Environment Probe

Overview

Environment Probe is a great thing to increase performance, decrease the number of materials and make the life of content designers easier.

Environment probes use cubemaps that were baked (or grabbed with a special tool). This cubemap will play the role of the reflection and the light simulation. Here is an example:

We have two houses with different color of the interior and put same objects (with reflection material, for example, metal) into these houses. What will happen?

If we don't speak about the dynamic reflections, you'll need to reflect the interior on each object. But interiors have different ambient color, and that is why you'll need to create 2 different materials for them. Not optimized at all.

Environment probes remove this flaw. Once you added an object, you don't think about the reflection material for it. The environment probe will map the cubemap to the object.

There is a difference in mapping cubemaps to transparent and non-transparent objects:

If an object is transparent, the environment probe will map the cubemap only if the entire object is inside the radius of the environment probe. Otherwise, the object won't be affected by the environment probe at all.
If an object is non-transparent, the environment probe will map the cubemap to any part of the object which is inside the radius of the probe.


Transparent object illuminated by environment probe	Non-transparent object illuminated by environment probe

If you put several environment probes that illuminate a non-transparent object (rendered in the deferred pass) their cubemaps will be blended smoothly. Here is an example, a long corridor which has walls painted in different colors.

We put two environment probes and both of them affect the object (when the object will be in the intercrossing area). When you have large locations, you should use several environment probes instead of one to make the final image more realistic.

The SSR (Screen Space Reflections) effect makes the final image more realistic, because it appends reflections that cannot be baked into cubemaps. Using environment probes and SSR is a great method for pretty fast imitation of reflections with dynamic lighting.

Multiple Environment Probes for Transparent Objects

The Multiple Environment Probes option set for a transparent object (rendered in the forward pass) allows several environment probes illuminate the object and map their cubemaps to it.

When the option is disabled, only the last set environment probe will illuminate the object. At that the entire object must be inside the radius of the environment probe. Otherwise, it won't be affected by the enviroment probe at all.
When the option is enabled, the object will be lit by all of the environment probes: each probe will affect the part of the object, which is inside the probe. Cubemaps of the environment probes will be blended in the intercrossing areas.


Multiple Environment Probes is off: only the left cubemap is mapped to the object	Multiple Environment Probes is on: both cubemaps are mapped and blended

Adding Environment Probe

To add an Environment Probe object to the scene via UnigineEditor, do the following:

Run UnigineEditor.
On the Menu bar, click Create -> Light -> Environment Probe.
Place the environment probe.
Grab the cubemap texture for the environment probe. You can grab it in the Light tab of the Environment Probe's node or you can grab it by using Grabber.
Notice
To bake lighting to the environment probe properly the following sequence of actions is recommended:
1. Set light color to black and click Grab. Thus, you'll get the first GI bounce.
2. Set light color back to white and click Grab againg. Thus, you'll get the second GI bounce.
Setting black color first, helps to hide ambient lighting and reflections from the global environment at the moment of baking.
Adjust the environment probe settings.

Notice

You can't bake "real" lights (LightOmni, LightProj, etc.) to an environment probe. Maximum you can do here, is place spheres with emission materials instead of lights, adjust emission intensity and then bake lighting. However, the result will look worse than you'd have with real lights.