COMPUTER SYSTEM AND METHOD FOR GENERATING A 3D GEOMETRIC MODEL

• US 20100214291A1
• Filed: 07/22/2008
• Published: 08/26/2010
• Est. Priority Date: 07/27/2007
• Status: Active Grant

• Current Assignee: PROCEDURAL AG
• Original Assignee: ETH Zurich
• Inventors: Zeng, Gang, Van Gool, Luc, Müller, Pascal
• Granted Patent: US 8,970,579 B2
• Time in Patent Office: Days
• US Class Current: 345/420
• CPC Class Codes: G06F 30/13 Architectural design, e.g. computer-aided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads
• CPC Class Codes: G06T 17/005 Tree description, e.g. octree, quadtree
• CPC Class Codes: G06T 17/10 Constructive solid geometry [CSG] using solid primitives, e.g. cylinders, cubes
• CPC Class Codes: G06V 10/44 Local feature extraction by analysis of parts of the pattern, e.g. by detecting edges, contours, loops, corners, strokes or intersections; Connectivity analysis, e.g. of connected components

Abstract

For generating a 3D geometric model (44) and/or a definition of the 3D geometric model from a single digital image of a building facade (4), a facade structure is detected from the digital image by dividing the facade (4) along horizontal lines into horizontal layers representative of floors (41), and by dividing the horizontal layers along vertical lines into tiles (42). The tiles (42) are further subdivided into a hierarchy of rectangular image regions (43). 3D architectural objects (45) corresponding to the image regions (43) are determined in an architectural element library. The 3D geometric model (44) or the definition of the 3D geometric model is generated based on the facade structure, the hierarchy and the 3D architectural objects (45). The library-based generation of the 3D geometric model makes it possible to enhance simple textured building models constructed from aerial images and/or ground-based photographs.

Claims

1. A system for generating a 3D (three dimensional) geometric model and/or a definition of the 3D geometric model from a digital image of a building facade, the system comprising:

a computer system comprising one or more processors, said computer system programmed to implement at least;

a structure detector configured to subdivide the digital image into image regions;

an architectural element library comprising 3D architectural objects;

an element detector configured to determine in the architectural element library 3D architectural objects corresponding to the image regions; and

a generator configured to generate the 3D geometric model or the definition of the 3D geometric model based on the 3D architectural objects determined.

2. The system of claim 1, wherein the structure detector is configured to detect a facade structure from the digital image by dividing the facade along horizontal lines into horizontal layers representative of floors, and by dividing the horizontal layers along vertical lines into tiles representative in each case of an architectural building element and its surrounding wall, and to subdivide the tiles into a hierarchy of rectangular image regions;

and

the generator is configured to generate the 3D geometric model or the definition of the 3D geometric model based on the facade structure, the hierarchy and the 3D architectural objects.

3. The system of claim 1, wherein the structure detector is configured to determine similar horizontal layers by detecting vertical symmetry in a vertical direction, to determine similar vertical columns by detecting horizontal symmetry in a horizontal direction, to generate an irreducible facade structure with horizontal layers reduced to non-similar horizontal layers by stacking up the similar horizontal layers, and with columns reduced to non-similar columns by stacking up the similar columns, and to determine in the irreducible facade structure horizontal splitting lines which divide the facade into floors, and vertical splitting lines which divide the facade into tiles.

4. The system of claim 3, wherein the structure detector is configured to subdivide the tiles into the hierarchy of rectangular image regions by aligning horizontal splits within horizontal rows of tiles, and aligning vertical splits within vertical columns of tiles, based on information about horizontal and vertical repetition of similar tiles included in the irreducible facade structure.

5. The system of claim 1, wherein the element detector is configured to determine the 3D architectural objects by determining a 2D representation of the 3D architectural objects included in the architectural element library, determining clusters of similar image regions, and determining in each case the 2D representation having a best match with the image regions of a cluster.

6. The system of claim 1, wherein the generator is further configured to generate the 3D geometric model or the definition of the 3D geometric model based on shader information associated with the 3D architectural objects.

7. A computer-implemented method of generating a 3D geometric model and/or a definition of the 3D geometric model from a digital image of a building facade, the method comprising:

subdividing the digital image into image regions;

determining in an architectural element library 3D architectural objects corresponding to the image regions; and

generating the 3D geometric model or the definition of the 3D geometric model based on the 3D architectural objects determined.

8. The method of claim 7, wherein subdividing the digital image into image regions comprises detecting a facade structure from the digital image by dividing the facade along horizontal lines into horizontal layers representative of floors, and by dividing the horizontal layers along vertical lines into tiles representative in each case of an architectural building element and its surrounding wall, and subdividing the tiles into a hierarchy of rectangular image regions;

and generating the 3D geometric model or the definition of the 3D geometric model based on the facade structure, the hierarchy and the 3D architectural objects.

9. The method of claim 8, wherein detecting the facade structure further comprises determining similar horizontal layers by detecting vertical symmetry in a vertical direction, determining similar vertical columns by detecting horizontal symmetry in a horizontal direction, generating an irreducible facade structure with horizontal layers reduced to non-similar horizontal layers by stacking up the similar horizontal layers, and with columns reduced to non-similar columns by stacking up the similar columns, and determining in the irreducible facade structure horizontal splitting lines which divide the facade into the floors, and vertical splitting lines which divide the facade into the tiles.

10. The method of claim 9, wherein subdividing the tiles into the hierarchy of rectangular image regions includes aligning horizontal splits within horizontal rows of tiles, and aligning vertical splits within vertical columns of tiles, based on information about horizontal and vertical repetition of similar tiles included in the irreducible facade structure.

11. The method of claim 7, wherein determining the 3D architectural objects comprises determining a 2D representation of the 3D architectural objects included in the architectural element library, determining clusters of similar image regions, and determining in each case the 2D representation having a best match with the image regions of a cluster.

12. The method of claim 7, wherein generating the 3D geometric model or the definition of the 3D geometric model is further based on shader information associated with the 3D architectural objects.

13. A computer program product comprising a computer readable medium having stored thereon computer program code which directs a computer system to:

subdivide a digital image of a building facade into image regions;

determine in an architectural element library 3D architectural objects corresponding to the image regions; and

generate a 3D geometric model and/or a definition of the 3D geometric model based on the 3D architectural objects determined.

14. The computer program product of claim 13 wherein the computer program code additionally directs the computer system to:

detect a facade structure from the digital image by dividing the facade along horizontal lines into horizontal layers representative of floors, and by dividing the horizontal layers along vertical lines into tiles representative in each case of an architectural building element and its surrounding wall;

subdivides the tiles into a hierarchy of rectangular image regions; and

generates the 3D geometric model or the definition of the 3D geometric model based on the facade structure, the hierarchy and the 3D architectural objects.

15. Physical computer storage having stored therein:

a data structure defining a 3D geometric model of a building facade for a computerized graphics generator, the data structure comprising;

a first data element indicating information about an order of floors and a number of repetitions of a respective floor, a floor being representative of a horizontal layer of the building facade;

one or more second data elements indicating in each case for one of the floors an order of tiles and a number of repetitions of a respective tile, a tile being representative of a segment of a floor with the full height of the floor;

one or more third data elements indicating in each case for one of the tiles a partial region of the respective tile; and

one or more fourth data elements indicating in each case for one of the partial regions a 3D architectural object for rendering by the computerized graphics generator; and

executable instructions that direct a computer system to manipulate the data structure.