granny1-parser

A standalone parser and glTF converter for RAD Game Tools Granny 1 (.grn) files — the 3D asset format behind AWE Games' 2002 Nickelodeon titles, and the one Granny generation that had no public parser until now: Granny 2 (.gr2) has several community readers; Granny 1 had none, so every game that shipped on it carried unreadable meshes, skeletons and animations unless you ran RAD's own non-redistributable, 32-bit-Windows-only runtime.

• grn.py — the parser. One file, Python 3, standard library only: drop it into your project and read .grn files. A real API first (objects, skeleton, meshes, skinning, materials, animations), a CLI on top.
• grn2gltf.py — the converter, built on the parser: skinned, animated glTF 2.0 (.glb) plus OBJ export, with the coordinate-system decisions documented rather than baked in.
• SPEC/GRN-V1.md — the format specification the parser is written against, claim by claim, each with the corpus count it was validated on and the oracle it rests on.
• tools/validate.py — every structural check in the spec, runnable over a directory of files.

Validation

corpus	files	result
SpongeBob SquarePants: Employee of the Month (2002)	674	674 pass
Jimmy Neutron vs. Jimmy Negatron (2002)	389	389 pass

The mesh layer is additionally verified corner-by-corner against a live capture of RAD's own runtime decoding the same files: positions, normals, texture coordinates and triangle order all match exactly (SPEC §13).

Use

python grn.py SB_Model.grn                     what is in the file
python grn.py SB_Model.grn --skeleton          bones, parents, names
python grn.py SB_Model.grn --objects           named objects + properties
python grn.py SB_Model.grn --tree              the raw record tree

python grn2gltf.py SB_Model.grn -o sb.glb
python grn2gltf.py SB_Model.grn --anim SB_walk.grn --anim SB_Idle1.grn -o sb.glb
python grn2gltf.py SB_Model.grn --texture sponge=sponge.png -o sb.glb
python grn2gltf.py SB_Model.grn --obj sb.obj

python tools/validate.py <directory of .grn files>

import grn
f = grn.parse("SB_Model.grn")
f.bones[2].name                  # 'Bip01 Pelvis'
f.meshes[0].positions[0]         # (-31.4856, 16.6441, 57.9688)
f.animation.tracks[0].name       # the node a track drives

No game assets are included, and none are needed to use the code — bring your own copy of a game that ships .grn files.

Textures

Model files embed their textures, but compressed with RAD's own codec (FourCC BIKi). This project deliberately reads the header and stops: reproducing a proprietary codec is a materially different act from documenting a container, and PROCESS.md draws that line on purpose. The same art ships in the games' .omt containers in decodable form (see awefan's published OMT toolkit); grn2gltf.py --texture binds an image recovered that way.

Provenance

Everything in the spec was derived from the data files by measurement, and validated corpus-wide; no function of granny.dll is described, listed or reproduced anywhere in this repository. The full reverse-engineering record — method, wrong turns and all — lives in the sibling repository grn-re, and a working showcase with converted assets at https://exentt.com/grn/.

An Exentt Systems project — https://exentt.com/.