Houdini 20.0 Reference Panes

Render gallery

The render gallery lets you “snapshot” the current view, so you can compare images and revert to when a snapshot was taken.

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Overview

The render gallery makes it easy to explore different settings, materials, lighting setups, and so on, compare the different looks. When you decide on the right look, you can revert the LOP network to match how it was set up when a snapshot was taken.

The render gallery is available as a sub-pane of the Solaris Viewer, or as a separate Render Gallery pane type.

  • The sub-pane is a strip of snapshot images below the Solaris viewer, with controls for taking and managing snapshots. You can double-click a snapshot to open it in a full Render Gallery pane.

  • The full pane includes both the snapshot strip and an image viewer, allowing you to view or compare snapshot images.

Each render gallery is associated with a LOP network (for example /stage). See render gallery storage below for more information.

  • The Show/Hide Render Stats button in the icon bar opens a section with detailed statistics about the current snapshot. You can see information like memory usage, time to first pixel, pixel samples, time, spent on shadows or lighting, objects counts, and many more.

Note

The render gallery is only available in the Solaris viewer for LOP networks. It is not available in the OBJ/SOP scene viewer, or the Mantra IPR view.

Showing the render gallery

To...Do this

Show/hide the render gallery in the Solaris viewer

Click the Render Gallery button near the bottom of the Display toolbar on the right side of the Solaris viewer.

Add a Render Gallery pane tab to the pane layout

In the pane where you want to add the tab, click the plus button at the end of the tabs, then choose New pane type ▸ Solaris ▸ Render gallery.

Open a floating Render Gallery window

  1. In the main menus, choose Windows ▸ New floating panel.

  2. In the new window, right click the pane tab at the top and choose Solaris ▸ Render gallery.

Working with snapshots

To...Do this

Take a snapshot of the current view

Click Snap in the toolbar. This captures the current view/network as a new snapshot in the snapshot strip.

Start a background render snapshot

Click Background in the toolbar. This starts a background render of the current view as a new “live” snapshot in the snapshot strip.

  • The snapshot thumbnail contains to update as the render progresses in the background.

  • “Live” rendering snapshots have a Render icon in the top left corner.

  • If open a live rendering snapshot in a render gallery viewer pane (see “view a snapshot” below), you can click to focus rendering.

  • To stop a background render, right-click the live snapshot and choose Stop Rendering. The snapshot will use the last image output of the render as the snapshot.

If necessary, an expert user can write a background render plugin that implements some other type of background render, for example using a different farm management tool, or using a proprietary studio render pipeline.

Start a background render on an HQueue farm

  1. Right-click the Background button in the toolbar. Choose HQueue.

  2. In the dialog window, enter the information for how to render the snapshot, the address of the HQueue farm controller, and a name for this job. Click OK.

Select a snapshot

  • LMB click the thumbnail in the snapshot strip. Selected snapshots have a yellow border around the thumbnail.

  • ⌃ Ctrl + LMB to toggle selection.

  • ⇧ Shift + LMB to add to the selection.

  • Drag a selection box to select multiple snapshots at once.

View a snapshot

  • Click a thumbnail. If a render gallery pane If a render gallery pane is available in the current pane layout (and is viewing the same gallery database), it will display the same image.

    Single-click viewing is disabled if you are diffing two images in the render gallery view.

  • If a viewer is not currently open, you can double-click a thumbnail to show the full image in a floating render gallery pane.

    This replaces any previous image or diff in the viewer.

  • See viewing snapshots below for how to use the render gallery’s viewer.

Delete a snapshot

  • Select the thumbnail in the snapshot strip and press ⌦ Del.

    or

  • Right-click the thumbnail in the snapshot strip and choose Delete.

Restore the LOP network to the state saved with a snapshot

Right click the snapshot and choose Revert network to this snapshot.

Tip

You can choose Edit ▸ Undo in the main menus to undo reverting to a snapshot.

Viewing and comparing snapshots

The render gallery pane interface is similar to MPlay and the Compositing View. See the toolbar reference below for an explanation of all the controls in the render gallery view.

To...Do this

View a snapshot

  • Click a thumbnail. If a render gallery pane If a render gallery pane is available in the current pane layout (and is viewing the same gallery database), it will display the same image.

    Single-click viewing is disabled if you are diffing two images in the render gallery view.

  • If a viewer is not currently open, you can double-click a thumbnail to show the full image in a floating render gallery pane.

    This replaces any previous image or diff in the viewer.

  • See viewing snapshots below for how to use the render gallery’s viewer.

Navigate around the image

  • Hold Space, then:

    • Drag MMB to pan.

    • Drag RMB to zoom.

    • Drag ⌃ Ctrl + RMB to box zoom.

    • Use mouse_wheel to zoom.

  • Turn on the Show/Hide Preview button in the viewer toolbar to show a thumbnail of the entire image in the corner, with a rectangle representing the currently visible part. You can drag the rectangle to pan across the thumbnail.

  • You can also use the Zoom in, Zoom out, Home, and Fit to Window buttons in the viewer toolbar to set the zoom level.

Compare two images in the render gallery view

  1. Set an image as “A” (the first image to compare).

    • Select a thumbnail and click the A button on the strip toolbar.

      or

    • Right-click a thumbnail and choose Set as A.

  2. Set an image as “B” (the second image to compare).

    • Select a thumbnail and click the B button on the strip toolbar.

      or

    • Right-click a thumbnail and choose Set as B.

Tip

You can also select two images and click A or B in the toolbar to set them as A and B in one step.

See the toolbar reference below for the different comparison types.

Show/hide image comparison

  • Marking “A” and “B” images will automatically turn on diffing.

  • If you unmark either “A” or “B” (by clicking the toolbar button again or right-clicking the thumbnail and choose Stop comparing) the render gallery will stop diffing.

  • In the render gallery view, you can click the Show/Hide Diff Bar button on the top toolbar to enable or disable comparison. When this is off, any A/B markers are kept, and shown again if you turn diffing on again.

  • In the diff toolbar, one of the comparison styles is “no diff”. You can use this to temporarily show only the “A” image.

Organizing and searching snapshots

Each snapshot includes various pieces of metadata, some of which you can edit and/or filter:

Image

A snapshot captures the contents of the Solaris viewer as an EXR image. A thumbnail of the image is displayed in the snapshot strip. You can view the full image in a render gallery view.

Label

Each snapshot has an automatic label when it is created, which you can edit to be more descriptive (see below). The label is displayed below the snapshot in the snapshot strip. You can filter snapshots by text in their labels.

Creation time

You can filter the visible snapshots by their creation times.

LOP network

Each snapshot stores the LOP network as it was when the snapshot was taken, so you can choose to revert to it later.

Star

You can “star” a snapshot to make it easy to find later.

Color

You can optionally assign a color to each snapshot. This is an easy way to categorize snapshots quickly. The snapshot strip displays a snapshot’s color as a colored line above the thumbnail.

Tags

You can associate an arbitrary list of tags (single words) with each snapshot in the metadata editor (see below). You can then filter snapshots based on tags. (Starred status is actually stored using the star tag.)
To...Do this

Edit a snapshot’s label

  • Click the label to make it editable, and start typing.

    or

  • Right-click the thumbnail and choose Rename.

    or

  • Edit the snapshot’s label and tags in the metadata editor window (see below).

Star a snapshot

  • Click the star outline in the top right corner of the thumbnail in the snapshot strip.

    or

  • Right-click the thumbnail and choose Star.

  • To un-star a snapshot, click the star icon again, or right-click the thumbnail and choose Unstar.

Assign a color

Select one or more snapshots, then right-click the selection and choose a color from the context menu.

Edit tags and metadata

  • Select the snapshot and click the Edit Metadata button in the snapshot strip toolbar.

    or

  • Right click the snapshot and choose Edit Metadata.

You can edit the snapshot’s label and tags in the metadata editor window.

  • You can type the list of space-separated tags (words) for this snapshot in the text box above the tag list.

  • You can add/remove existing tags using the checkboxes next to the tags in the tag list.

Show only starred snapshots

Turn on the Show Only Starred button on the snapshot strip toolbar.

Show/hide the filter sidebar

Click the Show/Hide More Filters button after the search field in the snapshot strip toolbar.

This opens a sidebar showing different filters.

  • Select a filter item to show snapshots matching that filter.

  • Click a selected filter item again to deselect it.

  • Use the radio buttons above the filter list to choose whether to show snapshots that match any of the selected filters, or all of the selected filters.

Filter by color

  1. Show the filter sidebar (see above).

  2. Select the color(s) to show in the sidebar list.

Filter by tags

  1. Show the filter sidebar (see above).

  2. Select the tag(s) to show in the sidebar list.

Filter by text

Type what to search for in the filter textbox in the snapshot strip toolbar. This matches label text and also tags.

Filter by recently created

  1. Show the filter sidebar (see above).

  2. Select one of the date-based filters, such as “created today” or “created in last 7 days”.

Auto snapshots

When Auto snapshots are on, the render gallery automatically creates a new snapshot when the view re-renders (for example, when you change a parameter). A timer controls how often the gallery should create auto snapshots.

  • Auto snapshots (except the most recent snapshot) appear “collapsed” in the snapshot strip to save space. You can select or hover over an auto snapshot to see the full thumbnail in the strip.

  • Auto snapshots are tagged auto.

To...Do this

Set up auto-snapshots

  1. Click the Option window button in the snapshot strip toolbar.

  2. Set the value for Limit to one snapshot every N seconds.

    For example, if you set this to 10, no matter how many changes you make in a 10 second period, the gallery will only create one automatic snapshot.

Turn auto-snapshots on/off

  • Click the Auto button on the snapshot strip toolbar.

    or

  • Click the Option window button in the snapshot strip toolbar, turn on Auto save.

Set how long to wait to take a snapshot after a change

Currently, the gallery takes an image of the exact contents of the viewer at the moment the snapshot is triggered. When the view is rendered, you probably want to add a delay between the time of a parameter change and the snapshot, to allow the renderer to refine the image. Otherwise the snapshot will show the initial blocky approximation.

  1. Click the Option window button in the snapshot strip toolbar.

  2. Set the Wait N seconds after a change option to how long you want the render gallery to wait for the renderer before taking the snapshot.

Note

Future versions of Houdini should allow “live” snapshots that continue to update as the renderer works, eliminating the need for this delay.

Show/hide all auto snapshots

Click the Show Non-Auto Snaps button in the snapshot strip toolbar.

Toolbars

Main viewer toolbar

View Image

View the render as an image.

View Timeline

This option is disabled in the Render Gallery view.

View Histogram

View the render is a histogram. You cannot use diff mode with histograms.

Image plane menu

Which plane/AOV in the rendered image to display. For example, C (color), A alpha, or a custom plane such as distance.

you can press ⇧ Shift + [ and ⇧ Shift + ] to cycle through the planes in the image.

Zoom In

Increases the magnification.

Zoom Out

Decreases the magnification.

Home

Resets to the default view (centered, 100% magnification).

Fit to Window

Pan and zoom so the image fills the available view space.

Info Window

Press and hold on this button to display a window containing summary data about the rendered image.

Inspect

When this is on, as you move the mouse over the image, a floating window shows data about the pixel under the mouse pointer.

Show/Hide Labels

Draw text over the image showing image file name(s) and metadata such as pixel width/height.

Show/Hide Render Stats

Get detailed information on a snapshot’s render statistics, such as memory usage, ray types, light types, time to first pixel, and many more.

Show/Hide Preview

Shows a thumbnail of the entire image in the corner, with a rectangle representing the currently visible part. You can drag the rectangle to pan across the thumbnail.

Show/Hide Diff Bar

Enables diffing and shows the controls on the diff toolbar (see below).

Show/Hide Color Correction Bar

Shows an extra toolbar with controls for color correcting the displayed images.

Display Options

Shows a window with options for how to display the image, such as the background behind the image.

Diff toolbar

No diff

Only display the “A” image. This may be useful to switch back and forth between the original image and a comparison.

Split Horizontal

Display a split view with A on the left and B on the right. Click in the image or use the slider at the end of the toolbar to move the split point.

Split Vertical

Display a split view with A on top and B on the bottom. Click in the image or use the slider at the end of the toolbar to move the split point.

Compare

Displays the absolute difference between the pixel component values of the two images. This can help highlight subtle differences between two very similar images.

Subtract

Subtracts the pixel component values of the second image from the values of the first image.

Blend

Fades the two images together. The slider controls the percentage of the second image blended with the first.

Highlight Differences

Highlights any pixels in the first image that differ from the second image by more than a threshold set with the slider.

The threshold is measured in normalized color space (1 unit is equal to the range from black to white).

Snapshot strip toolbar

Edit Metadata

Opens a window that lets you edit the label, tags, and other metadata for the selected snapshot.

A

Set the selected snapshot as the first image to compare.

B

Set the selected snapshot as the second image to compare.

Auto

Enable auto-snapshots.

Options

Open a window with options for how the render gallery works.

Source file path

Displays where on disk the current gallery database is stored.

Show Only Starred

Filter the snapshots so only starred snapshots are visible.

Show Only Non-Auto

Filter the snapshots so auto snapshots are hidden.

Search box

Type to filter by label text and/or tags.

Show/Hide More Filters

Opens a sidebar in the strip area with additional options for filtering.

Color correction toolbar

The Correction toolbar contains image component and color controls.

These five buttons control which color plane(s) to show. The first icon shows all the planes (Red, Green, Blue, Alpha/Component 4). The next four turn the individual planes on or off.

The Alpha/Component 4 button will show the fourth component plane if one exists, otherwise it shows the alpha channel.

The default hotkeys for these buttons are ~, 1, 2, 3, and 4.

/ menu button

Switches between Brightness/Contrast controls and Black/White Points.

Press R to reset all color correction controls to their default values.

Click the brightness button to reset the brightness to 1.

Enter a value in the number field for the brightness, or click MMB in the field to show a slider.

The field turns yellow when brightness is not 1.

Click the contrast button to reset the contrast to 1.

Enter a value in the number field for the contrast, or click MMB in the field to show a slider.

The field turns yellow when contrast is not 1.

This value is added to all pixels, effectively shifting the brightness of the entire image up or down. This can be useful for looking through intensity “slices” of the image.

The black point of the image, normally 0. This is applied after any image-specific white and black points, so 0 is always black and 1 is always white, regardless of the image data format.

The white point of the image, normally 1. This is applied after any image-specific white and black points, so 0 is always black and 1 is always white, regardless of the image data format.

Click the gamma button to reset the contrast to the default set in the display options window .

Enter a value in the number field for the gamma, or click MMB in the field to show a slider.

The field turns yellow when gamma is not at the default gamma setting.

Adjusts the black and white points to fit the minimum and maximum pixel values of the current image.

Snapshot storage

  • The LOP network node (for example, /stage) has a Render gallery source parameter that controls where Houdini creates and saves the render gallery database.

    The default is:

    $HIP/galleries/$HIPNAME.$OS/rendergallery.db

    …where $HIP is the directory containing the current scene file, $HIPNAME is the name of the current scene file, and $OS is the name of the current node (that is, the name of the LOP network).

    If you edit this path, you should still include the scene file name and node name in the path, to allow multiple scene files in the same directory, and multiple LOP networks in a scene file.

  • The gallery saves the captured EXR images files in the same directory as the rendergallery.db file.

  • The gallery displays the path of the database file in the snapshot strip toolbar.

  • If the current Houdini scene has not been saved to disk yet, it maintains the render gallery data in memory until the scene is saved.

  • Houdini does not create the database file and any intermediate directories are not until you take a snapshot.

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