I use rhino for making as well as rendering my cad models. The renders turns out to be nice for web but, for other things like presentations, my renders lack a crispness and quality. so, I wanted to know that can we make rhino renders in high definition? and is Yes, then How...
It depends on what software are you using to make the renders. If you use the rhino's default render, you're gonna have a bad time because it has a very poor quality on materials, textures and environments.
I recommend you to use keyshot or Vray.
Some tips to improve the quality would be like:
Try to increase the image size (640x800 to 1920X900) or something like that.
Increase the subdivisions on your materials.
Use a correct ilumination setting on you render.
Hope this help.