LPM (Low Poly Model) 3D Format Documentation

Overview

The LPM format is a lightweight, human-readable format designed to store low-polygon 3D models. It supports vertices, normals, UVs, faces, and skeletal animations. Its simplicity makes it easy to parse and implement in custom tools.

Features

• Single texture per model
• Comments supported (lines starting with #)
• Compact and straightforward structure
• Skeletal animations support (optional)

Syntax

• Comments start with # and must be on their own line.
• Sections are identified by keywords (e.g., vertices, faces).
• Values within sections are comma-delimited, and they can include as many whitespaces as desired.
• The version and texture headers use a colon : followed by their values.
• Sections for bones, weights, and animation are optional for static models.

File Structure

An LPM file has the following structure:

version: 1

texture: cube.png

vertices

faces

bones

weights

animation

Sections

version

Specifies the version of the LPM format.

• Syntax: version: <number>
• Example: version: 1

texture

Specifies the texture file used for the model.

• Syntax: texture: <filename>
• Example: texture: cube.png

vertices

Defines the vertices of the model.

• Syntax: <x>,<y>,<z>,<nx>,<ny>,<nz>,<u>,<v>
  • <x>,<y>,<z>: Position of the vertex.
  • <nx>,<ny>,<nz>: Normal vector.
  • <u>,<v>: UV texture coordinates.
• Example:

  vertices
  -1.0, -1.0, -1.0,  0.0,  0.0, -1.0,  0.0,  0.0
   1.0, -1.0, -1.0,  0.0,  0.0, -1.0,  1.0,  0.0
  

faces

Defines the faces of the model as a list of vertex indices.

• Syntax: <v1>,<v2>,<v3>
• Example:

  faces
  0, 1, 2
  0, 2, 3
  

bones

Defines the skeletal hierarchy. (Optional for static models)

• Syntax: <bone_name>,<bone_id>,<parent_bone_id>, <head_x>, <head_y>, <head_z>, <tail_x>, <tail_y>, <tail_z>
  • <bone_name>: Name of the bone.
  • <bone_id>: Unique bone ID.
  • <parent_bone_id>: Parent bone ID (-1 for root).
  • <head_x>, <head_y>, <head_z>: Head coordinates of the bone in 3D space
  • <tail_x>, <tail_y>, <tail_z>: Tail coordinates of the bone in 3D space
• Example:

  # Bones: bone_name, bone_id, parent_bone_id, head_x, head_y, head_z, tail_x, tail_y, tail_z
  bones
  Hips, 0, -1, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0
  Spine, 1, 0, 0.0, 1.0, 0.0, 0.0, 2.0, 0.0
  

weights

Maps vertices to bones with associated weights. (Optional for static models)

• Syntax: <vertex_id>,<bone_id_1>,<weight_1>,<bone_id_2>,<weight_2>, ...
  • <vertex_id>: Index of the vertex in the vertices section.
  • <bone_id_n>: Bone ID from the bones section.
  • <weight_n>: Weight of the bone's influence (0.0 to 1.0).
• Example:

  weights
  0, 0, 1.0
  1, 1, 0.5,  0, 0.5
  

animation

Defines animation frames for bones. (Optional for static models)

• Syntax: <frame_id>,<bone_id>,<x>,<y>,<z>,<rx>,<ry>,<rz>
  • <frame_id>: ID of the frame
  • <bone_id>: ID of the bone.
  • <x>,<y>,<z>: Position of the bone.
  • <rx>,<ry>,<rz>: Rotation in radians.
• Example:

  animation
  # Frame 0
  0, 0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
  0, 1, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0
  
  # Frame 1
  1, 0, 0.0, 0.1, 0.0, 0.0, 0.0, 0.1
  1, 2, 1.0, 0.1, 0.0, 0.0, 0.0, 0.1
  

Parsing Rules

1. Comments (#) and empty lines are ignored.
2. Sections are terminated by the start of a new section or the end of the file.
3. Data within sections is comma-delimited, and they can include as many whitespaces as desired.
4. Section order:
   • version
   • texture
   • vertices
   • faces
   • Optional: bones, weights, animation

Example LPM File

# LPM: Low Poly Model
version: 1

texture: cube.png

# Vertices: x, y, z, nx, ny, nz, u, v
vertices
-1.0, -1.0, -1.0,  0.0,  0.0, -1.0,  0.0,  0.0
 1.0, -1.0, -1.0,  0.0,  0.0, -1.0,  1.0,  0.0
 1.0,  1.0, -1.0,  0.0,  0.0, -1.0,  1.0,  1.0
-1.0,  1.0, -1.0,  0.0,  0.0, -1.0,  0.0,  1.0

# Faces: vertex_1, vertex_2, vertex_3
faces
0, 1, 2
0, 2, 3

# Bones: bone_name, bone_id, parent_bone_id, head_x, head_y, head_z, tail_x, tail_y, tail_z
bones
Hips, 0, -1, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0
Spine, 1, 0, 0.0, 1.0, 0.0, 0.0, 2.0, 0.0

# Weights: vertex_id, bone_id_1, weight_1, bone_id_2, weight_2, ...
weights
0, 0, 1.0
1, 1, 0.5, 0, 0.5

# Animation frames: frame_id, bone_id, pos_x, pos_y, pos_z, rot_x, rot_y, rot_z
animation
# Frame 0
0, 0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
0, 1, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0

# Frame 1
1, 0, 0.0, 0.1, 0.0, 0.0, 0.0, 0.1
1, 1, 1.0, 0.1, 0.0, 0.0, 0.0, 0.1