Lego Rendering Pipeline

Render semi-realistic, individual parts. Primarily used to train machine learning models for detection, part classification and color classification.

This uses LDraw's part models and Blender to produce a render.

A single render typically takes 10-15s on an M1 Pro. There is a draft mode that takes a few seconds.

Parts

In theory this can render any LDraw part. However I've only tested with typical plastic Lego parts. Parts are specified using their LDraw ID. In many cases this will be same as the mold number on the part but not always. Keep in mind there may be multiple molds over time.

Materials

Currently supports plastic, transparent and rubber. Not supported yet: pearlescent, glitter, neon colors, metal and cloth.

Colors

Colors are specified with hex codes in sRGB. Included is a list of named colors from Rebrickable.

Rotation

Parts can be rotated to various angles. The parts are moved up/down to remain touching the ground.

Lighting

Lighting Styles: default, bright, hard

Lighting angle around the part

Camera

Camera height: degrees from 0-90

Camera zoom

Instruction Look

By default they are rendered with a transparent background. Use PNG format (format=Format.PNG).

Setup

• Install Blender
• Download ImportLDraw Plugin
• LDraw parts library
  • download the complete zip
  • extract into ./ldraw, e.g. ./ldraw/parts/30010.dat
• LDraw unofficial parts
  • download all Unofficial Files
  • extract into ./ldraw/unofficial, e.g. ./ldraw/unofficial/parts/22388.dat
• Run

  ./setup.sh
  

Run

Build script:

renderer = Renderer(ldraw_path="./ldraw")

renderer.render_part("6126b", RenderOptions(
    image_filename = "renders/test.jpg",
    part_color = RebrickableColors.Blue.value.best_hex,
    material = Material.PLASTIC,
    lighting_style = LightingStyle.BRIGHT,
    light_angle = 160,
    part_rotation = (0, 0, 270),
    camera_height = 45,
    zoom = 0.1,
    look = Look.NORMAL,
    width = 244,
    height = 244,
))

See lib/renderer/render_options.py for the full list of options. See docs-*.py to see how the images on this page were genereated.

Run in Blender's Python environment:

./run.sh test.py         # renders to renders/test/png

./run-watch.sh test.py   # run test.py each time a .py file is saved