raytracing-ruby/Camera.rb at master · motorailgun/raytracing-ruby · GitHub

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require_relative './Point3D'

class Camera
    attr_reader :viewport_height, :viewport_width, :focal_length, :origin

    def initialize(aspect_ratio: 16.0 / 9.0,
                  focal_length: 1.0,
                  origin: p3d(0.0, 0.0, 0.0),
                  v_fov: 90,
                  aperture: 2.0,
                  look_from: ,
                  look_at: ,
                  vec_view_up: ,
                  focus_distance:
                )

        raise ArgumentError.new("Origin must be kind of Point3D") unless origin.kind_of?(Point3D)

        tant = Math.tan(v_fov * Math::PI / 180.0 / 2)
        @viewport_height = 2.0 * tant
        @viewport_width = aspect_ratio * @viewport_height

        @aspect_ratio, @focal_length = aspect_ratio, focal_length
        @origin = origin

        @w = w = (look_from - look_at).unit_vector
        @u = u = vec_view_up.cross(w).unit_vector
        @v = v = w.cross(u)

        @origin = look_from
        @horizontal = focus_distance * @viewport_width * u
        @vertical = focus_distance * @viewport_height * v
        @lower_left_corner = @origin - @horizontal / 2 - @vertical / 2 - focus_distance * w

        @lens_radius = aperture / 2.0
    end

    def get_ray(u, v)
        rd = @lens_radius * random_in_unit_disk
        offset = @u * rd.x + @v * rd.y

        ray(@origin + offset,
            @lower_left_corner + u * @horizontal + v * @vertical - @origin - offset)
    end

    private
    def random_in_unit_disk
        loop do
            p = v3d(rand(-1.0..1.0), rand(-1.0..1.0), 0)
            next if p ** 2 >= 1
            return p
        end
    end

end