Our goal with Tachyon Render is not only to have high quality real-time materials but also to provide a workflow that is as familiar as possible.
One very important aspect the materials. We want to be able to create a wide range of different materials that match what you can create with Cinema 4D's reflectance system. Sure, there are limitations with real-time rendering when it comes to layering complexity but the basis needs to be familiar.
To make sure we hit this goal as closely as possible we are frequently making material comparisons with Cinema 4D's own renderer. Below you see an example where we compare the glossiness / roughness settings.