TECHNICAL PAPER Building Tools for Houdini 9

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IconHoudini library or custom?HandlesHandles to be provided for the userToolBoxParameters to be exposed in the viewport tool boxLike ToolsResourcesAny existing tools with similar functionality that might provide a good usage model or starting pointReferencesSources to aid development e.g. images, papersBuild the Digital AssetDevelop the underlying networks as you would for any asset. We will not cover this process here – refer tothe online Help and Tutorials as necessary.Create Digital Asset and pay attention to how the asset is named. We suggest following nomenclature:Digital Asset name: format will be lower case with underscores in place of spaceseg: rbd_simpleDigital Asset label: format will be capitalized version of “name” with spaces allowedeg: RBD Simpleotl file: will prefix the “name” with “category”eg: FX_rbd_simple.otlOperator Type Properties defaults and settingsThe Edit Operator Type Properties dialog contains many settings that need to be managed. Here wediscuss a few of the most important.Basic Folder1.2.The Hide default Parameters option is usually checked on for object level assets. This hides the toplevel subnet Transform and Subnet folders. If the top level Transforms need to be accessed you caneither uncheck this option or create new parameters that are referenced in to the hidden defaultparameters.Turn off Save Defaults as initial Parameters if you wish to capture the state of any and all parametersand folder settings in the asset interface. Otherwise leave it on to force the parameter defaults to beused when the asset is placed. When off, you can change the top level parameters to values off theirdefaults plus switch to different folder views and have that captured as the initial state when the toolis placed.As an example, if you want your tool to always show a particular folder other than the first top levelfolder and change some default values in the parameters when initially placed in the scene, simplyturn this option off and configure the parameters and folders for the current edited asset appropriatelythen press Apply or Accept. The next time the asset is placed in a scene, the captured folderand parameters will be reproduced.14 | TECHNICAL PAPER Rev 1.0
Parameters Folder3.The Gear Menu allows you to set a number of useful preferences. Generally speaking it will savetime in naming and labeling parameters if Prefix Linked Parameter Name with Source NodeName and Prefix Linked Parameter Label with Source Node Label are OFF. Remember tofollow this action with Save Options as Default.Figure 12 -Gear Menu options4.The Linked Channels fields for parameters in the Parameters/Channels folder should be used tomanage the channel references. You can enter any number of internal channel references as a spacedelimited string of paths to the appropriate target parameters. Only straight channel references aresupported. It is recommended that you use the Linked Channel strings as a way of ensuring straightchannel references. If the target parameters have a complex expression that contains a ch(), chs()or any other type of channel reference to the top level asset parameter interface, then this referencewill not show up in the Linked Channels field and can be safely ignored.Use the arrow menu to the right of the Linked Channels field to manage this field. To update any internalchannel references, choose the option “Reset current links for this channel” or “Reset currentlinks for all channels“ to update all the channels represented by the selected parameter(s).Disable the Linked Channels reference when you are finding that channel references are unexpectedlydisappearing due to workflow issues.5. In Parameters/Import you can automatically import folders from operators one level below to toplevel Asset Folders by enabling the Save import information option. To fetch a folder labeled Setupfrom a contained object called my_embedded_obj do the following: set the Source field to my_embedded_obj:Setupand the Token to folder_name:Setup where folder_name is the Name field stringfor the folder labeled Setup on the target object. Additionally you can use the Mask field along withwild cards to only import subsets of channels from the referenced folder.Promote ParametersThere are no hard-written rules on how to organize or name an asset’s parameters and components. Howeverwe would like to encourage a consistent approach so the user can carry as much learned experience as possiblefrom using one asset to the next.For the FX Tools we organized parameters according to workflow and frequency of use.▪▪Folders (left to right) deal with Setup, Behavior (from gross animation parameters through tweaking),Look (Render) and Display (Viewport options)Building Tools for Houdini 9 | 15
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Page 5 and 6: 2.What are Tools and how are they u
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TECHNICAL PAPER Building Tools for Houdini 9

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