# Precomp node¶

This documentation is for version 1.0 of Precomp (fr.inria.built-in.Precomp).

## Description¶

The Precomp node is like a Group node, but references an external Natron project (.ntp) instead.

This allows you to save a subset of the node tree as a separate project. A Precomp node can be useful in at least two ways:

It can be used to reduce portions of the node tree to pre-rendered image inputs. This speeds up render time: Natron only has to process the single image input instead of all the nodes within the project. Since this is a separate project, you also maintain access to the internal tree and can edit it any time.

It enables a collaborative project: while one user works on the main project, others can work on other parts referenced by the Precomp node.

## Inputs¶

Input Description Optional

## Controls¶

Parameter / script name Type Default Function
Project Filename (.ntp) / projectFilename N/A   The absolute file path of the project to use as a pre-comp.
Edit Project… / editProject Button   Opens the specified project in a new Natron instance
Pre-Render / preRender Boolean On
When checked the output of this node will be the images read directly from what is rendered by the node indicated by “Write Node”. If no Write is selected, or if the rendered images do not exist this node will have the behavior determined by the “On Error” parameter. To pre-render images, select a write node, a frame-range and hit “Render”.

When unchecked, this node will output the image rendered by the node indicated in the “Output Node” parameter by rendering the full-tree of the sub-project. In that case no writing on disk will occur and the images will be cached with the same policy as if the nodes were used in the active project in the first place.
Write Node / writeNode Choice   Choose here the Write node in the pre-comp from which to render images then specify a frame-range and hit the “Render” button.
First-Frame / first Integer 0 The first-frame to render
Last-Frame / last Integer 0 The last-frame to render
On Error / onError Choice Error
Indicates the behavior when an image is missing from the render of the pre-comp project
Render / render Button