A method of rendering an image to be displayed on a display device installed in a vehicle and including a display panel, the method comprising: outputting a test image, wherein the test image includes two straight lines that intersect each other; distinguishing a two-dimensional, 2D, display area from a three-dimensional, 3D, display area based on the test image, wherein the two straight lines are clearly displayed in the 2D display area and not clearly displayed in the 3D display area; determining which one from among the two-dimensional, 2D, display area and the three-dimensional, 3D, display area includes a current pixel, the 2D display area displaying a 2D image comprising at least one from among text and a guidance indication to provide operating information that relates to the vehicle on a windshield of the vehicle and the 3D display area displaying a 3D image of a route guidance indicator to guide a traveling path of the vehicle, wherein the route guidance indicator is pictorially matched to a road from a viewpoint of a driver and wherein a 3D optical device comprising a parallax barrier and/or a lenticular lens is located on or above the 3D display area of the display panel and determines a ray direction of the image; performing a 2D rendering operation at a position of the current pixel when the current pixel is included in the 2D display area not corresponding to the 3D optical device; and performing a 3D rendering operation at a position of the current pixel when the current pixel is included in the 3D display area corresponding to the 3D optical device based on tracking a right eye position and a left eye position of a viewer; and generating a composite image that includes a combination of the 2D image located in the 2D display area and the 3D image located in the 3D display area as a result of the performing of all the 2D rendering operations and the performing of all the 3D rendering operations. outputting a test image, wherein the test image includes two straight lines that intersect each other; distinguishing a two-dimensional, 2D, display area from a three-dimensional, 3D, display area based on the test image, wherein the two straight lines are clearly displayed in the 2D display area and not clearly displayed in the 3D display area; determining which one from among the two-dimensional, 2D, display area and the three-dimensional, 3D, display area includes a current pixel, the 2D display area displaying a 2D image comprising at least one from among text and a guidance indication to provide operating information that relates to the vehicle on a windshield of the vehicle and the 3D display area displaying a 3D image of a route guidance indicator to guide a traveling path of the vehicle, wherein the route guidance indicator is pictorially matched to a road from a viewpoint of a driver and wherein a 3D optical device comprising a parallax barrier and/or a lenticular lens is located on or above the 3D display area of the display panel and determines a ray direction of the image; performing a 2D rendering operation at a position of the current pixel when the current pixel is included in the 2D display area not corresponding to the 3D optical device; and performing a 3D rendering operation at a position of the current pixel when the current pixel is included in the 3D display area corresponding to the 3D optical device based on tracking a right eye position and a left eye position of a viewer; and generating a composite image that includes a combination of the 2D image located in the 2D display area and the 3D image located in the 3D display area as a result of the performing of all the 2D rendering operations and the performing of all the 3D rendering operations.