The first uses latitude-longitude panoramic format, also known as an equirectangular mapping. This is the same format that I use for HDR environment maps in Photorealizer, and my sky renderer already saves images to EXR (in addition to PNG), so I will be able to use my sky renderer renders as HDR environment maps for my Photorealizer renders. Plus, I have HDR environment map importance sampling in Photorealizer, so I can leave the tiny, bright, influential sun in the sky images and Photorealizer will automatically know to heavily sample the sun.
Equirectangular projection. |
The second new camera uses an angular fisheye projection. This is a pretty intuitive way to view the entire sky (and part of the ground in my implementation). This kind of picture can be captured in real life in a single shot with a fisheye lens. Real fisheye lenses are pretty advanced. Here is a site that shows how a real fisheye lens works, with nice diagrams of the fancy optics.
Angular fisheye projection. |
The environment is identical in both images above. The solar elevation angle is 10°. I think that the two bright peaks above the horizon in the solar and anti-solar directions are due to the forward and backward peaks of the Rayleigh scattering phase function.
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