You can specify Environment maps as an environment for lighting, or an environment for the background. Apart from lighting an Environment with an HDR image, you can also specify a different Environment for the background, you can also see that background in reflections.
If specified, this Environment is used for reflections, refractions, and all camera rays that leave the scene, and the regular environment is used for the direct light calculation.
The Visible Environment overrides the normal environment in some specific use cases, giving more control over the render's final look. If a Medium is configured in the Environment, OctaneRender® ignores the Medium when it uses the Environment as a Visible Environment.
Environment nodes (both Daylight and Texture environments) have extra options to control the Environment's behavior when used as the Visible Environment. When you use the node as a normal environment, OctaneRender® ignores these options.
The Visible Environment parameters are accessible from Octane Render Target Actor by clicking on the Details panel, then clicking on the Visible Environment rollout (figure 1).
Figure 1: The Visible Environment set to a a solid white texture, overriding the HDRIAn image which presents more than 8 bit per color channel unlike most common image formats. image used to light the scene in the Environment rollout