Sorry to hear that you're feeling baffled and befuddled using Terragen.
It appears that in your example project, the Sphere 01's Default shader has an Image Map shader assigned to its Opacity function, the same image applied to its Opacity Image parameter, and an Opacity value of 0.6125.
The first thing to understand is that the value of all three of these parameters are multiplied together in order to determine a value for a given point on the surface being sampled by the renderer. Many of the Default shader's parameters work this way. For example, the Base Colour, Colour Image, and Colour Function parameters work in this manner when determining the colour value of the point being sampled by the renderer.
That being said, the surface's opacity will still be rendered as I described in this previous post:
https://planetside.co.uk/forums/index.php/topic,30900.0.htmlTo summarize, the opacity of the Default shader on the sphere's surface will be either fully opaque where the opacity value is 0.5 or greater, or be completely "transparent" where the opacity value is below 0.5. In those transparent areas, the shader network connected to the Default shader's Main Input will be revealed, and if nothing is connected to the Main Input then that area will be black.
