Houdini 20.0 Basics

Viewing the scene

On this page

Overview

In Houdini, you can always switch to the camera tool in the viewer by holding Space or Alt. Then you can use the mouse to change the view.

For using a 3D mouse, please see the 3D mouse input page.

(You can turn off Use Alt Key for View Controls in the main preferences.)

Note

If you're used to 2D graphics applications, remember that in Houdini, “zooming” means changing the focal length of the virtual camera lens, not enlarging the view.

Tumbling, tracking, and dollying

Space + LMB

Tumble

Space + RMB or mouse_wheel

Dolly

Space + MMB

Track

Space + ⌃ Ctrl + LMB

Tilt the camera

Space + ⌃ Ctrl + RMB

Zoom the camera lens

⌃ Ctrl + Alt + LMB

Box zoom. Drag the box from left to right to zoom in on the area inside the rectangle. Drag the box from right to left to zoom out (so the current view fits inside the rectangle).

⌃ Ctrl + Alt + RMB

Box crop. Drag the box from left to right to crop to the area inside the rectangle. Drag the box from right to left to reset to an uncropped view. Changing the crop area while looking through a camera that is not tied to the view will ignore that camera’s corresponding parameters until reset to an uncropped view or a new camera is used.

⌃ Ctrl + Alt + MMB

Screen Pan. Pan the screen window of the camera (the camera position does not change) Panning the screen window while looking through a camera that is not tied to the view will ignore that camera’s corresponding parameters until reset to an uncropped view (see box crop above) or a new camera is used.

Space + Z

Center view tumbling on the point under the cursor.

Space + H

Home: center the view to show all objects/geometry.

Space + G

Center the view on all selected objects/geometry.

Tip

Hold ⇧ Shift while tumbling, dollying, tracking, or tilting for more precision.

View pivot

You can choose to tumble, dolly, and zoom based on the view center, or based on the mouse position.

To...Do this

Set the tumble, dolly, and zoom modes

In the View tool (click the View tool in the toolbox to the left of the view, or hold Space), click the icons in the toolbar at the top of the view.

Tumble around the center of the view (or the set pivot). (See below for more information.)

Tumble around the geometry under the mouse pointer. (See below for more information.)

Dolly toward/away from the center of the screen.

Dolly toward/away from the mouse pointer.

Zoom the camera lens on the center of the screen.

Zoom the camera lens on the mouse pointer.

Alternatively, you can right-click the View tool in the toolbox to the left of the view to get a menu of options.

Tumbling

Tumbling can pivot around the center of the scene (effectively), or around the geometry under the mouse pointer.

Technically, the difference between these two modes is:

  • “Keep Pivot” mode doesn’t change the pivot based on the mouse position. Since the default tumble pivot is at the origin, and by default the pivot moves with you when you track the view, this has the effect of tumbling around the center of the view.

  • “Set Pivot” mode (the default) sets the pivot if you start tumbling over geometry. This tumbles around the geometry point the mouse was over. If you click in empty space, tumbling centers around the previous pivot.

    Note that by default the pivot moves with you when you track the view, so even if you tumble around a piece of geometry, if you move the view, the pivot point will move with you. This is often OK since it prevents you from accidentally tumbling around far-off geometry, however you can turn off pivot tracking in the preferences.

2D pan and zoom (screen window)

  • When the view tool is active, you can use icon buttons in the operation toolbar (above the view) to switch between normal 3D camera mode and 2D Pan and Zoom mode.

  • When in 2D Pan and Zoom mode, you can use LMB to pan the view in the 2D plane of the camera lens, and RMB to “zoom” to scale the view up and down.

    ⌃ Ctrl + RMB to box zoom also works.

  • An overview appears in the top-left corner of the viewport. In the overview, a blue rectangle represents the original/default camera view, and a yellow rectangle represents the current 2D view.

    You can also pan the view by dragging the yellow rectangle in the overview.

  • When the view window does not match the camera view, Houdini displays a small indicator in the Camera menu in the top right corner of the viewport.

  • To reset the 2D view to the default camera view, click button in the operation toolbar.

    You can also ⌃ Ctrl-click in the overview to reset the view.

  • If you are looking through a camera and the view is locked to camera (see viewing through cameras below), then when you change the view in 2D Pan and Zoom mode, the changes are written into the camera’s “screen window” parameters.

Note

If you switch back to 3D camera mode while the view is offset or zoomed, Houdini will not automatically reset the view (you can continue to tumble, track, dolly, etc. in the offset view).

To reset the view to the camera, click button in the operation toolbar, or ⌃ Ctrl-click in the overview.

  • When viewing a render delegate’s output in LOPs, you can draw a crop area to restrict rendering to a smaller area of the image by dragging ⇧ Shift + LMB. To reset the crop area to the full frame, click Shift+LMB.

Tips

  • You can hold Space + Z and click in the viewport to set the origin manually. “Set Pivot” mode just automates this to always set the pivot when you start tumbling over geometry.

  • Homing the view to the origin (Space + H) will also reset the view pivot to the origin.

  • Whatever mode you set for , you can switch to the other mode by holding L while you change the view.

    For example, if you have Houdini set to set the dolly toward the view center, you can hold Space + L and drag LMB to tumble around the view center.

Options

  • To make the tumble pivot visible in the view, click the Display Options button to the right of the 3D viewer, click the Guides tab, and turn on View pivot.

  • By default, tracking the view (moving the view up, down, left, or right) moves the tumble pivot as well.

    This is usually what you want, because in “Keep pivot” mode it keeps the pivot at the center of the view, and even in “set pivot” mode it prevents you from moving the view and then accidentally tumbling around a far-off pivot causing confusion.

    However, there may be times when you want to set the pivot on a specific point on the geometry you're working on, and not have it move even as you track around the model.

    To set the preference so tracking does not affect the view pivot, in the main menus choose Edit ▸ Preferences ▸ 3D Viewports and click Maintain viewport pivot when panning.

  • To automatically set the view pivot to the selected geometry when you make a selection, choose Edit ▸ Preferences ▸ 3D Viewports and turn on Automatically set view pivot on selection.

  • To set whether ghosted objects and templated geometry count as “geometry under the mouse pointer” for tumbling, right-click the View tool in the toolbox to the left of the view to get an options menu. (The default is to ignore ghosted and templated geometry).

First person navigation

First-person navigation (sometimes called flythrough mode in other packages) lets you move the camera through the scene using movement keys and “mouse look”, similar to moving through a level in a first-person video game.

To...Do this

Turn on first-person navigation mode

  1. Select the View tool.

  2. In the operation toolbar (above the viewer), turn on First Person Navigation mode, or press M.

    To exit first-person mode, turn off the button in the toolbar, or press M or ⎋ Esc.

Note

Currently, first-person mode only works when you switch to the View as the active tool. Holding Space to temporarily activate the View tool does not work with the first person mode.

Move and rotate the camera in first-person mode

W/A/S/D

Move forward/backward/left/right.

I/J/K/L

Rotate the view up/down/left/right.

Drag LMB

Mouse look.

Q/E

Move down/up.

Drag MMB

Drag left/right to pan, drag up/down to dolly.

Drag RMB

Drag left/right to pan, drag up/down to move vertically.

R/F

Roll counter-clockwise (left)/clockwise (right) around view direction.

You can swap the WASD and IJKL key clusters using “left handed” mode in the tool preferences (see below).

Jump to some geometry

Double-click geometry in the viewer to “jump” the camera directly in front of it.

Change the movement speed

mouse_wheel

Control movement speed.

1/2

Reduce/increase movement speed.

Hold ⇧ Shift

Temporarily increase movement speed.

Hold ⌃ Ctrl

Temporarily decrease movement speed.

You can also set the speed, and change the default, in the tool preferences (see below).

Customize first-person navigation options

  1. Select the View tool.

  2. In the viewer, press P to show the tool preferences.

    You can change the following options:

    • Lock vertical movement (this may be useful when you want to walk around a ground plane without accidentally “taking off”).

    • Invert mouse up/down (when dragging LMB to look around).

    • “Left handed” mode (swaps they key clusters so WASD is rotate and IJKL is move).

    • Movement and turn speeds.

    • Reticle controls.

  3. When you're finished, close the window.

Access overridden view functions

Click RMB in the viewer to access functions whose hotkeys are overridden by first-person mode, such as setting and jumping to quick-marks.

The view and cameras

In Houdini, unlike in Maya, the view is usually independent of any camera object. However, you can lock the view to a camera, and have the view keys move and rotate that camera.

To...Do this

Match the view to a camera or light

Click the camera menu in the viewport (to the right of the viewport options menu) and choose a camera or light to look through.

Normally using the tumble keys after looking through a camera or light will switch the view back to “no cam” – by default the view has no connection to a camera/light. See the Lock camera/light to view button below for how to tie the view to a camera or light.

Note

To prevent cameras from appearing in the viewport menu, add a spare parameter named viewmenu to the camera you want to hide and change the value to 0.

Match a camera or light to the current view

  1. Click the camera menu in the viewport (to the right of the viewport options menu) and choose Save view.

  2. Choose a camera or light from the pop-up menus and click Accept.

Moves and rotates the chosen camera or light to look down the current view.

Use the view keys to position a camera or light

Normally the Houdini viewer is set to “no cam”, meaning it’s not looking through any camera or light. When you choose a camera or light from the camera menu, the viewer switches to look through that camera/light, but if you use the tumble/track/dolly controls to change the view, the viewer switches back to “no cam”. Using the view keys to change the view does not normally move a camera or light.

To use the view keys to move the camera or light you are looking through, you need to lock the view to the camera/light.

  1. Choose a camera or light from the camera menu in the viewport.

  2. In the display toolbar (on the right side of the viewer), click the Lock camera/light to view icon.

    or

    Open the camera menu in the viewport and choose Tie camera (or light) to view.

  3. Use the view keys (see above) to move the camera or light.

Tip

By default, the view is exported to the camera or light when the mouse button is released. This behavior can be overridden by turning on Export view continuously in the viewport camera menu. This option should be used with caution as exporting the view can trigger cooking.

Create a new camera from the current view

Click the camera menu and choose New camera, or Ctrl-click a camera or light icon on the shelf.

See the sections on cameras and lights for more information.

Viewport layout

By default the scene view shows a single perspective view.

You can split the view into sub-views showing different view types, such as orthographic views or UV texture space. For example, you can switch to a quad-view showing top, side, front, and perspective views.

To...Do this

Change the viewport layout

By default the scene view shows a single perspective viewport. Click the viewport layout menu in the top right corner of the scene view pane, and choose a layout.

Change the type of view in a viewport

Click the Viewport options menu in the top-right corner of the viewport, and open the Set view submenu.

Resize the viewports within a layout

  • Move the mouse over the divider between two viewports and drag.

    or

  • Move the mouse over the intersection between multiple viewports and drag to resize all adjacent viewports at the same time.

  • To restore the default sizes, click the viewport layout menu in the top right corner of the scene view pane, then click Restore Default Viewport Layout (near the bottom).

Set your layout sizes as the default

  • Each layout remembers is own split sizes.

  • The split sizes are saved in the scene file, so each file can have different layout sizing.

To set your split sizes as the default for the current layout, do the following:

  1. In the display toolbar to the right of the view, click Display Options to open the Display Options window.

  2. In the Display Options window, click Save as Default.

    Note that this will save all current display options as the new default. If you only want to save viewport splits, create a new file, change the viewport splits, and click Save as Default with that otherwise “clean” file.

Temporarily maximize one viewport

Move the mouse over the viewport and press Space + B. Press Space + B over the single viewport again to switch back to the multi-viewport layout.

Make orthographic viewports pan and zoom together

Open the viewport layout menu and turn on Link ortho views.

Changing how Houdini displays the scene

To change the shading mode, click the shading mode icon in the viewer’s toolbar.

Wireframe bounding box

Only draws a wireframe bounding box to represent geometry.

Shaded bounding box

Only draws a shaded bounding box to represent geometry.

Wireframe

Draws curves, surface isoparms, and polygon edges.

Wireframe Ghost

Like Wireframe, but ghosts (dims) lines obscured by surfaces.

Hidden line invisible

Hidden line ghost

Like Hidden Line Invisible, but ghosts (dims) lines obscured by surfaces.

MatCap shaded

Uses a MatCap texture to define the shading of the surface, ignoring all other material assignments and scene lighting.

Flat wire shaded

Like MatCap shaded, but also draws the wireframe over the shaded surfaces.

Flat shaded

Shades polygons but does not blend between them, making them appear faceted.

Flat wire shaded

Like flat shaded, but also draws the wireframe over the shaded surfaces.

Smooth shaded

Blends between shaded polygons making them appear smoother.

Smooth wire shaded

Like smooth shaded, but also draws the wireframe over the shaded surfaces.
To...Do this

Switch between wireframe and shaded mode

Press W in the viewer.

or

Open the viewport options menu and choose Shading ▸ Toggle wireframe/shaded.

Open the full display options window

Click the display options button to the right of the viewer, or press D over the viewer.

Hide the grid

Click the Display Reference Plane/Ortho Grid button in the display options toolbar to the right of the view.

Put an image in the background of a viewport

  1. Click the display options button to the right of the viewer, or press D over the viewer.

  2. Click the Background tab.

  3. Turn on Display Background Image.

  4. Click the sub-tab corresponding to the viewport type you want to have a background image (for example, Pesp(ective), Top, UV, etc.).

  5. Click the file chooser button to the right of the Disk file field to choose an image file.

(You can change “Disk file” to “COP image” to load the image from a compositing node instead.)

Display toolbar

The toolbar along the right side of the viewport has controls for what Houdini draws in the 3D viewer and how it draws the scene.

Show reference plane

Draws a grid on the reference plane, that is the plane centered at the origin, perpendicular to the up direction (by default, the XZ plane).

Right-click this button for a menu of options related to the reference plane grid.

Show construction plane

Displays the construction plane, which you can move and rotate to make it easier to draw, position, and snap along a plane.

Right-click this button for a menu of construction plane options, such as showing the construction plane’s handle, allowing you to move and rotate it.

Lock camera/light to view

If you are looking through a camera (or light) and turn this option on, moving the view using the tumble/track/dolly keys in the viewer will move and rotate the locked camera/light as well.

No lighting

Don’t simulate lighting in the viewer. All surfaces are lit using a constant ambient light, with no shading.

Headlight

Shade the scene as if it was lit by an ambient light and a headlight attached to the view origin. Does not simulate the effect of actual lights in the scene.

Right-click this button for a menu of lighting components to use.

Normal lighting

Shade the scene by approximating contributions from lights in the scene.

Right-click this button for a menu of lighting components to use.

High-quality lighting

Shade the scene with more accurate approximation of the contributions from lights in the scene.

Right-click this button for a menu of lighting components and quality options, such as simulating reflections.

High-quality lighting with shadows

Shade the scene with more accurate light approximation and simulated shadows.

Right-click this button for a menu of lighting components and quality options, such as shadow quality.

Display materials

Turn this on to show OpenGL approximations of materials in the viewer.

Right-click this button for a menu of display and quality options.

Object type visibility

Click this button to show a menu of different object types to show/hide in the viewer.

Object type visibility during playback

This is a filter on what object types (currently visible in the object type visibility settings above) to show when animation is playing.

Right-click this button to turn certain object types on or off.

Click this button to turn the filter on or off. When the button is on, only object types turned on in the filter menu will appear during playback.

(When the filter is on it also affects flipbook animations, but not a single-frame flipbook.)

Points

Draw small markers on points.

Point normals

Draw lines representing point normals.

Point trails

Draw lines visualizing each point’s velocity (v) attribute. You can add velocity attributes to points using the Trail geometry node.

Point numbers

Next to each point draw its number.

Primitive normals

Draw lines representing the face polygonal normals.

Primitive numbers

Next to each primitive (for example, polygonal face) draw its number.

Hulls

Draw hull wireframes for types such as NURBS and Bézier.

Vertex markers

Draw markers indicating vertices.

Particle origins

Draw small axes on particles to show their orientation.

Show group list

Shows or hides the group list box in the viewer.

Display object names

Draws the names of objects next to the objects in the viewer.

Display background

If you set up viewport background image(s) in the display options, use this button to show or hide the background images.

Visualization

Right click this icon to show the visualizer menu.

Click this button to globally show or hide all active visualizers.

Viewport messages

Press and hold on this button to show messages/statistics generated for the current view.

Apply to all split views

When the viewer is split into sub-viewports, click this button to switch between the toolbar affecting all viewports, or just the current viewport (usually the last viewport you clicked in).

Display options

Show the display options window.

Resetting the view

Homing means to reset the view, either to a default view looking at the origin. You can also home to show all objects in the scene, or to show the selected objects. This is similar to the “zoom to fit” functionality in 2D illustration programs, PDF and image viewers, and so on.

Homing and framing controls are located in the viewport options menu (the left menu in the top right corner of viewports). This menu contains commands for homing the view, and lets you customize the default home view. For most homing functions, you’ll want to use the hotkeys.

To

Viewport menu

Hotkey

Zoom to fit all objects

Home ▸ Home All

Space + A

Zoom to fit the selected objects

Home ▸ Home Selected

Space + G

Zoom to fit the grid

Home ▸ Home Grid

Space + H
To...Do this

Change the home view to a look along an axis

Open the viewport options menu, click Home, then choose a view direction (along the X-axis, Y-axis, or Z-axis).

Change the home view to look along a custom direction

  1. Use the tumble keys (see above) to get the view you want as a custom home.

  2. Open the viewport menu, click Home, then choose Customize Home.

  3. Open the viewport menu and click Home again, then from the list of home options choose Custom.

  4. Now when you use the homing hotkeys, you should return to this view.

Showing other objects at the geometry level

When you're editing inside an object, you can choose how/whether Houdini shows other objects in the scene using the Show all/current/ghosted menu.

Show ghosted

Other objects/levels appear “ghosted” (semi-transparent). This is the default.

Show others

Show other objects and levels normally.

Hide others

Only show the geometry at the level you're working and hide others.

Setting display options for various levels/states

You can set up different feature display and shading options for all geometry, selected geometry, geometry near the mouse pointer, and other states. For example, you can only show point numbers on points near the mouse pointer, or only on selected geometry, to avoid cluttering the display.

  1. Click the display options button to the right of the viewer, or press D over the viewer.

  2. Click the Markers tab.

  3. Choose the state you want to change from the Set display options for menu.

    This menu controls what category of geometry the options below apply to.

    Scene Geometry

    Display options for unselected objects at the object level look like.

    Selected Scene Geometry

    Display options for selected objects at the object level. By default this is the same as “Scene geometry”.

    Ghost Scene Geometry

    When you are at the geometry level (inside a Geometry object), you can optionally show other objects “ghosted” (semi-transparent). This shows display options for these ghosted objects.

    Display Model Geometry

    At the geometry level (inside a Geometry object), display options for the output of the node with the display flag.

    Current Model Geometry

    Display options for the selected geometry node’s output. At the geometry level, when you select a node that doesn’t have the display flag, the view shows the output of the selected node (by default, as wireframe) along with the output of the network. This lets you edit the node and see the effects in the view.

    Template Model Geometry

    Display options for “templated” geometry. You can set the template flag on a geometry node to keep the node’s output visible at the geometry level alongside the display geometry.

    Note

    The Use menu next to this menu might be set to use the settings from another state. You can set Use to “Unique settings” to give the chosen state its own settings.

  4. Click the checkbox next to the features you want to be visible in this state.

    Use the visibility icon menu to the right of each option to control when the given feature is visible (always, selected, near pointer, under pointer).

  5. In the rightmost column, choose the shading style and drawing options for geometry in the chosen state. For example, Ghosted draws the geometry semi-transparent, and Faded dims its colors to make it slightly less visible.

Color correcting the view

To show the color correction toolbar, click the view dropdown menu (beside the camera menu) in the top right corner of the viewport and turn on Correction Toolbar. The toolbar can also be shown using the toggle in the RMB menu on the Display Options button, at the bottom of the right viewport toolbar.

See OpenColorIO support for more information.

Material display

Materials can be assigned to geometry by dragging and dropping a material from the Material Palette or Network Editor onto object geometry. Materials can also be assigned with a Material SOP or Material Stylesheet.

Material display can be disabled by clicking by Display Materials toggle on the right viewport toolbar. Finer control over material assignments and options, such as texture display, particle display, and transparency, can be found in its RMB menu.

Basics

Getting started

Next steps

Customization

Guru-level