The eye: a position and a rotation (looking down its -Z with +Y up), a vertical field of view in radians, and near and far distances. snap: true places it without interpolating from where it was on the previous tick.

viewport is the part of the frame the view is drawn into, {x, y, width, height} as fractions of the frame from its top left; the rest of the frame is black under the overlay. aspect is how wide the viewport shows on screen against its height, for frames whose pixels are not square; nil takes it from the viewport's pixels. resolution, {columns, rows}, shows the view as that many blocks across and down its viewport, each the colour at its centre; nil shows every pixel.