TECHNICAL PAPER Building Tools for Houdini 9

2.What are Tools and how are they used?This document defines tools as items that exist on the Shelf or in the TAB Menus. In their most basic incarnationtools are python scripts that perform actions when a button on the Shelf is pressed or when an item isselected from a TAB Menu in any of the contexts that support them.All operators in Houdini are now defined as tools. A tool can perform a function as simple as placing a singlenode or changing a node’s parameters. It can be as complex as placing multiple Digital Assets based onprompted input from the user.Some Examples are:Scripts that...▪▪▪▪▪▪▪▪Place new nodesModify existing nodesModify or create workspacesControl aspects of a pipelineNodes created using...▪▪▪▪▪▪Digital Assets (e.g. the Auto Rig nodes)VEX code (e.g. the Mountain SOP)HDK programmingCharacteristics▪▪▪▪▪▪Every tool has a python wrapper script that defines the way it behavesTools know what context they’ve been invoked from and can adjust their behavior accordingly.Tools know what to work on based on selections. Status information available to a tool includes:○○ The current operator (furnishes information about node type and parenting)○○ A list of the selected nodes, objects, or components○○ The current viewport and desktopWhere are Tools Found?While tools can be used from a wide variety of contexts including the Main Menus, RMB Menus, the shell andcmd files, and bound to Hot Keys, we are limiting our scope here to the two main contexts most used by artists,namely the Shelf and TAB MenusOn the ShelfFigure 1 - Each of these icons represents a toolHoudini ships with many predefined shelves each of which consists of a set of tools with related functionality.Many of these are “automatic” tools – i.e. their behavior is limited to placing a node. However there are alsogood examples of more complex tools that prompt the user for interaction and build node trees. The user canmodify these existing tools or add new ones, as well as reconfiguring the contents of the shelves.Building Tools for Houdini 9 | 5