Mandelbulb fractal 3D in pure Javascript based on GPU.JS
Input parameters (left-handed coordinate system):
- camera (eye) position at point
- target point where camera looks
- camera vertical normalized vector which idicates where is up and were is down (not shown on picture, usually equal [0,1,0]).
- field of view (slacar value, for human eye 
)
- number of pixels on screen width
- number of pixels screen in height
IDEA: lets find position of center of each pixel 
which allows us to easily find ray which starts at 
and go thought that pixel. To do it we find first 
and find others by move on vievports plane.
ASSUMPTION: 
which simplify calculations but not change the result (because 
is normalized and viewport size is determined by 
and 
)
PRECALCULATIONS: First we calculate normalized vectors 
from picutre (which are parallel to viewport plane and give as direction for shifting)
notice: 
, then we calculate viewport size divided by 2 and including aspect ratio 
and then we calculate shifting vectors 
on viewport 
direction and viewport left upper pixel
CALCULATIONS: notice that 
and ray 
so normalized ray is
