignment depends on the primitive type |
+
+A developer with a unique ID can use the other bits freely.[^ff260]
+
+The categories are as follows:[^ff260][^ff2128][^ff2131]
+
+Table: HMD categories
+
+| Category | Data |
+| --- | --- |
+| 0 | Polygon data |
+| 1 | Shared polygon data |
+| 2 | Image data |
+| 3 | Animation data |
+| 4 | MIMe data |
+| 5 | Ground data |
+| 6 | Pseudo-environment map (beta, library 4.2) |
+| 7 | Device primitives (camera and light) |
+
+The manual gives the type 0x00100008 as an example. It is developer SCE, category CTG_POLY, driver bit BOT (double-sided) and primitive type TRI (triangle).[^ff2131]
+
+The name of the driver function is "GsU_" followed by the bit pattern.[^ff2131]
+
+## Categories
+
+### Model Data (Category 0)
+
+Model data must have the HMD header, primitive header, coordinate, primitive, polygon and vertex sections. It can also have normal and image sections.[^ff253]
+
+Each coordinate system of a model is assigned to its own primitive block.[^ff253]
+
+The DIV bit of the polygon driver enables polygon subdivision. The FOG bit turns fog on.[^ff261]
+
+### Shared Primitives (Category 1)
+
+Shared primitives use two kinds of driver: PRE-CALCULATION drivers and shared drivers.[^ff290]
+
+A PRE-CALCULATION driver converts a 3D shared vertex array into a perspective-transformed 2D vertex array. For normals it calculates vertex colors.[^ff290]
+
+A shared driver takes the calculated vertices and builds GPU packets into the OT. It is chained to the POST-PROCESS primitive block so that it runs last.[^ff290]
+
+### Image Data (Category 2)
+
+HMD can hold image data as a primitive. Model, image and animation data can then be managed together.[^ff292]
+
+Image data can also stay outside HMD in [TIM](/formats/tim/) files.[^ff293]
+
+### Animation Data (Category 3)
+
+An animation primitive section has five subsections:[^ff295]
+
+- Animation primitive header section
+- Sequence pointer section
+- Interpolation function table section
+- Sequence control section
+- Parameter section
+
+### MIMe Data (Category 4)
+
+The MIMe primitive is described in the libgs reference. The MIMe types are joint MIMe and vertex or normal MIMe. Each type also has a reset form.[^ff2118]
+
+### Ground Data (Category 5)
+
+A ground primitive generates packets at run time from the width and height of a grid and the number of grids.[^ff2125]
+
+This method reduces the amount of HMD data.[^ff2125]
+
+### Device Primitives (Category 7)
+
+Device primitives hold camera (viewpoint) and light (light source) settings that applications used to make in code.[^ff2128]
+
+Camera primitives set the projection and the camera position and direction.[^ff2128]
+
+## References
+
+[^ff249]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-49.
+[^ff250]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-50, Figures 98 and 99.
+[^ff251]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-51, Figures 100 and 101.
+[^ff252]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-52, Figure 102.
+[^ff253]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-53.
+[^ff260]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-60, Figure 107.
+[^ff261]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-61, Figure 108.
+[^ff290]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-90.
+[^ff292]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-92.
+[^ff293]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-93.
+[^ff295]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-95.
+[^ff2118]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-118.
+[^ff2125]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-125.
+[^ff2128]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-128.
+[^ff2131]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 2-131.