Web-based Virtual Reality Environments

14. Environments and Other Components

The functionality present in A-Frame can be extended by external components. Many contributors to A-Frame have created and published components that we can use in our A-Frame scenes. In this chapter, we will explore a few to demonstrate how to use these external components and create more complex VR environments.

Loading Components

External components are programmed in JavaScript files that must be loaded into the HTML. This is typically done immediately after including the JavaScript file for the A-Frame framework in the <head> of the HTML:

<head>
    <title>Title</title>
    <script src="https://aframe.io/releases/1.2.0/aframe.min.js"></script>
    <script src="<JavaScript file for the component>"></script>
  </head>

After including the component's JavaScript file, we typicall access its functionality in one of two ways:

Environment Component

The Environment component allows us to quickly populate an A-Frame scene with visual elements.

The Environment component is loaded by inserting the following <script> element inside the <head>:

<script src="https://unpkg.com/aframe-environment-component@1.1.0/dist/aframe-environment-component.min.js"></script>

After the component is loaded, we can use an <a-entity> element (an <a-entity> is a generic entity in A-Frame without any default geometry) to automatically create large environments by adding the environment attribute.

<a-entity environment="preset: <name of the preset>"></a-entity>

The name of the preset can be one of: 'none', 'default', 'contact', 'egypt', 'checkerboard', 'forest', 'goaland', 'yavapai', 'goldmine', 'arches', 'threetowers', 'poison', 'tron', 'japan', 'dream', 'volcano', 'starry', 'osiris'.

Example 0500-environments-01 [new tab ] [source ]
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This element is used in a slightly different way from previous ones: we use a generic <a-entity> and them inside the environment attribute we define the various details of the environment (preset is just one). Also note that the syntax is parameter:value instead of parameter=value.

  1. Explore the different presets by running the example and changing the preset name.

Customizing the environment

The Environment component allows various customizations beyond the available presets. Let's take a look at two: Dressing and Play area.

Dressing

Dressings are additional objects scattered throughout the environment. Various parameters allow us to control these:

For example:

<a-entity environment="preset: goldmine; 
                       dressing: mushrooms; 
                       dressingAmount: 20; 
                       dressingColor: orange; 
                       dressingScale: 1"></a-entity> 
Example 0500-environments-02-dressing [new tab ] [source ]
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Play area

The play area is an area cleared of objects in the center of the environment. In this area we can then add our own 3D objects to create our scene.

The playArea parameter defines a radius where the ground is flat and no objects are automatically placed. This allows us to create an environment and then populate it with our own objects:

<a-entity environment="preset: tron; playArea: 10"></a-entity> 
Example 0500-environments-03-playarea [new tab ] [source ]
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Particle System Component

The Particle System component allows us to create what is usually called… particle systems: a number of small objects with pre-defined movement that live for a short time.

There is an incompatability between the Particle System component and A-Frame versions above 1.0.4. To use the Particle System component you should use A-Frame 1.0.4.

Particle systems are also an external component that requires the following <script>:

<script src="https://unpkg.com/aframe-particle-system-component@1.0.x/dist/aframe-particle-system-component.min.js"></script>

Once we include the script, we can use a generic <a-entity> and configure the particles in the particle-system attribute, in a similar way as we did with the Environment component.

The most simple way is to use a particle system preset. There are presets for rain, stars, dust, snow, and colors.

<a-entity particle-system="preset: rain"></a-entity>
Example 0500-environments-04-particles [new tab ] [source ]
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In the example above, we are using algo the Environment component, but we can use the Particle System without the Environment.

There is a slight incompatibility between Environment and Particle System. For them to work together you need to disable the fog in the Environment:

<a-entity environment="preset: contact; 
                       playArea: 10; 
                       fog: 0">
</a-entity>
  1. In the example above, try changing the preset (we may need to adjust the sky's color to see the particles).

Customizing the Particle System

Color and Size

To change the particle's color just add the color parameter to its configuration (note that just like in the Environment component, different parameters must be separated by a semi-colon ;). To change the size, we use the size parameter:

<a-entity position="0 2.25 -15" particle-system="preset: rain; color: red; size: 5"></a-entity>
Example 0500-environments-05-particles-color [new tab ] [source ]
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Making a fountain

To make a particle system that resembles a fountain we need to control additional parameters like the velocity, and texture applied to the particles:

<a-entity position="0 1.25 -15" particle-system="velocityValue: 0 12 0; velocitySpread: 0 0.1 0; texture: https://cdn.rawgit.com/IdeaSpaceVR/aframe-particle-system-component/master/dist/images/raindrop.png; color: red; opacity: 1"></a-entity>
Example 0500-environments-07-particles-fountain [new tab ] [source ]
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Oceans

Oceans are also an external component, so we need to add another <script> tag to our code (inside the <head> element):

<script src="//cdn.rawgit.com/donmccurdy/aframe-extras/v4.0.2/dist/aframe-extras.min.js"></script>

Once we add the script, we have access to another primitive: <a-ocean>:

<a-ocean position="0 0 0" width="10" depth="10" opacity="1"></a-ocean>

This primitive creates a rectangular surface that is animated, and mimics the ocean waves. We can control the position, and size of this surface with the position, width, and depth attributes.

We can also control the speed and amplitude of the waves with the speed and amplitude attributes.

Example 0500-environments-08-oceans [new tab ] [source ]
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Combining Everything

Example 0500-environments-10-environ-ocean-fountain [new tab ] [source ]
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Exercises

Environments-01

Create a forest environment using the Environments component. Add cylinder textured with a tree bark texture

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Environments-02

Using the Ocean component, create a scene with a "lake" and a boat on it. Use your imagination to create a boat-like object using simple shapes.

Environments-03

Using the Particle System and the Environment components, create a scene with a forest and strong wind that carries particles horizontaly across the screen.

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References

Comments

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Copyright © 2020 Jorge C. S. Cardoso jorgecardoso@ieee.org