PS1 Mesh Loader Example (using psyqo)

This is a practical example of how to load a 3D model from the CD-ROM on the original PlayStation using psyqo. It demonstrates:

• Loading a custom .meshbin model format from the CD-ROM
• Basic camera control and analog stick input
• Real-time rendering using fixed-point math and the GTE

This project was assembled from various psyqo examples, and camera logic was inspired by the psxsplash project. It aims to provide a real-world example of doing something meaningful with CD-ROM data streaming on the PS1.

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🔧 Requirements

• psyqo (included as a submodule)
  https://github.com/pcsx-redux/nugget/tree/main/psyqo

• mkpsxiso (for building the PS1 CD image)
  https://github.com/Lameguy64/mkpsxiso

Clone the repo with submodules:

git clone --recursive <this-repo>

🧱 Mesh Format: .meshbin

This example uses a custom binary mesh format (.meshbin) designed to be simple to parse on the PS1.

This is generated from a .obj exported from Blender at a scale of 0.125. For the sake of making it actually visible in the GTE, each vertex position is multiplied by 128. This presumes that 1m in blender is 128px on the PS1.

📦 Format Structure

The file is written in the following order (little-endian), using Python-style struct.pack() layout:

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🗂️ Header

Type	Description
uint32	Vertex count
uint32	Index count
uint32	Face count

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🧍 Vertex Positions

int32 x, y, z; // 3x int32_t per vertex

Vertex Colors

Note: This isn't implemented in this example

For each vertex paint colour make sure that 0=0, and 1.0 = 128. The PS1 does support up to 255, but 128 is the "neutral" colour, anything higher will make your vertex colour super bright.

For each vertex:

int16 r, g, b; // 3x int16_t per vertex

If no color data is provided, RGB values are set to -1.

Faces (Vertex Indices)

For each face:

int16 v0, v1, v2, v3; // 4x int16_t per face

Normals

Note: This isn't implemented in this example

Type	Description
uint32	Normal count

Then for each normal:

int16 x, y, z; // 3x int16_t per normal

Then for each face (normal indices):

int16 n0, n1, n2, n3; // 4x int16_t per face

UVs

Note: This isn't implemented in this example

Type	Description
uint32	UV count

Make sure that your UVs are multiplied by your texture size. So for example if your texture is 128x128px, then 0=0, 0.5=64, 1.0=128.

Then for each UV:

int16 u, v; // 2x int16_t per UV

Then for each face (UV indices):

int16 t0, t1, t2, t3; // 4x int16_t per face

ISO Image

Use mkpsxiso to pack your disc image, following standard PS1 CD-ROM structure. See the cdrom directory for more information on this.

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🎮 Controls

• Left Analog Stick — Move forward/backward/left/right
• Right Analog Stick — Rotate camera
• Triangle / Cross — Additional forward/back movement
• Square / Circle — Additional left/right movement
• L1 / R1 — Move camera up/down

Deadzone handling and fixed-point scaling are used to make input smoother and less sensitive.

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📝 License

This project is licensed under the MIT License. See the LICENSE file for details.