Here is an image with the plane 1 removed. I've inserted a bryce cube with default texture into the center. there is no flat ground just the projection of the hdr sourced jpg on the sphere. This first one is diffusion 100 ambience 19 with shadows off in the materials and bryce sunlight shining through the sphere. The sun controls appear flipped. I had to set the sun position in the upper north quadreant of the control in order to light the south side of the cube. you can also see shadows around the edges where the dome appears dull. Turning off link sunlight to view does not cure this.