Houdini Silhouette SOP v1.0 HDA

Extracts the silhouette of the input geometry as seen from an origin object (like a camera) or user-defined origin position.

The silhouette is projected in perspective (unlike SideFX Labs 'Extract Silhouette' HDA) onto the plane that passes through the center of the geometry bounding box.

In default mode, the silhouette always faces the origin object. The construction plane guide helps you visualize that. The plane center and normal are written out as detail attributes.

1. Uses VEX line-plane algebraic method (Unlike SideFX Labs 'Extract Silhouette' HDA)
2. Orthographic mode
3. Origin from oppath() or from world position vector parameter
4. Optional user-defined plane normal direction
5. World and Local space available for transformations
6. Output open or closed curve with curveu
7. Output curve frame (normal, tangent, and bitangent)

Tip: Use 'bitangent' to offset the silhouette curve inward or outward. Use smooth SOP on it if there are tight corners in the silhouette.