Thea for Rhino can render interacively in both Thea Darkroom and Rhino's Viewports.
Rendering interactively in Thea Darkroom is useful for systems with multiple monitors as it allows you to have Thea Darkroom running in a separate monitor while working on your project. To start Interactive Rendering, make sure that the option IR (Interactive Rendering) is active and click on the start button.
Thea is capable of rendering interactively inside Rhino's viewports. To start rendering, click on the Start button of the Thea Toolbar. At any time, you can either click on the Stop button to stop Interactive Rendering or the Save image button to save the image that is currently being displayed in the viewport.