Render nodes are “drivers” for rendering out the scene into various formats, often using external programs. For example, the mantra node uses mantra to render the scene, while the RenderMan node uses RenderMan.
Overview
Output driver nodes translate the scene into the format expected by a renderer and run the renderer on it. Houdini includes render drivers for the built-in mantra renderer, as well as RenderMan, other RIB renderers, and mental ray.
Output driver nodes live at the Render Outputs (ROP) level. They let you set up renders for different rendering methods, programs, and/or settings, and switch between them based on your needs at any given moment.
For example, you can set up different output nodes for different render qualities (such as test render and final render) and independent render passes. Or, you can render various scenes with different renderers.
Each driver renders the view of the scene through a camera . For a driver to work correctly, the camera associated with the driver must still exist.
Use Render > Create Render Node to create a new output driver.
Use Render > Edit Render Node to select and edit an existing render driver.
Note
Houdini’s shaders are specific to particular renderers. Rendering with a different renderer will require you to use different shaders on your objects. However, you can switch shaders based on the renderer .
How to temporarily disable outputs
ROPs have bypass flags and lock flags, which you can use to disable ROPs without disconnecting them from the network.
Bypassing a ROP will stop it from rendering. Input ROPs will still render.
Locking a ROP will stop it and all its input ROPs from rendering. This is a good way to 'lock off' a branch of renders. If some input ROP has another ROP that is dependent on it, and that ROP isn’t locked, it will still render. Locking a ROP will only block the one dependency path through the locked ROP.
Bypassing or locking a subnetwork will prevent any of the ROPs inside from rendering.
Tip
You can still force a bypassed or locked render node to render using the “Render All Bypassed Nodes” and “Render All Locked Nodes” options in the render control window.
Nodes
 | 3D Texture Generator | This output operator is used to drive the image3d program which generates 3D texture maps. |
 | Alfred | Alfred is a program shipped out with Pixar’s distribution of RenderMan. |
 | Archive Generator | Generates disk-based archives which can be used by either mantra or RIB renderers. |
 | Batch | Renders the input ROP in a single batch job. |
 | Channel | The Channel output operator generates clip files from a particular CHOP. |
 | Composite | The Composite output operator renders the image(s) produced in the Compositing Editor. |
 | DSM Merge | Merges two or more deep shadow/camera map files. |
 | Dynamics | Saves the state of a DOP network simulation into files. |
 | Fetch | Makes a dependency link to a ROP in a different network. |
 | Filmbox FBX | Exports entire scenes to FBX files. |
 | Frame Container | Prevents frame dependency changes in the contained nodes from affecting its inputs. |
 | Frame Depedency | Allows an output frame to depend on one or more input frames. |
| Geo to I3D | Converts .bgeo and .geo volumes into .i3d |
| Geometry | Generates geometry files from a SOP or DOP network. |
 | HQueue Render | HQueue, or Houdini Queue, is a distributed job scheduling system. |
| HQueue Simulation | HQueue, or Houdini Queue, is a distributed job scheduling system. |
 | MDD Point Cache | This output operator is used to write an MDD animation file. |
 | Mantra | Renders the scene using Houdini’s standard mantra renderer and generates IFD files. |
 | Merge | Merges several render dependencies into one. |
 | Net Barrier | Blocks the ROP network until synchronization occurs. |
 | Null | Does nothing. |
 | OpenGL | Render an image using the hardware-accelerated 3D viewport renderer. |
 | Pre Post | Renders ROPs before and after a main job. |
 | RenderMan | Renders the scene using Pixar’s RenderMan renderer. |
 | Shell | Runs an external command. |
 | Subnetwork | The SubNetwork output operator provides an easy way to manage large number of output operators. |
 | Switch | Renders one of several inputs. |
 | Torque | Exports the scene to the Torque DTS or DSQ format. |
 | Wedge | Re-renders the same ROP multiple times with different settings |
 | Wren | This output operator is used to drive the Wren rendering program. |
 | mental ray | Renders the scene using the mental ray renderer from mental images. |