Houdini 19.0 Nodes Geometry nodes Block Begin

Block Begin geometry node

The start of a looping block.

On this page
Since 14.5

See looping in geometry networks for general information on how to use this node and Block End.

Parameters

Method

Fetch Feedback

The node’s input is used as the output for the first iteration, but subsequent iterations use the output of the previous iteration (that is, the output of the Block End referenced in Block path) to create a feedback loop. This lets you apply the same set of nodes to a piece of geometry over and over.

Fetch Piece

At each iteration, the output is one “piece” from this node’s input. A piece is defined as all elements where partition attribute such as piece or name has the same value. The piece attribute name is set on the Block End in the Template attribute parameter. If no attribute exists, fetches each point or primitive (according to the Template class on the Block End).

Fetch Metadata

Creates an empty geometry with detail attributes containing information about the current loop. You would use this in a loop created by another Block Begin in “Fetch feedback” or “Fetch piece” mode, and then reference these attributes from inside the loop using the detail function.

See the looping documentation for how to use this.

Fetch Input

Copies the input. This is equivalent to just wiring directly past the block begin, but can sometimes result in a more semantically meaningful network.

Block Path

The path to the Block End representing the end point of this loop.

Reset Cached Pass

After cooking, this node caches the value it had in the last iteration. This lets you debug the last iteration by moving the display flag around inside the loop. Clicking this button clears the cache, so until the final node cooks again, this node show the initial state.

Create Meta Import Node

Create a separate node with metadata in detail attributes. You can access the attributes using the detail expression function. See looping in geometry networks for more information.

Inputs

Initial Geometry

When Method is “Fetch feedback”, this is the input to the first iteration. When Method is “Fetch piece”, this is the source of the pieces.

See also

Block Begin