Reflection contributes to the realism of an architectural rendering. Compared to standard ray tracing software, handling the reflection in a real-time rendering engine like Twinmotion is not always easy. This article explains how to enhance reflections in Twinmotion 2019 using the new feature “Reflection Probes” and shows you its intended use, such as creating a mirror.

How does default reflection in Twinmotion work?

Real-time engines like Twinmotion use Screen Space Reflection (SSR). That is, what you see in the reflection is what you see in the viewport. If an object does not appear in the viewport, it won’t appear in the reflection either.

Take a mirror as an example: when the camera is directly in front of the mirror, what is behind the camera cannot be seen. As there is no information in the reflection, Twinmotion shows the sky map instead. While the camera moves, more information is included in the view: the couch and vegetation outside the house; we can then see their reflections in the mirror. This is how the default reflections in Twinmotion work.

Introducing Reflection Probe

In order to surpass the limits of SSR and capture what cannot be seen in the Viewport into the reflection, Twinmotion 2019 introduces a new tool called “Reflection probe.”

Two Reflection Probes (Sphere and Box) can be found in Library > Volumes > Reflection

When adding a Reflection probe into the scene, Twinmotion calculates a 360° image from the center point of the Reflection Probe and puts the entire 360° image into the reflection of objects affected by the ratio of the Probe. As it is a one-shot capture, you can guess that the reflections inside a Reflection probe are not a real-time reflection.

Reflection Probe has the advantage that it doesn’t influence the framerate, no matter how many you put in the scene. However, since it is a fixed reflection, an animated path of characters or vehicles won’t be animated in the reflection.

Reflection probes’ settings

Box Reflection probe

Box Reflection probe is very good for interiors that have a box shape themselves. The vertical is straight compared to the Sphere Reflection probe.

• Enable: activate / deactivate the Reflection Probe
• Update: when moving the Reflection Probe, click on the update to recapture a 360° image
• Brightness: adjust the brightness of the 360° image captured inside the Reflection Probe
• Size: define the area where the reflection is net
• Transition: the reflection in the transition area fades out

Sphere Reflection probe

The Sphere Reflection probe can be used on an exterior scene where glass is transparent; it can also be used on a curved object like a chrome lamp or a car.

• Enable: activate / deactivate the Reflection Probe
• Update: when moving the Reflection Probe, click on the update to recapture a 360° image
• Brightness: adjust the brightness of the 360° image captured inside of the Reflection Probe
• Size: define the area where the reflection is net

Reflection probes resolution

It’s important to know that by default, the Reflection probes’ resolution for both Viewport and Export are set to x64. Depends on your needs, you may need to put a higher resolution to have a net reflection. In the case of a mirror, the resolution needs to be set to x1024 in the Viewport for real-time visualization and in Export for rendering media.

Export – Reflections update

The Reflections update option is unchecked by default. It is only useful when creating an animation with a time lapse. As reflections in the Reflection Probe are a fixed capture, the Reflection update option allows adapting the reflection to each time of the day in the animation.

*Attention: rendering time will be longer when this option is checked.

Examples of Reflection probes use

1. Use Reflection probe to improve interior reflections on glass areas

2. Use Reflection probe to create a mirror

3. Use multiple Reflection probes to improve exterior reflections on glass areas

For the exterior scene, one Reflection probe is not enough. You need to put one in front of each glass area.

When multiple Reflection probes are close to the same area, Twinmotion takes into consideration the closest Reflection probe.

4. Use multiple Reflection probes to improve interior reflections

Now it’s your turn to try! Download a Twinmotion 2019 fully functional trial version.

Share your work with us at twinmotion-gallery@abvent.com