VR Best Practices

Virtual Reality (VR) is an immersive medium creating the sensation of being entirely transported into a virtual or digitally reproduced real three-dimensional world. It can provide an lot more convincing experience than screen-based media, and has its peculiarities that should be taken into account.

The best practices described in this article are intended to higlight some key points that you should be aware of when developing a VR project and help you produce content ensuring a safe and enjoyable VR experience for users.

Thinking about VR developers we created the VR Template demo enabling you to jump straight in and start creating projects of your own.

We recommend to use this demo as a basis for your VR project. Here you'll find a set of 3D models of all popular VR controllers, as well as implementation of basic mechanics such as grabbing and trowing objects, pressing buttons, opening/closing drawers and a lot more.

The world in this template project has its settings optimized for best performance in VR and includes a .render asset that can be loaded at any time by simply double-clicking on it in the Asset Browser to reset any changes you made to default optimized values.

Perception of scale of objects around you is likely to be the key point that makes the difference between VR and a flat picture on the screen. Your models might look "right" on the screen, but in VR you'll surely notice if a table has somewhat unusual height, the size of your chair as well as sizes of objects on your table are wrong.

To deliver the best user experience in VR you must ensure that everything in your world has a correct scale. Failing to meet this requirement may lead to all kinds of sensory issues for users, and could even result in Virtual Reality Sickness.

You can use the following tips to avoid mistakes mentioned above:

• Create all your models keeping their scale as close to real as possible. For example, you should measure the height of your table, windowsill and chair. Having just these parameters and using them as a base to determine the size of your models, will make them realistic.
• Remember, that UNIGINE's unit, like in many other engines, is equal to 1 meter, while in many Digital Content Creation tools it is equal to 1 cm by default for convenience. You can adjust the scale of your 3D models if necessary when importing them by setting the scale factor in geometry import parameters greater or less than 1.
• Test your content in VR. This approach will be useful in any case, as we are not just creating virtual copies of existing objects, sometimes it may be necessary to create something new, something that doesn't exist. Such new created objects may require additional scale adjustments to ensure realistic look. It is recommended to create a dummy model first, put it into your world and check it in VR, to ensure that all dimensions are ok. As you're done with the dummy, you may proceed to your 3D model. This approach will help you to avoid painful adjustment of your 3D model's proportions at the final stage.
• You can use VR controllers as references for measurement. Imagine, you have a Vive controller in your hand and see its size relative to other objects around you. The 3D model of this controller in your virtual world has the exact scale of the original, So, you can import this model to a DCC tool (3DS Max, Maya, etc.) and use it as a reference when creating other objects.

Please keep in mind that objects in VR are viewed best when they are in a range between 0.75 and 3.5 meters from the player's camera.

Virtual Reality Sickness is quite similar to motion sickness, it occurs when using VR headsets. It can significantly affect or even ruin user's VR experience, and may be a barrier to the effective use of VR training tools.

Follow the recommendations given below to reduce the risk of VR Sickness and ensure that you users will have a pleasant VR experience:

• You must maintain framerate equal to or greater than the HMD's display refresh rate. Ideally, it should be kept a little bit higher to make sure you always stay above. Lags and dropped frames produce judder which is discomforting in VR. So, make sure to optimize your project as much as possible.
• The worst thing you can do to your user in VR is to display cinematic cutscenes or take control of camera movement in conflict with the user’s real-world self-motion. So, don't do that.
• The Field of View (FOV) must match the physical geometry of the headset and lenses. Otherwise, the world will look warped as you turn your head, which may cause discomfort and nausea. So, FOV value should be set automatically via the device's SDK and internal configuration. Avoid overriding it manually yourself and do not let users change it.
• Avoid using camera bobbing effect to simulate walking (typical for the most first person games). Moving the camera up and down is annoying, it breaks VR experience and causes VR Sickness.
• Zooming in or out with the camera is not recommended, as it can induce VR Sickness, particularly if doing so causes head and camera movements to fall out of 1-to-1 correspondence with each other.
• Remember, that any acceleration creates a mismatch among your visual, vestibular, and proprioceptive senses. The term acceleration here refers to any change in the motion of the user, whether in direction or speed. Slowing down or stopping, turning while moving or standing still, and stepping or getting pushed sideways are all forms of acceleration. Make such conflicts as short (preferably instantaneous) and infrequent as you can. Have accelerations initiated and controlled by the user whenever possible.
• Shaking, jerking, or bobbing the camera will be uncomfortable for the player. So, do not shake the camera to emphasize an event (e.g. a grenade explosion), it may make sense in a screen-based media, but not in VR.
• Avoid stairs, use lifts instead, as moving quickly up and down the stairs can be very disorienting for the player.
• Developers are often used to using VR devices and may not notice or feel something that other person would. So, to make sure that your application does not cause VR Sickness you should check it as much as possible, engaging as many different people as you can.

Please note that the points listed above do not consitute a complete list of root causes for VR Sickness. It is intended to give you a basic idea of what might cause users of your VR application to feel sick.

Your art assets will look very different in the headset than on your computer screen. Z-fighting, seams, and other errors will always be more apparent. You also have to worry about what textures will make people sick. You should probably avoid high contrast textures and highly saturated colors as anything too bright or busy can give your player a headache and/or make them sick.

When making content for VR you should keep in mind that users will be able to look at it from various points of view and will interact with it like they would in real life. Generally, you should be testing your assets whenever you have doubts and even when you think you don’t. You should always be testing. So, there are a number of basic recommendations:

Render Settings

Screen-Space Effects

Antialiasing

Lighting

Decals

Transparency

Clouds and Sky

Geometry

Monitoring Performance