POV-Ray is a free open-source ray-tracing program which accepts a scene description in a textual programming-like language and renders an image with lighting, shadows, reflections, refraction and other visual effects calculated automatically.
POV-Ray (Persistence of Vision Raytracer) renders scenes described by a scene description language. Conventional computer graphics techniques (scan-line techniques) loop through each object to be rendered and calculate where and how to draw them on the image. In contrast, ray tracing loops through each pixel in the image, and fires a ray from the viewpoint (the eye) back through the pixel into the world to find out what object the ray will eventually hit. The color of that object is assigned to the pixel. If the object has a reflective surface, another ray is fired off in the appropriate direction and a component of its color is added to the pixel. Similarly, surfaces that refract light generate another ray through the transparent material and a component of the color it calculates is also added to the pixel.
POV-Ray is available from www.povray.org and is free to use. The program itself cannot be embedded into commercial software without permission but the images created are owned by the creator of the scene file. See www.povray.org for details on the licensing.
