In Thea Render, the environment settings are global, and they refer to the illumination that comes from the sky. It also describes how the surrounding environment affects the scene in general. In Cinema 4D you can have multiple Sky objects in your hierarchy, but only the first one will be taken into consideration to be transferred into the engine. The correct way to setup the environment settings in Thea For Cinema 4D is by creating a Sky object and apply a Thea Sky Tag to it. All the necessary configurations in environment can be achieved in the tag.
The environment illumination is described with two types in Thea Render: Sky and Image Based Lighting (IBL). In Sky mode you are able to parameterize the physically-based sky model of Thea Render, while in IBL you are requested an Image that will be used to illuminate the scene (HDR preferably).
Other than the illumination parameters, you can also set the properties of your sun.
Show Sun in render
It is used to make the sun visible in your image. In Sun Mode you can choose any of Infinite Light Object, Location/Time and Sun Position.
In Environment Mapping group, you can configure the Background, Reflection and Refraction of your environment based on images. If these parameters are left empty, your IBL image will be used by default (if IBL is set as illumination mode).
Last, Global Medium group refers to the medium surrounding our scene. We usually need it to produce foggy effects inside Thea Render.
Finally, using the Content browser, you can easily create Sky objects with Thea Sky Tag attached. Simply launch the content browser, select the "Skies" tab and double click any HDR image. A sky object will be created in the hierarchy along with a Thea Sky Tag attached to it. The selected Image will be set as IBL automatically.