What are some alternatives?
When comparing Sunflow Rendering System and V-Ray, you can also consider the following products
RenderMan - Advanced Technology from Pixar Animation Studios for Rendering VFX and Animation
Keyshot - KeyShot 3D rendering and animation software is the fastest, easiest way to create amazing, photographic visuals of your 3D models. Enter your search in the box aboveTryYour download of KeyShot is only moments away.
appleseed - appleseed is an open source, physically-based global illumination rendering engine primarily designed for animation and visual effects.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Cinema 4D - Cinema 4D is a 3D modeling, animation, motion graphics and rendering application.
Mitsuba - Mitsuba is a research-oriented rendering system in the style of PBRT, from which it derives much inspiration.