Repair polygonal models

Task	Operator
Consolidate points	Fuse.
Eliminate cracks	PolyStitch
Create a fill polygon between edges.	Curve tool ( snap the points of the polyline to the edges you want to fill, close the curve to create a face). PolyFill (fills holes with polygonal patches). PolyCap (select one edge of a loop to automatically fill the hole). TopoBuild (lets you interactively draw a reduced quad mesh automatically snapped to existing geometry).

Geometry

Working with objects
Primitives
Points and vertices
Geometry attributes

Describes how Houdini represents geometry using details, primitives, points, vertices, and attributes.
Groups
Volumes

Building terrain with height fields

How to use Houdini’s height field tools to generate realistic terrain.
Realistic terrain with heightfields

A heuristic workflow using the heightfield tools, based on experience generating realistic-looking terrain.

Import geometry from other objects
Create, edit, and use Null objects
Geometry appearance editor

The appearance editor mode of the data tree pane lets you edit various controls for object viewport/rendered appearance in one place.
Locking geometry nodes

Packed primitives
Looping in geometry networks
Compiled blocks

You can mark a chain of compilable SOPs as a compiled block which can execute much faster in parallel.
Programmatic geometry with verbs

Many geometry (SOP) nodes allow you to use them in Python scripts to generate geometry programmatically.
Primitive Parametric Spaces (Implicit UVs)
Speed vs. reproducibility in Math Kernel Library

Some nodes use a library that gives a speed boost for floating-point operations but can make the output vary between different computers. You can control how much the library tries to guarantee reproducible results.