Tutorial Part 6

Tutorial contents:

Adding and Configuring Content

Having added some markers to track, you can now add some content to those markers.

In addition to standard 3D models, BuildAR Pro supports images, movies, text, primitive objects and sounds. These can be added either by themselves or in whatever combination you choose.

To add new content to a marker, right-click on the marker in the scene tree. A popup menu will appear listing the available content types. Select the type you wish to add and a new item representing the content will appear as a child of the marker.

Each content type has some parameters which you can configure through the user interface. A configuration panel for the currently selected content will show in the lower left corner of the interface. Regardless of which content type you add, there are some common rendering options that apply for every content type.

  • Render Order: This value determines the order in which objects are drawn. Sometimes you want to make certain objects be drawn later so that transparency effects look correct. Objects with a higher value are drawn later.
  • Wireframe: This draws the object in wireframe mode (lines). Uncheck for normal rendering (filled polygons)
  • Phantom Object: Check this option to draw only the depth information for the object (no colour). This is used to correctly occlude objects.
  • Enable Lighting: Check this option to render objects with lighting/shading. Uncheck for objects that should be unlit, possibly text or movies.

Content Types

3D Models

Like the original version, BuildAR Pro allows you to place your own 3D models on tracked markers. The same file formats as always are supported, as well as some new ones. Popular formats supported in BuildAR Pro include:

  • 3D Studio Mesh (.3ds)
  • Wavefront Object (.obj, .mtl)
  • Lightwave (.lwo)
  • OpenSceneGraph (.ive, .osg)
  • Autodesk FBX (.fbx)
  • For a complete list, consult the help documentation in the software.

Many 3D models can be downloaded from the internet and loaded directly into BuildAR Pro. TurboSquid, for example, is a large 3D model repository where you can find plenty of free and paid-for 3D content.

Alternatively you can create your own 3D models in any one of the many available 3D modeling packages. Some popular choices include:

IVE and OSG are the native formats of OpenSceneGraph, the graphics library used by BuildAR for rendering. You may not find many files in these formats online, however many other formats can be converted to OpenSceneGraph format using the osgExp plugin for 3D Studio Max.

FBX support is new in BuildAR Pro and provides support for skeletal animation.

To set the current model file, you can use the “Select” button on the panel. Alternatively, you can double-click on the model in the scene tree.

The panel also includes a check box for resetting animations. If this is checked, then any animations in the 3D model with restart from the beginning whenever the marker is lost and then found again. For example, you could use this setting to ensure that animated models on the pages of a MagicBook always start playing from the beginning when the page is uncovered.

Images

Images can be directly added to the scene. They are displayed as textured planes which can be moved, rotated and scaled just like any other content. This is essentially a shortcut so that you can easily add an image without having to model a textured plane manually in a 3D modeling program, export it and then load it into BuildAR Pro. Most standard image file formats are supported, including JPG, PNG, TGA, GIF and BMP. Transparency is also supported for formats that contain an alpha channel.

Animated GIF files are supported and will loop continuously once loaded.

As with 3D models, the file to be used can be selected using the “Select” button, or by double-clicking on the item in the scene tree.

Movies

Like images described above, movie files can be added and will appear as textured planes.

Currently only QuickTime movies are supported. In order for this feature to work, you must have QuickTime installed on your system. QuickTime is included with the BuildAR Pro installer, so this should not be an issue.

The file to use can be selected using the “Select” button or by double-clicking the item in the scene tree.

There is an additional configuration panel where you can configure how the movie behaves when the marker it is attached to is found or lost. When either of these events occur movie playback can play, pause, stop or remain unchanged. The volume can also be changed. Using these two events it is possible to set up various scenarios. For example, when the marker is lost, the movie can pause, and when the marker is found, the movie can resume. Alternatively, the movie playback could be left unchanged, but the volume could lower when the marker is lost, and return to normal when the marker is found again. Again, this behaviour is useful for MagicBook applications where the movies on one page should stop playing when you move to the next page.

Text

The text content type allows you to specify labels which are drawn like 3D signs in the scene. Again, this is a shortcut which saves you from having to generate text objects as a 3D model.

Using the configuration panel you can specify the text to display, the color it should be, how transparent, and which font to use.

Primitive Objects

Primitive objects are basic objects that can be added to the scene without having to be modeled. The following shapes are available:

  • Box
  • Capsule
  • Cone
  • Cylinder
  • Sphere

Select the primitive type from the drop down box, and the rest of the panel will change to present the parameters relevant to that primitve type. For example, a sphere is defined by its radius, whereas a cylinder requires a radius and a height. You can also set the color and transparency of the object.

Sounds

Sounds can also be added to the scene. Currently WAV files can be loaded. The position of the sound is important because the sound is reproduced in 3D, meaning that if you move the marker to the left or right, the sound will seem to come from that direction. If the marker is far away the sound will get quieter, if it is close it will be louder, and so on.

The file to use can be selected using the “Select” button or by double-clicking the item in the scene tree.

If the “Show speaker” checkbox is checked, then the sound is shown within the 3D scene as a small speaker. This makes it easier to interact with because you can use the direct manipulation widget (described below) to move the sound around. The “Loop sound” checkbox will cause the sound to repeat endlessly if checked. This is useful for background ambient noises.

In the same way as movies, the way the sound behaves when the marker is found and lost can be configured.

Arranging Content

Each item of content you add to your scene can be independently positioned and oriented relative to the marker it is attached to, and scaled up or down. This allows you to build up small separate scenes on each marker. For example, you could add models for a table, chair and lamp, and arrange them to form a simple workspace.

BuildAR Pro provides two different ways to arrange objects: either by manually entering and adjusting values in a configuration panel, or by clicking and dragging directly on the objects in the 3D view. The two methods can be used interchangeably – simply use whichever method is easiest for what you are trying to achieve.

Setting Transformations Manually

Each content item in the scene has a configuration panel which is shown when that object is select. You can select an object by either selecting it in the scene tree or by clicking on it in the 3D view. Objects of different types (e.g. 3D model, Quicktime movie) have different configuration options, but they all share a common set of options for setting their 3D position, orientation and scale. Therefore, they can all be arranged using the same method.

Select the item you wish to adjust. The configuration panel will appear, with text input boxes for setting translation, rotation and scale.

  • Translation: Sets the X, Y, Z position of the object, in mm, relative to the center point of the marker.
  • Rotation: Sets the angles (in degrees) of rotation around the X, Y and Z axes.
  • Scale: Sets the X, Y, Z scale of the object.

There is also a button labelled “Normalize” which will attempt to position, orient and scale the selected object so that it “fits” well on the marker. If you have loaded a model and can’t see it, it may be sitting out of view, so you can try this option to bring it back onto the marker. However, if you have modeled an object with specific real-world measurements then you may want to keep these settings at their defaults. For position and rotation, default values are 0, but note that for scale, the default is 1 because a scale of 0 means an object will have no size at all.

Direct Interaction with the Transformation Widget

Rather than typing in values manually, it is also possible to use the more direct method of point-and-click. Once you select an object, a small set of axes will appear overlaid on the object in the 3D view. These axes are positioned at the origin of the selected object, and display the current X, Y, and Z axis directions as defined by the object’s current rotation. Bear in mind that this is relative to the marker, so as you move and rotate the marker, the axes will change position and orientation too.

The axes are actually interactive, and referred to as the transformation widget. When you move the mouse over the widget you can see various parts highlight, indicating that they can be clicked on to initiate an action. The widget operates in three modes: translation, rotation and scale. You can cycle between the modes by right clicking in the 3D view, or by selecting a mode from the toolbar.

In translation mode, each axis of the widget can be dragged to move the selected object along that axis. For example, if you want to move the object forwards along the Z axis then click and drag the blue axis in the direction it is pointing. Drag back again to go the other way. There are also small triangles near the origin of the widget that lie in the X, Y and Z planes. You can drag these to move the object around on that plane.

In rotation mode, the object can be rotated around each of the axes. When you drag one of the axes, the object will rotate only around that axis. To rotate freely around all axes you can drag the sphere at the origin of the widget.

In scale mode, dragging an axis will scale the object in that direction. This is called a “non-uniform scale” and results in the object becoming distorted. If you want to scale the object uniformly – just to make it either larger or smaller – you can drag the small cube at the origin of the widget instead.

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