Blending 3D model textures by image projection

1. A method, performed on one or more processors, for blending textures of a composite image formed by a plurality of source images mapped onto a three dimensional model, comprising:

projecting the composite image to obtain a two dimensional, unblended, projected image having textures;

blending the textures of the unblended projected image to obtain a blended projected image;

backprojecting the unblended projected image and the blended projected image onto the three dimensional model;

determining a difference between a pixel of the backprojected, blended image and a corresponding pixel of the backprojected, unblended image; and

applying the determined difference to a further corresponding pixel of the composite image to obtain a modified composite image representing a blending of the plurality of source images in the composite image.

2. The method of claim 1 , wherein the projecting comprises projecting an oblique composite image.

3. The method of claim 1 , wherein the projecting comprises orthorectifying the composite image to obtain an unblended orthorectified image.

4. The method of claim 1 , wherein the blending comprises blending the textures using a multiband blending technique.

5. The method of claim 1 , further comprising tagging each pixel of the composite image with an ID corresponding to the source image associated with the pixel.

6. The method of claim 1 , further comprising dividing the unblended projected image into a plurality of tiles.

7. The method of claim 6 , further comprising overlapping each of the plurality of tiles in at least one of X and Y dimensions.

8. The method of claim 6 , wherein the textures within each of the plurality of tiles are blended individually.

9. The method of claim 8 , wherein the blending the textures comprises blending each of the plurality of tiles together to obtain the blended projected image.

10. The method of claim 1 , wherein the determining a difference comprises determining an additive change between a pixel of the backprojected, blended image and a corresponding pixel of the backprojected, unblended image.

11. The method of claim 1 , wherein the determining a difference comprises determining a multiplicative change between a pixel of the backprojected, blended image and a corresponding pixel of the backprojected, unblended image.

12. A system for blending textures of a composite image formed by a plurality of source images mapped onto a three dimensional model, comprising:

an image projector configured to project the composite image to obtain a two dimensional, unblended projected image having textures;

a blending engine configured to blend the textures of the unblended projected image to obtain a blended projected image;

a backprojecting engine configured to backproject the unblended projected image and the blended projected image onto the three dimensional model; and

a pixel processing unit configured to:

determine a difference between a pixel of the backprojected, blended image and a corresponding pixel of the backprojected, unblended image, and

apply the difference to a further corresponding pixel of the composite image to obtain a modified composite image representing a blending of the plurality of source images in the composite image.

13. The system of claim 12 , wherein the image projector is configured to orthorectify the composite image to obtain an unblended orthorectified image.

14. The system of claim 12 , wherein the plurality of source images illustrate content of the model at different perspectives.

15. The system of claim 12 , wherein the plurality of source images illustrate content of the model at various brightness levels.

16. The system of claim 12 , wherein the plurality of source images illustrate content of the model at various exposure settings.

17. The system of claim 12 , wherein the blending engine is configured to blend the textures using a multiband blending technique.

18. The system of claim 12 , wherein the composite image is derived from a digital surface model (DSM).

19. The system of claim 12 , wherein the blending engine is further configured to separately blend tiled regions of the unblended projected image.

20. An apparatus comprising at least one non-transitory computer readable storage medium encoding instructions thereon that, in response to execution by a computing device, cause the computing device to perform operations comprising:

projecting the composite image formed by a plurality of the source images mapped onto a three dimensional model to obtain a two dimensional, unblended projected image having textures;

blending the textures of the unblended projected image to obtain a blended projected image;

backprojecting the unblended projected image and the blended projected image onto the three dimensional model;

determining a difference between a pixel of the backprojected, blended image and a corresponding pixel of the backprojected, unblended image; and

applying the determined difference to a further corresponding pixel of the composite image to obtain a modified composite image representing a blending of the plurality of source images in the composite image.

21. The apparatus of claim 20 , wherein the plurality of source images illustrate content of the model at different perspectives.

22. The apparatus of claim 20 , wherein the plurality of source images illustrate content of the model at various brightness levels.

23. The apparatus of claim 20 , wherein the plurality of source images illustrate content of the model at various exposure settings.

24. The apparatus of claim 20 , wherein the composite image is derived from a digital surface model (DSM).