focal blur camera
// focal blur camera
camera {
location <0.0, 2.0, -5.0>
look_at <0.0, 0.0, 0.0>
right x*image_width/image_height
aperture 1.0 // [0...N] larger is narrower depth of field (blurrier)
blur_samples 10 // number of rays per pixel for sampling
focal_point <0,1,2> // point that is in focus <X,Y,Z>
confidence 0.95 // [0...<1] when to move on while sampling (smaller is less accurate)
variance 1/200 // [0...1] how precise to calculate (smaller is more accurate)
}