Manipulating Models

This tutorial will walk you through using various plugins to assist model and scene manipulation in the Gazebo GUI.

The Transform Control plugin is a combination of keybindings and transform control options: selection, translation, rotation and snapping. This chart of Gazebo’s keyboard shortcuts may be helpful for this tutorial.

The View Angle plugin allows you to quickly and easily adjust the direction from which your scene faces an entity in the simulation.

The Component Inspector plugin displays a variety of object attributes.

The Align Tool aligns entities along or about a specific entity’s bounding box.

Prerequisites

Start by getting Gazebo up and running with a sample world:

gz sim shapes.sdf

The previous tutorial, Understanding the GUI, explains the basics of navigating the Gazebo GUI.

Transform Control

The top left toolbar contains controls for transforming. Alternatively, the Transform Control plugin can be selected from the plugin drop-down menu. The plugin will then appear at the bottom of the right panel.

Select Mode

Selection is the default mode. You can click to select entities in the scene. A selected entity will be highlighted in the Entity Tree to indicate its selection. You can select multiple entities by holding Ctrl and clicking.

Entities can’t be manipulated in select mode.

You can always return to selection mode from any other mode by pressing Esc.

Translate Mode

Enter into translate mode by clicking the second icon from the left in the top left toolbar, the Transform Control plugin, or by hitting the keyboard shortcut: T.

Translate mode allows you to translate entities along the x, y and z axes.

Click on any entity while in translate mode to see the arrows representing the axes you can move along. The red arrow represents the x-axis, green the y-axis, and blue the z-axis. Click and hold on any of the arrows while moving your mouse to move the entity in that direction.

Additionally, holding down any one of the X, Y or Z keys, or a combination of them, while clicking and dragging will constrain the model’s movement along those axes, regardless of the direction you move your mouse or the axis arrow you select.

Rotate Mode

Enter into rotate mode by clicking the third icon from the left in the top left toolbar, the Transform Control plugin, or by hitting the keyboard shortcut: R.

Rotate mode allows you to rotate entities around the roll, pitch and yaw axes of rotation.

Click on any entity while in rotate mode to see the circles representing the axes you can rotate along. The red circle represents roll, green is pitch, and blue is yaw. Click and hold on any of the circles while moving your mouse to rotate the entity around that axis.

Align to World frame

An entity’s local axes can become unaligned from the world frame after rotation. If you would like to translate along the world frame axis, simply hold Shift.

This isn’t a permanent realignment; you can move the entity while holding Shift, but once you let go it will return to it’s local translational frame.

The same can be done for an entity’s local rotational frame.

Enter Custom Snap Values

When translating or rotating, you can “snap” an entity’s movement to preset increments by holding Ctrl and then clicking and dragging. By default, the snap value is 1 meter for translation and 45° for rotation.

Translational snaps will snap relative to the world frame, whereas rotational snaps will snap relative to the object’s current orientation.

You can customize snap values by clicking on the snap icon in the top left toolbar or the Transform Control plugin.

Try holding Shift and Ctrl simultaneously to snap a model along the world frame is if isn’t already aligned.

Component Inspector

With this plugin, you can select an entity to display some of its attributes, including its pose, whether or not wind is acting on it, whether or not it’s static, and more. The plugin also displays the gravitational and magnetic fields of your world.

Expanding the Pose attribute will show the coordinate values for a selected object. The values will update as the object is moved around (translated or rotated) while the simulation is running.

You can also pause the plugin so an object’s pose values don’t update in the inspector while the simulation is playing.

Additionally, the Component Inspector can be locked on one object so you can open another Component Inspector to simultaneously observe another object.

View Angle

Select the View Angle from the plugins drop-down menu.

You can choose which angle you want to view the scene from, relative to a selected entity or the world frame if no entity is selected. The home button will return you to the original view pose from when the scene was loaded.

You can also select multiple entities to face simultaneously from each view angle.

Align Tool

Select the Align Tool from the plugins drop-down menu.

The Align Tool aligns a model along or about the bounding box of another model, or any other entity that has a bounding box, like a link for example. It can’t, however, align a child link or anything other than the top-level model.

With Relative to First selected, select two models using Ctrl + click (be sure you are in select mode) and then hover over any of the Align Tool buttons to see a preview of the second model aligning to the first along its x, y or z axis. Hovering over the buttons for each axis will show a preview of where the model would end up if aligned along that axis while clicking will confirm that specific alignment.

The Reverse button will enable alignment about the outer boundary of a model’s bounding box. This feature is helpful for placing objects exactly next to each other. Notice the difference in alignment when the Reverse button is pressed in the gif below.

You can align more than two models as well, simply select more models with Ctrl + click. You can select First or Last in the Relative to: drop down menu to choose which entity to align to.

Next Up

So far you’ve interacted with basic shape models to learn about Gazebo’s GUI. It’s also possible to insert more detailed models from Gazebo Fuel into the GUI. Check out the Model Insertion from Fuel tutorial to learn how.