so why does it use multi-layer perceptron? is it the same as ANN? why not calling it ANN? Does it have activation?
There is another thing I don't understand. Traditional volume data is a map of position to density (or color). There doesn't seem to be the need for a direction as an input.
Why does the network need a direction? Why can't we get a density (opacity) and a color given a position?
Answered most your other questions below in another comment.
> and what are z(t) r(t) in equation 5,6?
r(t) is a position in 3D space along a camera ray of the form, r(t) = origin + t * direction.
z(t) is the output of our first MLP. Think of it as a 256-dimensional vector of uninterpretable numbers that represent the input position r(t) in a useful way.
There is another thing I don't understand. Traditional volume data is a map of position to density (or color). There doesn't seem to be the need for a direction as an input.
Why does the network need a direction? Why can't we get a density (opacity) and a color given a position?
and what are z(t) r(t) in equation 5,6?