How to render a raytraced image by the end-user.

Hi,

I'm trying to find a way to render a really high quality raytraced image by the END-USER.
I already looked into OctaneRender, which is REALLY close to what I'm looking for, but it seems I can only generate the raytraced image as a developper.

Here is my full concept :
-The user would load up my program. He sees a scene, and can look around with the mouse. And when he is satisfied with what he sees, he pauses everything, and start a raytraced render of the scene, which will be saved on his hard drive. I don't care about the performance or the framerate. What I want is an almost real-life looking picture. The user could start the render, leave his computer and come back 1 hour later to see the result.

Is this something that has already been done ?
I'm having trouble searching the internet, because I keep finding results about the announcement that Unity and NVidia are releasing a real-time ray tracing solution. Which is NOT what I need. As I said, I don't care about performance or framerate.

Thanks for your help!