Depth Of Field test

[eiffie]

I think it will be difficult to get DOF effect using DE but of course it is possible. You have made first good step with adaptation of distance threshold according to focal distance. But now is bigger problem. Edge of detail which is out of focus should be transparent. It means that when program find edge which should be blur, must remember colour of this element and calculate proper transparency (according to distance to the fractal surface). Next program should still trace ray to find deeper edges (and also remember these) until find solid fractal surface. I hope my explanation is understandable - I still has some problems with my English 

This is exactly what needed to be done! I have been making some attempts at it here:
http://www.fractalforums.com/programming/fast-fake-montecarlo-for-raymarching-(not-sure-what-to-call-it-yet)/

Wish I had paid more attention to this thread at the time.