3d building generalization for digital map applications

Abstract

A digital map application enables display of a large amount of 3D buildings or 3D structures to provide enhanced display and navigation features. The 3D models ( 116, 216, 316 ) are composed from a detailed set of attributes which, when combined, portray a highly detailed visual rendering of a physical object as it exists in real life. By selectively suppressing attributes, and in appropriate cases deriving new attributes from existing data, varying degrees of the 3D model ( 116, 216 ) can be represented in lower levels of detail with reduced processing resources and to achieve a more realistic depiction. The generalization of the 3D models can be structured as a function of the distance between the 3D model and an imaginary observer datum or other suitable reference point. In one embodiment, a plurality of contemporaneous rendering zones ( 34, 36, 38 ) are established so that a 3D model ( 116, 216, 316 ) is displayed with a particular combination or set of attributes depending which rendering zone ( 34, 36, 38 ) it is in.

1 . A method for rendering three-dimensional (3D) objects on a display screen ( 12 ) for digital mapping applications, said method comprising the steps of:
 providing a digital map having at least one 3D model corresponding to a physical object in reality;   providing a navigation device ( 10 ) having a display screen ( 12 ) and being configured to display rendered images of the 3D model;   associating a plurality of attributes with the 3D model which, when combined, portray on the display screen ( 12 ) a detailed visual rendering of the physical object as it exists in real life;   establishing a reference point in the digital map;   selectively displaying the 3D model in the display screen ( 12 ) with different attributes depending upon the distance between the 3D model and the reference point.   
     
     
         2 . A method for rendering three-dimensional (3D) objects on a display screen ( 12 ) for digital mapping applications, said method comprising the steps of:
 providing a digital map having at least first and second 3D models corresponding to two different physical objects in reality;   associating a detailed set of attributes with the first 3D model which, when combined, portray a detailed visual rendering of the corresponding physical object as it exists in real life;   associating a detailed set of attributes with the second 3D model which, when combined, portray a detailed visual rendering of the corresponding physical object as it exists in real life;   providing a navigation system having a display screen ( 12 ) capable of presenting a portion of the digital map including the first and second 3D models;   establishing a reference point in the digital map, the first 3D model being spatially closer to the reference point than the second 3D model; and   displaying the first 3D model with substantially all of its detailed set of attributes while simultaneously displaying the second 3D model with a modified set of attributes generalized from its detailed set of attributes.   
     
     
         3 . A method for rendering three-dimensional (3D) objects on a display screen ( 12 ) for digital mapping applications, said method comprising the steps of:
 providing a navigation system having a display screen ( 12 );   providing a digital map having at least one 3D model corresponding to a physical object in reality;   associating a plurality of attributes with the 3D model which, when combined, portray on the display screen ( 12 ) a detailed visual rendering of the physical object as it exists in real life;   establishing a plurality of contemporaneous rendering zones in the digital map as viewed in the display screen ( 12 ), the contemporaneous rendering zones including a proximal rendering zone ( 34 ,  34 ′) and a distal rendering zone ( 38 ,  38 ′); and   selectively displaying the 3D model in the display screen ( 12 ) with different attributes depending upon which rendering zone the 3D model is in, wherein the 3D model is displayed with the most detailed attributes when located in the proximal rendering zone ( 34 ,  34 ′) and with generalized attributes when located in the distal rendering zone ( 38 ,  38 ′).   
     
     
         4 . The method according to  claim 1  including establishing an intermediate rendering zone spaced between the proximal and distal rendering zones, and when the 3D model is in the intermediate rendering zone displaying the 3D model on the display screen ( 12 ) with more generalized attributes than when located in the proximal rendering zone and less generalized attributes than when located in the distal rendering zone. 
     
     
         5 . The method according to  claim 1 , further including establishing a reference point in relation to the digital map, the proximal rendering zone disposed adjacent the reference point and the distal rendering zone spaced farthest from the reference point. 
     
     
         6 . The method according to  claim 1 , wherein said step of establishing a plurality of rendering zones includes arranging the rendering zones generally parallel to the road centerline. 
     
     
         7 . The method according to  claim 1 , further including the step of rendering at least two adjacent 3D models as a single building group at a lower level of detail setting. 
     
     
         8 . The method according to  claim 1 , wherein the attributes of the 3D model include object shape, roof shape, average color, and façade detail. 
     
     
         9 . The method according to  claim 1 , further including the step of deriving an average façade color attribute from a façade texture attribute. 
     
     
         10 . The method according to  claim 1 , further including the step of deriving an average roof color attribute from a roof texture attribute. 
     
     
         11 . The method according to  claim 1  further including the step of moving the 3D model relative to the reference point in the screen, and changing the attributes displayed with the 3D model if the 3D model moves to a different rendering zone. 
     
     
         12 . The method according to  claim 1 , wherein said step of establishing a reference point includes designating a centerline of the road segment as the reference point. 
     
     
         13 . A navigation-capable device ( 10 ) configured to display a driving route on the display screen ( 12 ) according to  claim 1 . 
     
     
         14 . A storage medium used to store 3D model attributes for augmenting a digital map according to  claim 1 .