Manipulating Models

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

The Transform Control plugin is a combination of keybindings and transform control options: selection, translation, rotation and custom snap values. This chart of Ignition’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 with the center/origin of other entities.

Prerequisites

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

ign gazebo shapes.sdf

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

Transform Control

The shapes.sdf file contains the Transform Control plugin, which is why the plugin is already at the bottom of the screen when you start. If you wanted to use the plugin in a world where it isn’t already included, you would open the plugin drop-down menu and select it from the list:

Select Mode

Selection is the default mode. You can click to select entities in the scene. A selected entity will be highlighted 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 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 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 furthest-right magnet icon in 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

The Component Inspector plugin is included in shapes.sdf. 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

The View Angle plugin does not come pre-loaded with shapes.sdf, so you will have to select it from the plugins button on the toolbar.

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

Like the View Angle plugin, the Align Tool is also not pre-loaded and will also have to be selected from the plugins button on the toolbar.

The Align Tool aligns a model up with the center/origin of another model, or with something besides a model, like a link for example. It can’t, however, align a link or anything other than the top-level model up with something else.

With Relative to First selected, select two models using Ctrl + click to see the second model align to the first along either it’s 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.

You can align more than two models, just select the others with Ctrl + click.

Next Up

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