Systems and methods for the real-time and realistic simulation of natural atmospheric lighting phenomenon

Abstract

Systems and methods are provided for visually realistic simulation and real-time rendering of natural atmospheric lighting and related phenomena in an outdoor scene represented by an image provided by a simulation environment. The systems and methods of the present invention provide techniques to approximate the visual effects of natural atmospheric lighting and related phenomena that are visually realistic and that can be computed in real-time to render frames of a scene at real-time frame rates per second. The techniques consider the light scattering effects due to sunlight and ambient light in relation to objects, atmospheric particles and other scene elements represented by the image.

1 . A method for approximating a realistic color of an object based on wavelength dependent approximations of atmospheric lighting phenomenon, the method comprising:
 (a) specifying, via a simulation engine executing on a device, a first RGB constant for a Raleigh scattering component of an atmosphere to be rendered on a display of the device;   (b) specifying, via the simulation engine, a second RGB constant for a Mie scattering component of the atmosphere;   (c) calculating, by the simulation engine, for each color channel, a cumulative density of particles of the atmosphere along a ray between a viewing position of an object and the object by summing a first result of a first integral of a corresponding color channel of the first RGB constant multiplied by a length of a portion of the ray intersecting the atmosphere and a second result of a second integral of the corresponding color channel of the second RGB constant multiplied by the length of the portion of the ray intersecting the atmosphere;   (d) determining, by the simulation engine, an attenuation factor for each color channel by taking an exponential function of a negative of the cumulative density calculated for the corresponding color channel; and   (e) rendering, by the simulation engine, a color for the object from atmospheric light scattering based on each attention factor of each color channel.   
   
   
       2 . The method of  claim 1 , wherein step (a) further comprises specifying by a user, via the simulation engine, the first RGB constant. 
   
   
       3 . The method of  claim 1 , wherein step (a) further comprises specifying by a user, via the simulation engine, the second RGB constant. 
   
   
       4 . The method of  claim 1 , wherein step (a) further comprises applying a weight to one or more color channels of the first RGB constant. 
   
   
       5 . The method of  claim 1 , wherein step (b) further comprises applying a weight to one or more color channels of the second RGB constant. 
   
   
       6 . The method of  claim 1 , wherein step (d) further comprises determining, by the simulation engine, an additive term for each color channel by multiplying a convergence color by each color channel's attenuation factor subtracted from a value of one, the convergence color based on a user specified color for the Rayleigh and Mie components of the atmosphere. 
   
   
       7 . The method of  claim 6 , wherein step (e) further comprises determining the color of the object by multiplying each color channel's attenuation factor by the corresponding color channel of the object's RGB value and adding to this result the additive term for the corresponding color channel. 
   
   
       8 . The method of  claim 6 , further comprising determining, by the simulation engine, the convergence color by taking a weighted average of a user specified Rayleigh convergence color component and a user specified Mie convergence color component. 
   
   
       9 . The method of  claim 1 , further comprising determining, by the simulation engine, the convergence color by taking a weighted average of a Rayleigh convergence color component and a Mie convergence color component according to relative densities of the Rayleigh convergence color component and thes Mie convergence color component. 
   
   
       10 . A method for approximating a realistic appearance of clouds using a plurality of cloud textures with independent weightings, the method comprising:
 (a) obtaining, by a simulation engine executing on a device, a plurality of cloud textures to represent a cloud to be rendered on a display of the device, each of the plurality of cloud textures having a weighting attribute;   (b) determining, by the simulation engine, a density of the cloud from an aggregate of cloud density values at each texture coordinate of each cloud texture weighted by the weighting attribute; and   (c) rendering, by the simulation engine, the cloud on the display based on the determined density of the cloud.   
   
   
       11 . The method of  claim 10 , wherein step (b) further comprises adding an offset value to the aggregate of the cloud density values. 
   
   
       12 . The method of  claim 11 , wherein the offset value is adjustable by a user. 
   
   
       13 . The method of  claim 11 , further comprising determining the offset value by applying a constant to a sum of the weighting attribute values. 
   
   
       14 . The method of  claim 10 , wherein the cloud density value at a texture coordinate and a weighting attribute of a first cloud texture is independent from a cloud density value at a texture coordinate and a weighting attribute of a second cloud texture. 
   
   
       15 . The method of  claim 10 , wherein tiling, by the simulation engine, the plurality of cloud textures to represent the cloud. 
   
   
       16 . The method of  claim 10 , further comprising using, by the simulation engine, the determination of the density of the cloud from step (b) to determine an opacity of the cloud. 
   
   
       17 . The method of  claim 10 , further comprising determining, by the simulation engine, an opacity of the cloud by taking an exponential function of a negative of the density of the cloud. 
   
   
       18 . The method of  claim 17 , further comprising subtracting a result of the exponential function of a negative of the density of the cloud from a value of one to determine the opacity. 
   
   
       19 . The method of  claim 10 , further comprising obtaining, by the simulation engine, a cloud opacity offset. 
   
   
       20 . The method of  claim 19 , further comprising determining, by the simulating engine, the opacity by dividing the density of the could by the cloud opacity offset and subtracting from a value of one and taking this result and raising by a power of the cloud opacity offset.