Viewer

The Viewer node displays the render output of any connected process nodes in the Viewer panel. It doesn’t alter data in any way, but simply allows you to view the effect of any changes you make upstream.

You can place as many Viewer nodes in a script as you wish, which allows you to simultaneously view multiple outputs. You can also connect the output from up to ten process nodes into single Viewer node, and then cycle through the various displays. This allows you to easily compare an image before and after processing by a given effect.

You can also create this node by:

selecting Image > Viewer from the Nuke Toolbar, or

pressing Ctrl/Cmd+I.

Inputs and Controls

Connection Type

Connection Name

Function

Input

unnamed

The process node upstream to output to the Viewer. You can connect up to ten (0-9) nodes at once.

Control (UI)

Knob (Scripting)

Default Value

Function

Viewer Tab

frame_range

frame_range

none

Sets the first and last frame in the playback range. You can enter frame numbers here or Cmd+drag the red triangles in the timeline.

frame_range_lock

on

Click to unlock or lock playback to the frame numbers specified in frame_range.

<< >>increment

frame_increment

10

Sets the number of frames to step through using the Viewer << and >> buttons.

channels

channels

rgba

Sets the channels to display in the viewer.

You can also select a channel from a different layer to display in the alpha channel.

clip_warning

clip_warning

no warnings

When set to exposure, any pixels that are outside the 0-1 range are Zebra-striped in the Viewer.

gain

gain

1

Sets the amount of gain to multiply the image by before display.

gamma

gamma

1

Sets the amount of gamma correction to apply to the image.

Gamma correction is applied after the gain, viewerprocess, and any custom inputprocess.

apply LUT to color channels only

rgb_only

off

When enabled, the LUT is applied to color channels only.

downrez

downrez

1

Sets the amount of down scaling applied before display. factor to speed up rendering.

You can use downrez to speed up rendering, but bear in mind that it is multiplied into any global proxy scale that may also be in effect.

ignore pixel aspect

ignore_pixel_aspect

off

When enabled, output to the Viewer ignores the file’s pixel aspect ratio and always draws using square pixels.

prevent auto zoom

zoom_lock

off

When enabled, the Viewer is prevented from automatically adjusting the zoom level to fit new images into the Viewer when swapping between different sized images.

show overscan

show_overscan

off

When enabled, any overscan present is displayed in the Viewer.

enable full frame processing

full_frame_processing

off

When enabled, force Nuke to render every scanline in the image. Compared to the default mode, this may take slightly longer initially and requires more space in the Viewer cache, but once Nuke has cached the frames you require, you can pan around and change the zoom level without breaking the cache or affecting playback.

overscan

overscan

100

Sets the amount of overscan to show in the Viewer when show overscan ins enabled.

safe zone

safe_zone

no guides

Sets the safe zone overlay to apply to the image:

no guides

title safe

action safe

format center

format center

format_center

off

When enabled, the center of the format is marked with a cross in the Viewer.

mask region outside ratio

masking_ratio

square

Sets the aspect ratio of the mask specified in the mask mode dropdown.

mask mode

masking_mode

no mask

Sets the mask overlay to apply to the image:

no mask

lines

half

full

center f-stop

center_fstop

8

Sets the f-stop to display when gain is set to 1. You can use zero to show stops as +/-n.

Note:  If you want a non-integer value, enter a formula to get an accurate value, otherwise the display does not round to normal f-stop names. For instance, instead of 5.6 you would use pow(2,2.5) to get 5.65685

shutter angle

shutter_angle

180

Sets the camera shutter angle from 0-360 degrees.

This is used in combination with the Viewer's playback fps setting to compute exposure values.

gl buffer depth

gl_buffer_depth

float

Sets the OpenGL buffer depth and enables the use of the GPU for the Viewer process and input process:

byte - converts to 8-bit with error diffusion.

half-float - converts to 16-bit (half) float.

float - uses a full 32-bit floating point texture (may be very slow on some cards).

In half and full float modes, the GPU can be used to apply Viewer effects like gamma and the LUT in a Viewer process.

Note:  You can choose a default value for this setting in the Preferences or by using knobDefault() in a startup script.

use GPU for viewer when possible

useGPUForViewer

on

When enabled, Viewer effects (like gain, gamma, and viewer process node) are applied using the GPU when possible.

The ’when possible’ clause is due to the fact that in some cases, like when the GL buffer depth is 8-bit, effects must be computed in the CPU.

use GPU for input when possible

useGPUForInputs

on

When enabled, compute nodes connected to the Viewer input on the GPU when possible, though not all nodes have a GPU implementation.

disabled GPU dithering

disableGPUDitherForViewer

off

When enabled, GPU dithering is allowed in the Viewer (which affects half-float and float modes).

dithering algorithm

GPUDitherAlgoithmFor Viewer

high frequency

Sets the frequency of dithering applied to GPU enabled compositing Viewers, so that you can be sure you're working in a consistent environment:

high frequency - the default setting, applies a high frequency dithering algorithm in screen space, after any viewer rescaling is applied. As you pan and zoom the Viewer, dithered pixels remain the same scale.

low frequency - applies a low frequency dithering algorithm in image space, before any viewer rescaling is applied. As you zoom in the Viewer, dithered pixels get bigger.

no dithering - disables GPU dithering.

Note:  When the Viewer AB mode is changed to wipe or stack, the state of the GPU acceleration controls is stored, GPU acceleration is turned off, and GPU acceleration is disabled.

When the Viewer AB mode is changed back to default, GPU acceleration is re-enabled and the state of the GPU acceleration controls is restored.

view transform

viewerProcess

sRGB

Sets the Viewer Process operation applied to the viewed image before it is displayed on the screen. It is typically used to convert from linear to your monitor's colorspace.

Note:  The control label has been updated, but the knob name currently remains the same. The knob name will also change in a future release.

You can add your own processes to the dropdown using the Python nuke.ViewerProcess.register() function. See Creating Custom Viewer Processes for more information.

input process

input_process_node

VIEWER_INPUT

Sets the name of a node to process through for viewing when the IP button is activated. If the node does not exist, the IP button has no effect.

input_process

disabled

Applies the input process node before displaying the image.

To define the node to use, enter its name in the input process field or, from the Node Graph right-click menu, select Edit > Node > Use as Input Process.

input process order

viewerInputOrder

before viewer process

Sets when the input process node specified is applied:

before viewer process.

after viewer process.

viewer selector mode

viewerSelectorMode

rectangle selection

Sets the selection mode for the current Viewer:

rectangle selection

ellipse selection

lasso selection

viewer transform space

viewerTransformSpace

object

Sets the transform space to use in the Viewer:

object - transforms in this space are relative to the object itself and its orientation. For example, translating on the X axis in object space might shift its position on the Z axis in world space.

screen - transforms in this space are relative to the screen, the flat plane of your monitor, and its orientation. You can only translate on the X and Y axes, the Z axis is disabled.

world - transforms in this space are defined by the XYZ axes of the scene in Nuke's 3D Viewer. The mini axes drawn at the bottom left of the Viewer always show world space no matter what space you're working in.

3D Tab

renderer

renderer

GL

Currently, only one Hydra delegate is available in Nuke, the GL renderer, which handles the USD-based geometry. Classic 3D system geometry is still drawn with Nuke's classic renderer, regardless of which Hydra render delegate you choose.

In future releases, more render delegates will be made available.

Lighting

enableLighting

on

Enable or disable lights, materials, shadows, and progressive rendering in the 3D Viewer, depending on which 3D system you're using.

Materials

enableSceneMaterials

on

Shadows

shadowsEnabled

on

Progressive Rendering

progressive_rendering

on

Display Purposes

display_render

on

Controls whether objects with a Purpose assigned in the new 3D system are visible or not.

Note:  Objects with Purpose set to default are always visible in the scene.

display_proxy

off

display_guides

off

Refine Level

refine_level

0

Sets the level of refinement on subdivided prims in the new 3D system. Higher values produce better visual results, but at the cost of performance.

Note:  The Refine Level only affects the Viewer output, not the final rendered scene.

grid position xyz

grid_origin

0, 0, 0

Sets the position of the grid in the 3D Viewer on the x, y, and z axes.

display

display

unchanged

Adjust the display characteristics of 3D objects. These settings don’t affect the render output of the scene; these are for display purposes only in the 3D Viewer.

off - hides all 3D objects.

wireframe - displays only the outlines of object geometry.

solid - displays all object geometry with a solid color.

solid+lines - displays the geometry as solid color with individual object’s geometry outlines.

textured - displays only the surface texture of objects.

textured+lines - displays the wireframe plus the surface texture.

unchanged - doesn't change object display modes.

Note:  This setting can override individual object settings.

transparency

use_alpha

on

When enabled, objects appear transparent where their alpha is < 1.

headlamp

gl_lighting

off

When enabled, objects are shaded with a spotlight attached to the viewpoint to make their shape visible.

alpha clipping

gl_alpha_clip

1

Sets the alpha value used by the transparency control which determines if an object is opaque or not.

polygon offset

gl_poly_offset

1

Sets the visibility of lines in hidden-line mode.

show

show_points

off

When enabled, all points are displayed in the 3D Viewer.

show_point_num

off

When enabled, all points are numbered in the 3D Viewer.

show_point_info

off

When enabled, all points are labeled with xyz coordinates in the 3D Viewer.

show_point_normals

off

When enabled, all available point normals are displayed in the 3D Viewer.

show_point_uvs

off

When enabled, all available point uvs are displayed in the 3D Viewer.

show_vertex_num

off

When enabled, all vertices are labeled in the 3D Viewer.

show_vertex_normals

off

When enabled, all available vertex normals are displayed in the 3D Viewer.

show_vertex_uvs

off

When enabled, all available vertex uvs are displayed in the 3D Viewer.

show_prim_num

off

When enabled, all primitives are labeled in the 3D Viewer.

show_prim_normals

off

When enabled, all primitive normals are labeled in the 3D Viewer.

show_prim_bbox

off

When enabled, all primitive bounding boxes are labeled in the 3D Viewer.

grid_display

on

When enabled, a grid displays in the 3D Viewer.

default lens

default_lens

1

Sets the default lens (focal length divided by film width) to use in 3D mode when no camera is selected.

near

near

0.1

Sets the limit of the OpenGL near clipping plane. Objects closer to the camera that this value are not rendered the 3D Viewer.

far

far

1000

Sets the limit of the OpenGL far clipping plane. Objects farther away from the camera that this value are not rendered the 3D Viewer.

The far clipping plane can be moved farther away if objects in the scene are farther away. In this case, the near plane is also moved so that the ratio between near and far planes is preserved.

skew order

skew_order

XY

Sets the order in which skew operations are applied.

XY - Skew on the X axis is applied before skew on the Y axis.

YX - Skew on the Y axis is applied before skew on the X axis.

Soft Selection

Soft Select

softSelect

disabled

When enabled, soft selection is applied to any selection made in the Viewer.

When disabled, selections are made in the same way as legacy versions of Nuke.

Falloff Radius

softSelectRadius

1

Controls the radius of the selection falloff added to the initial selection. Increasing the value includes selections from farther away from the initial points or faces.

Falloff Curve

softSelectActiveCurve

S-shaped

Sets the curve used to describe falloff farther away from the initial points or faces.

curves

softSelectCurves

none

Adjusts the preset curve selected in the left-hand panel. You can also add your own curve to control falloff using the + button.

Adding a custom curve adds it to the Falloff Curve dropdown.

MonitorOut Tab

Enable Monitor Out

enable

enabled

When enabled, the Viewer output is sent to a floating window, NDI session, or monitor out device, such as AJA or Blackmagic Design card. The type of output is specified using the Device dropdown.

Device

device

Floating Window

Sets the Viewer output destination:

Floating Window - Nuke's native monitor out uses a floating monitor and does not require additional hardware.

NDI - A network protocol that enables video, and metadata signals to be sent over standard IP networks in real-time. This option allows you to easily share a stream of the Viewer output with anyone else on the network.

Note:  To view the NDI stream, you need the NDI Monitor application installed. See Streaming Viewer Output Over the Internet with NDI® for more information.

Dedicated Monitor Out Card - Nuke supports various AJA and Blackmagic devices that can be selected from the Device dropdown after installation.

Minimize with Application

minimizedWithApplication

enabled

When enabled, minimizing Nuke also minimizes the Floating Window monitor out feed.

When disabled, minimizing Nuke has no effect on the Floating Window.

Note:  This control is only displayed when Device is set to Floating Window.

Input Setup

AB Mode

monitorOutABMode

Active Buffer

Select the view mode using the AB Mode dropdown:

Active Buffer - the monitor always shows the output from the buffer currently in use by the selected Viewer.

Buffer A - the monitor always shows the output from the selected Viewer buffer A.

Buffer B - the monitor always shows the output from the selected Viewer buffer B.

Interactive - the monitor shows the output from the selected Viewer including the A/B player mode currently in use, such as wipe.

Input Process

Use Input Process

monitorOutInoutProcessActive

disabled

Enable Use Input Process to apply an input process node before displaying the image on the external monitor or floating window. This allows you to display different color information in Nuke's Viewer and monitor or floating window.

To define the node to use, enter its name in the Viewer node's input process field or, from the Node Graph right-click menu, select Edit > Node > Use as Input Process.

Output Setup

Display Mode

monitorOutDisplayMode

From Source

Select the resolution output from the monitor card currently in use. The resolutions available depend on the card manufacturer.

Note:  Floating monitor out always uses the resolution of the Viewer in use.

Pixel Format

monitorOutPixelFormat

8 bit

Select the pixel format output from the monitor card currently in use. The formats available depend on the card manufacturer.

Use Viewer Gamma and Gain

monitorOutUseViewerGammaGain

disabled

Enable Use Viewer Gamma and Gain to apply the active Viewer’s filtering, gamma, and gain to the monitor out.

Vertical Flip

monitorOutVerticalFlip

disabled

Enable Vertical Flip to flip the output vertically. This control is handy if you're using a ceiling mounted projector.

Horizontal Flop

monitorOutHorizontalFlop

disabled

Enable Horizontal Flip to flop the output horizontally.

Output Transform

monitorOutOutputTransform

None

Select the color transform to apply to the image. If you’ve specified an OCIO configuration file in the preferences, these custom LUTs are also applicable.

Color Gamut

monitorOutHdrColorGamut

Rec.2020

Sets the color gamut sent as part of HDR metadata signals.

Electro-Optical Transfer Function

monitorOutEOTFHDRMetadata

Perceptual Quantizer

Sets the electro-optical transfer function (EOTF) to apply to HDR displays:

Perceptual Quantizer - the default method for viewing HDR output.

Hybrid Log Gamma - used for HLG compatible devices.

Step-by-Step Guides

Compositing Viewers

Reviewing Your Work with Monitor Out in Nuke (NDI - SDI/HDMI)