Goal:

Explore methods of rendering scenes containing fog or cloud-like effects through a variety of different techniques.

Atmospheric effects make rendered scenes:

• become more natural and realistic
• create a better sense of depth
• impact the viewer to wonder whether they are indeed seeing a photo or a rendered picture

Example Photographs:

Final Results:

Volumetric Fog:

Volumetric fog rendering can be accomplished through Volumetric Ray Casting:

• Create a three dimensional volume
• Add Perlin noise to the volume
• Shoot a ray through the volume for each visible point from the image plane
• Take samples within the volume at various points along the ray
• Shoot a ray from the sample point to the light source
• Compute how deep the point is within the fog to the light source
• Compute the color for each sample point based on the accumulated color and how much light is present
• Composite the various samples into a final color for that pixel

The Results:

Volumetric Ray Casting





Quadric Surfaces - Cones



Quadric Surfaces - Elliptic Parabolas



Light Cones



Overall Effects



USe Cases - Sky - Dynamically create weather by tweaking light color and noise constants



Use Cases - Lighthouse Scene, Crystal Ball

Pixel Fog:

Pixel fog is achieved by:

• Applying a fog factor to each pixel to determine how much of a pixel is obscured by the fog
• Calculating by linear interpolation the accumulated color and the fog color
• Apply the fog factor linearly by specifying a fog start and a fog end
• Apply the fog exponentially by specifying a fog density and then adding noise and/or a Guassian filter
• Can be applied to the complete rendered scene and not just a single geometry

The Results:

• Untouched images



• Images rendered using a linear fog factor



• Images rendered using an exponential fog factor

Interesting Attempts:

Here are some other bizarre and interesting pictures we created!

References:

General References

• A Practical Analytic Single Scattering Model for Real Time Rendering
• Rethinking Graphics and GamingCourses Because of Fast Ray Tracing

Volumetric Fog Info

• Geometric and Path Tracing Methods for Simulating Light Transport through Volumes of Water Particles
• CS348B Final Project: Rendering a Lighthouse in Fog
• Real-Time Atmospheric Events
• Real-Time Smoke Rendering Using Compensated Ray Marching
• A Model for Volume Lighting and Modeling

Pixel Fog Info

• Ocean Fog using Direct3D 10
• DirectX 9 Fog Formulas
• OpenGL:Tutorials:Tutorial Framework:Light and Fog