Houdini 20.5 - Procedural Asteroids: TOPS to USD

In this tutorial we will explore how to take files from disk such as a collection of procedurally generated asteroids using TOPS and process them by applying poly reduction and automatic UV mapping. From there, we’ll bake out standard PBR maps as well as custom maps. Finally, we’ll convert everything into a USD asset, complete with geometry and material variants. To wrap it up, we’ll integrate our newly created asset into a quick lighting setup for demonstration.

Preview👇

Tutorial👇

Project Overview

• Goal: Procedurally generate and render realistic asteroid assets in Houdini using SOPs, MaterialX, and USD.
• Designed for rapid iteration, rendering, and variant testing — suitable for lookdev, layout, or background assets.

Procedural Generation Workflow

• Built using Houdini SOPs, starting from a base sphere.
• Uses attribute-based deformation:
  
  • Soft transforms
  • Noise modifiers (e.g., unified noise, mountain, remesh)
  • Boolean operations for cuts/fractures
  • Layers of detail added through multiple deform passes and topology tweaks.

USD Variant System

• Geometry variants created for:
  
  • Different asteroid shapes
  • Optional fractured states
  • High- and low-res proxy versions (via polyreduce)

MaterialX Shader Setup

• Procedural materials driven by geometry attributes (e.g., curvature, noise masks).
• Uses height map generation in COPs or live geometry displacement.
• Displacement and diffuse layers separated for better realism and export flexibility.

Turntable & Camera Rig

• Turntable setup using expression-driven spin controls.
• Viewport camera constrained to asset origin with optional zoom and pan.
• Can preview asset lighting and displacement under motion.

Rendering with TOPs

• Fully automated rendering pipeline using TOPs:
  
  • Renders multiple shape/material combinations.
  • Switches render settings (e.g., high-res for beauty, low-res for preview).
  • Saves to versioned folders with structured naming.

Lookdev & Lighting

• Supports light rig rotation for inspecting surface detail and form.
• Setup to test different lighting conditions using environment HDRIs.
• Scene can be cached or referenced for performance.