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

enabled

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

disabled

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

disabled

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

prevent auto zoom

zoom_lock

disabled

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

disabled

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

enable full frame processing

full_frame_processing

disabled

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

disabled

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

enabled

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

enabled

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

disabled

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.

enable monitor output

MonitorOutEnable

disabled

When enabled, the Viewer is output to the connected monitor device.

Note:  You cannot enable this control if no monitor output device is specified.

use video legal range

MonitorOutLegalRange

disabled

When enabled, transform the monitor output to the legal video range.

monitor output device

MonitorOutDevice

None

Sets the monitor output device to receive the Viewer output:

None

Digital Cinema Desktop

Firewire

monitor output mode

MonitorOutMode

-

Sets the display mode for the specified monitor output device:

none - no selections are available.

D - select a Digital output device from the dropdown.

A - select a Firewire output device from the dropdown.

monitor output pixel format

MinorOutPixelFormat

-

Set the pixel format output for the specified monitor output device, dependent on the card's manufacturer.

viewer selector mode

viewerSelectorMode

rectangle selection

Sets the selection mode for the current Viewer:

rectangle selection

ellipse selection

lasso selection

3D Tab

renderer

renderer

Hydra (Storm)

Sets which 3D Viewer type to use:

Hydra (Storm) - a 3D Viewer consistent with other applications in your pipeline, such as Katana, Solaris, or USDView, as well as providing output that much more closely represents the output from ScanlineRender nodes.

Nuke - the legacy 3D Viewer from Nuke 12.2 and earlier. This option doesn't render lights, materials, and shadows as consistently as the Hydra (Storm) Viewer.

Note:  The Hydra (Storm) Viewer is currently only available on Windows and Linux OS.

Lighting

enableLighting

enabled

When renderer is set to Hydra (Storm), enable or disable lights, materials, and shadows in the 3D Viewer.

Materials

enableSceneMaterials

enabled

Shadows

shadowsEnabled

disabled

OIT Number of Samples

rd_oitNumSamples

32

Controls the render quality when you have multiple overlapping semi-transparent objects in the 3D Viewer. Increasing the number of samples improves the rendered output, but uses more OS resources and can affect performance.

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

enabled

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

headlamp

gl_lighting

disabled

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

disabled

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

show_point_num

disabled

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

show_point_info

disabled

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

show_point_normals

disabled

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

show_point_uvs

disabled

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

show_vertex_num

disabled

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

show_vertex_normals

disabled

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

show_vertex_uvs

disabled

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

show_prim_num

disabled

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

show_prim_normals

disabled

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

show_prim_bbox

disabled

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

grid_display

enabled

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.

Step-by-Step Guides

Compositing Viewers