Level design

Despite all of the technical options available to help minimize aliasing, careful level design is still vital in helping reduce aliasing artifacts. Poor choices in level design can make every technical solution redundant, so wise decisions in level design still play a critical role in minimizing aliasing.

When creating geometry for a scene, care must be taken when modeling the edges of meshes to avoid sharp or sudden edges. For example, a staircase that has flat edges on each individual step can create aliasing if the viewer rotates their head.

However, the individual steps themselves can also be the cause of aliasing when a staircase is viewed from a large distance. Each step becomes a thin object in the distance that can flicker as the viewer moves around.

The following image shows an example of the different levels of aliasing that is produced when you use stairs, versus a ramp:

Video comparing aliasing on stairs and ramps

The following video shows an example of the different levels of aliasing that is produced when you use stairs, versus a ramp:

https://developer.arm.com/graphics/videos/ramp-vs-stairs-aliasing-example

Whenever possible, use smooth, round shapes in place of those shapes with hard edges or bevels. Thin objects, such as wires or cables, have a propensity to cause substantial aliasing when they are viewed from a distance. This is because thin objects are rendered as lines, causing aliasing to occur.

Careful consideration must be made on the use of metallic materials. These should be minimized where possible, as metallic objects produce specular effects when lit. These specular effects flicker as the viewer moves, resulting in aliasing. Therefore, the use of matte materials is preferred.

The following image shows a comparison between the aliasing that is caused by metallic and matte materials. The top-half of the image shows a metallic material, while the lower image shows the matte equivalent.

Implement scene lighting with caution, as bright shiny lights result in specular effects appearing on the lit objects. Doing so can cause specular aliasing which is very noticeable. The eye is drawn to the ‘flashing’ of the pixel as the specular effect appears and disappears between frames.

To avoid expensive real time lighting calculations and reduce the presence of lighting artifacts such as banding, lighting can be prebaked when the scene is built. To do this, scenes must be designed so that they are appropriate for prebaking which requires few moving objects and no live day or night cycle.

Utilizing light probes can help to minimize the quantity of prebaking required and they are especially advantageous in VR with 6 degrees of freedom.

Reflections require more caution in VR than is typical than in more common use-cases. Techniques like screen space reflections are too computationally expensive for VR. Therefore, other techniques must be employed for reflections. Possible techniques for objects that require high-quality reflections include reflection probes and cube maps, as reflections can be pre-rendered for use at runtime.

To help hide aliasing, particle effects can be deployed, such as fog or smoke. These techniques, that have long been used to hide short render distances, can also be used to cover aliasing that is caused by objects in the distance.

In the following figure, the right-hand image demonstrates how aliasing is reduced after the addition of a particle effect:

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