we just released Thea for Rhino v1.5.03 with many improvements.
If you are not familiar with Thea, it is a rendering solution offering high quality unbiased & biased rendering and can deliver very fast results using its GPU engine (currently working with NVidia GPU cards but it is not required as it can work also very efficiently on CPU).
In the past months, we have given an intense effort for integrating Thea in Rhino, with fast interactive rendering (even inside viewport!), ground plane and shadow catcher, custom material visualization, clipping planes and many other features. Take a look at our showreel video here
For those interested, you can find more details about the integration and you are also welcomed to download the evaluation version at our Rhino dedicated page: