lighttroupe/luz-next

class GLCamera
    POSITION_ANIMATION_TIME = 0.2
    PROGRESS_PER_FRAME = 0.12
    MIN_DISTANCE = 0.001

    include Drawing

    def initialize
        @position = Vector3.new(0,0,0.5)
        @look_vector = Vector3.new(0,0,-1.0)
        @up_vector = Vector3.new(0,1,0)
        @new_position = @position.dup
    end

    def using
        GL.Translate(0,0,0.5)        # HACK: undo built in translate

        if @new_position != @position
            towards = @new_position - @position
            @position = @position + (towards * PROGRESS_PER_FRAME)
            #$gui.positive_message "stop" if towards.length < MIN_DISTANCE
            @position = @new_position if towards.length < MIN_DISTANCE
        end

        GL.SaveMatrix {
            GLU.LookAt(@position.x, @position.y, @position.z, @position.x+@look_vector.x, @position.y+@look_vector.y, @position.z+@look_vector.z, @up_vector.x, @up_vector.y, @up_vector.z)
            yield
        }
    end

    #
    # Vector helpers
    #
    def left_vector
        @up_vector.cross(@look_vector)
    end

    #
    # Movement
    #
    def move_forward(amount)
        @new_position = @new_position + (@look_vector * amount)
    end
    def move_left(amount)
        @new_position = @new_position + (left_vector * amount)
    end
    def move_up(amount)
        @new_position = @new_position + (@up_vector * amount)
    end
end