skyModel

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This is a MATLAB implementation of the Perez sky model [1] that we've re-parameterized as a function of common camera parameters, as explained in our IJCV 2010 paper [2].

See the following website for more information:

http://graphics.cs.cmu.edu/projects/sky/

=== TEST FILE ===

Use the file 'synthesizeSky.m' as a starting point.

=== SKY MODEL ===

These files synthesize the sky model based on camera parameters as inputs:

• exactSkyModel.m: Synthesizes the full sky model;
• exactGradientModel.m: Synthesizes only the "gradient" part of the sky model;
• exactSunModel.m: Synthesizes only the "sun" part of the sky model.

These files synthesize the sky model based on angles as inputs (Perez sky model):

• perezSkyModel.m: Synthesizes the full sky model;
• perezGradientModel.m: Synthesizes only the "gradient" part of the sky model;
• perezSunModel.m: Synthesizes only the "sun" part of the sky model.

Useful files that convert from pixel coordinates to angles:

• pixelAzimuthAngle.m: Converts from pixels to azimuth angle;
• pixelZenithAngle.m: Converts from pixels to zenith angle.

=== TURBIDITY ===

These files deal with converting the turbidity to the Perez weather coefficients (in 3 channels in xyY color space, as in [3]):

• convertTurbidityToSkyParams.m: Converts turbidity to the weather coefficients;
• getTurbidityMapping.m: Returns the turbidity mapping between the weather coefficients in each channel.

=== REFERENCES ===

[1] R. Perez, R. Seals, and J. Michalsky, "All-weather model for sky luminance distribution -- preliminary configuration and validation," Solar Energy, vol. 50, no. 3, pp. 235--245, Mar. 1993.

[2] J.-F. Lalonde, S. G. Narasimhan, and A. A. Efros, "What do the sun and the sky tell us about the camera?," International Journal of Computer Vision, vol. 88, no. 1, pp. 24--51, May 2010.

[3] A. J. Preetham, P. Shirley, and B. Smits, "A practical analytic model for daylight," presented at the Proceedings of ACM SIGGRAPH 1999, 1999.

=== CHANGELOG ===

09/18/12: Now using github! See commit messages for changelogs. 09/21/11: Added missing file 'exactGradientModelRatio.m'. Thanks to A. Ravichandran for pointing this out!