Texture mapping system used for creating three-dimensional urban models

• US 6,744,442 B1
• Filed: 08/29/2000
• Issued: 06/01/2004
• Est. Priority Date: 08/29/2000
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Nemethy, Joseph M., Rahmes, Mark D., Boss, Mark E., Chan, Ellery Y.
• Primary Examiner(s): Razavi, Michael
• Assistant Examiner(s): GOOD JOHNSON, MOTILEWA
• Application Number:
  US09/652,118
• Time in Patent Office: 1,372 Days
• Field of Search: 345/582, 345/426
• US Class Current: 345/587
• CPC Class Codes: G06T 15/04 Texture mapping

Abstract

A method and system are disclosed for creating three-dimensional models in a graphics texture mapping system and are especially useful for creating three-dimensional urban models. A computer includes a graphics application program and an application programming interface. A single rectangular, composite building texture map is formed for each of a plurality of three-dimensional objects corresponding to individual buildings and have a reduced area of pixels within each composite building texture map as caused by rotating individual images. A site model clip map image contains each composite building texture map in a spatially correct position that has been expanded such that no overlap remains.

Claims

1. A method for creating textured three-dimensional models in a computer system comprising the steps of:

creating a packed rectangle of textures for each of a plurality of three-dimensional objects corresponding to buildings modeled at a geographic site;

spatially arranging the packed rectangle of textures in a correct position with a site model clip map image;

interrogating the vertices of all building polygon faces for their corresponding texture coordinates and inserting the coordinates into a clip map clip grid look-up table based on the polygon vertex coordinates;

determining a location of a clip center with respect to a particular x,y location for the site model clip map image by looking up values within the clip map clip grid look-up table; and

looking up a values within a second look-up table to compensate for locally limitations introduced into the site model clip map image and for spatial incoherence within the site model clip map image.

2. A method according to claim 1, and further comprising the steps of:

collecting images of each of the plurality of three-dimensional objects from different viewpoints; and

packing the images into a single rectangle, forming a composite building texture map for an object.

3. A method according to claim 2, and further comprising the step of rotating individual images to reduce the area of pixels included within the composite building texture map.

4. A method according to claim 2, and further comprising the step of calculating an image size having the smallest area with the smallest perimeter containing all the individual textures for each of the three-dimensional objects.

5. A method according to claim 2, and further comprising the step of checking each composite building texture map for overlap against other composite building texture map within the site model clip map image and expanding same until no overlap exists.

6. A method according to claim 1, and further comprising the step of building the clip map clip grid look-up table by interrogating the vertices of all building polygon faces for corresponding texture coordinates and inserting each texture coordinate into the look-up table based on the corresponding polygon face vertex coordinate.

7. A method according to claim 6, and further comprising the step of building the clip map clip grid look-up table indices using an x,y camera location.

8. A method according to claim 6, and further comprising the step of introducing a scale factor to normalize x,y scene location for the site model clip map image when a clip map corresponding to a geographic terrain and the site model clip map image are different sizes.

9. A method for creating textured three-dimensional models in a computer system comprising the steps of:

forming a single rectangular, composite building texture map for each of a plurality of three-dimensional objects corresponding to buildings modeled at a geographic site;

rotating individual images of the three-dimensional objects to reduce the area of pixels included within the composite building texture map;

processing image sizes by area and image length and sorting same by area and image length;

placing each composite building texture map in a spatially correct position within a site model clip map image;

expanding the site model clip map image until no overlap remains;

interrogating the vertices of all building polygon faces for their corresponding texture coordinate and inserting the coordinates into a clip map clip grid look-up table based on the polygon face vertex coordinates;

determining a location of a clip center with respect to a particular x,y location for the site model clip map image by looking up values within the clip map clip grid look-up table; and

looking up values within a second look-up table to compensate for locality limitations introduced into the site model clip map image and for spatial incoherence within the site model clip map image.

10. A method according to claim 9, and further comprising the step of expanding the site model clip map image from one direction to another.

11. A method according to claim 9, and further comprising the step of building the clip map clip grid look-up table by interrogating the vertices of all building polygon faces for corresponding texture coordinates and inserting each texture coordinate into the look-up table based on the corresponding polygon face vertex coordinate.

12. A system for creating three-dimensional models in a computer system and applicable for creating three-dimensional urban models and comprising:

a computer, including a graphics application program and an application programming interface;

a single rectangular, composite building texture map for each of a plurality of three-dimensional objects corresponding to individual buildings and having a reduced area of pixels within each composite building texture map as caused by rotating individual images;

a site model clip map image containing each composite building texture map in a spatially correct position and that has been expanded such that no overlap remains;

a clip map clip grid look-up table used for determining a location of a clip center with respect to a particular x,y location for the site model clip map image, said clip map clip grid look-up table formed as data representing vertices of all building polygon faces as interrogated for their corresponding texture coordinates based on polygon face vertex coordinates; and

a second look-up table having values that are looked-up to compensate for locality limitations introduced into the site model clip map image and for spatial incoherence within the site model clip map image.