Houdini VFX Knowledge Base

Files

File	Description
coin-transformation-diagram.excalidraw	Node diagram for 3-stage coin transformation (open at excalidraw.com)
houdini21_coin_3stage_transformation_tutorial.md	Full tutorial: 3-stage coin object morph with guide curves, falloff, stacking
houdini21_instance_morphing_research.md	Raw research: H21 SOPs, VEX functions, matching strategies, APEX analysis

Key Concepts

Object-to-Object Coin Transformation

• Scatter points on source and target meshes (Force Total Count = same)
• Match points (nearpoint, sort-based, or shuffled)
• 3-phase flight: Source -> Guide Curve -> Target
• Falloff-driven stagger (object proximity or noise)
• Coin stacking for different-sized objects (offset along N)
• APEX is NOT suitable for this -- use SOPs + VEX

Critical H21 SOPs

• Scatter v2.0, Copy to Points v2.0, Attribute Sort (NEW), Separate Pieces (NEW)
• Path Deform SOP for curve following
• Point Jitter SOP now has mask parameter

VEX Essentials

• Always use orient quaternion for animated instances (not N/up)
• lerp for position, slerp for orientation
• primuv() for sampling guide curves
• dihedral({0,0,1}, N) to convert normals to quaternion
• sin(blend * PI) for guide_weight that peaks mid-flight