Environments
Environments
Embedded Files
In Unity, the environment is the color or texture used as background when the camera ray doesn't hit any geometry in the 3D scene. The environment in Predict Engine works exactly the same, but it is important to notice that the Predict environment is actually lighting the scene : it is an image-based lighting.
Without specific settings, the Unity default camera defines RGB non polarized environments (see the Overview section for more details). To create a spectral and/or polarized environment, you must add the UVR Skybox Settings component to your camera.
The UVR Skybox Settings component enables you to define the spectral intensity of the environment. The available intensities depend on the Unity Camera "Clear Flags" field :
For a solid color environment, the environment is defined by ambient lighting settings,
For a skybox environment, the environment can be defined by a panoramic texture or by CIE default presets.
All types of environments are explained in detail in the sections bellow.
You can define a global environment that affects all cameras in the scene.
To do so, place the UVR Skybox Settings component anywhere in the scene, on an object that does not have a Camera component. An additional toggle will appear to "use as default for all cameras". If true, these settings will be used for all cameras that do not have an UVR Skybox Settings component.
If the GameObject has a Skybox component, the UVR Skybox Settings component describes an envmap (equivalent to the Camera 'skybox' clearflag). Otherwise, the component describes an ambient environment (equivalent to the Camera 'solid color' clearflag).
You can instantiate such default environments via the right click menu in the Hierarchy PredictSuite/Light/Environment.
Unity Tutorial : Introduction to Lighting and rendering (Section 8 : Ambient Lighting)
Unity Tutorial : Using Skyboxes
If a camera has a UVR Skybox Settings component, Unity’s Skybox or Volume component will be ignored in Predict Engine.
Ambient lighting
Ambient lighting
If the Unity camera "Clear Flags" field is set to "Solid Color", the Predict environment is defined by the spectrum of the sky and its polarization.
The radiance of the sky spectrum can be modulated by :
A scaling coefficient,
A luminance or radiance value : in this case, the coefficient applied to the spectrum is automatically computed so that the luminance of the light reaches the required value,
An illuminance or irradiance value : in this case, the coefficient applied to the spectrum is automatically computed so that the illuminance of an horizontal plane in the scene reaches the required value,
A preset value.
The polarization of the sky can be defined using a preset definition, the degree/ellipticity/orientation of the polarization, or reduced stokes vectors. See the polarization section for more details on polarization.
The color of the Unity environment will be automatically set to match the Predict environment.
Panoramic environments
Panoramic environments
If the Unity camera "Clear Flags" field is set to "Skybox", the Predict environment can be defined by a panoramic texture.
The panoramic texture should contain RGB data (any format) and/or spectral data (EXR format). If it is given in the EXR format, the texture can also contain the polarization information of the sky. Its irradiance can be modulated by :
A scaling coefficient,
An illuminance or irradiance value : in this case, the coefficient applied to the sky is automatically computed so that the illuminance of an horizontal plane in the scene reaches the required value,
A preset value.
Panoramic environments should be defined using the NESWN convention : with a rotation of 0, the North will be facing the -X axis in Unity.
UVR procedural sky generator Predict Sky enables you to generate procedural skies for a given position on earth, date, time and sky conditions. The output texture contains the intensity, polarization and sun data of the environment.
If you reference a Predict Sky texture in a panoramic environment, a "Sun" section will appear bellow the Sky section. The section contains details on the luminance of the sun, its radius and the turbidity of the environment.
If the sky texture contains RGB data, the skybox of the Unity environment will be automatically set to match the Predict environment.
You can download a demo set of Predict Sky environment from the download menu, see the Default Assets section for more details.
CIE environments
CIE environments
If the Unity camera "Clear Flags" field is set to "Skybox", the Predict environment can be defined by a CIE preset : the CIE has defined a set of 15 preset environments and an additional overcast sky (id = 16). You can find more details on each environment here and here. Each environment is defined by its id and by the position of the sun in the sky.
In addition, you can also define the (il)luminance of the sky and of the sun as well as the radius of the sun.
http://andrewmarsh.com/software/cie-sky-web/
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