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Atmospheric light scattering: Difference between revisions
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* The skydome simulates the scattering in an optically thin atmosphere in the absence of haze layers. As such, it takes into account Rayleigh and Mie scattering with the parameters adjusted to account for the water vapour and dust distribution above the current aircraft altitude. The current skydome shader is based on [http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter16.html work by Sean O'Neil] and is described there (in case you're interested in O'Neil's article - the reason why he is able to do what he describes in ''Eliminating One Dimension'' is that for realistic rendering distances one can neglect the full curvature of earth and Taylor-expand the expressions in the curvature, his result can then be derived analytically). Extra diffuse high-altitude layers can just be 'painted' onto the skydome. | * The skydome simulates the scattering in an optically thin atmosphere in the absence of haze layers. As such, it takes into account Rayleigh and Mie scattering with the parameters adjusted to account for the water vapour and dust distribution above the current aircraft altitude. The current skydome shader is based on [http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter16.html work by Sean O'Neil] and is described there (in case you're interested in O'Neil's article - the reason why he is able to do what he describes in ''Eliminating One Dimension'' is that for realistic rendering distances one can neglect the full curvature of earth and Taylor-expand the expressions in the curvature, his result can then be derived analytically). Extra diffuse high-altitude layers can just be 'painted' onto the skydome. | ||
* Since, for an exponential decreasing atmosphere density, the scattering integrals can be solved analytically, an extra Rayleigh haze simulating sky-blue in-scattering of light is applied to the terrain before diffuse fogging, and based on the same integrals, the redshift of the terrain underneath is computed. | |||
* A ground haze layer of given thickness and ground visibility takes care of simulating ground fog banks and visibility in the lowest convection layer. This simulates diffuse scattering only needs to enter the computations of both the skydome and the terrain shaders. | * A ground haze layer of given thickness and ground visibility takes care of simulating ground fog banks and visibility in the lowest convection layer. This simulates diffuse scattering only needs to enter the computations of both the skydome and the terrain shaders. | ||