One of the best ways to convey a large sense of scale is to have an atmospheric haze into the distance. Since Octane Render 2.x does not contain true volumetrics for its sun and sky system, I created the effect using a massive sphere with normals pointing outwards, and a small sphere surrounding the render camera lens with normals pointing inward. When these surfaces are both assigned a specular shader that contains internal volume scattering with a refractive index set to 1, the camera is basically looking through a massive volumetric medium. In this case, the density is low enough to reveal the brightest stars in the background.
A wireframe of the scene, which contains a little over 9 million polygons, and has a very wide scale between the smallest objects and the overall scene size. The mushroom trees and fungus grass are propogated with Maya's MASH environment node, and use several levels of detail based on the rendered camera position.
Octane Node-based shader group for the ground. It uses a mix material to combine two glossy materials based on a grayscale paint map based on the ground's UV's, so some areas have a rocky appearance while others are more rocky and mountainous. All shading groups in the scene contain diffuse/color maps multiplied by ambient occlusion maps, normal maps, and specular strength and/or roughness maps multiplied by reflective occlusion maps. All shaders, including specular/dielectrics, glossy, and emissive, all are physically based and follow conservation of energy.
