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This paper presents an interactive shading model for capturing volumetric light attenuation effects, allowing for the realistic modeling of high-frequency detail in volumetric data. The technique also incorporates sub-surface scattering effects, color bleeding, and diffusion of light across boundaries. The implementation includes dynamic parameters, such as light direction and volume data, and utilizes random walk modeling for multiple scattering.
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Paper-4 Interactive Translucent Volume Rendering and Procedural Modeling Joe Kniss Simon Premoze Charles HansenDavid Ebert Univ of Utah
Introduction • Interactive shading model which captures volumetric light attenuation effects to produce volumetric shadows and the qualitative appearance of translucency. • A technique for volume displacement or perturbation that allows realistic interactive modeling of high frequency detail for real and synthetic volumetric data. • Appearance of many common objects dominated by sub surface scattering effects • Need not be accurate but interactive
Volume shading model • Multiple scattering and indirect illumination effects are important and no restrictions on external illumination and optical properties • Color bleeding and diffusion of light across boundaries are also consequences of multiple scattering • Full global illumination , backward scattering and volumetric light sources not part of this model
Model • Translucency implies blurring of light thro the medium • Multiple scattering modeled as random walk->light is diffused within volume • Surface shading parameter set automatically using gradient magnitude at the sample
Implementation • Tf , light direction and volume data not static. • Diffuse reflectance material , absorption/emission , shadows , indirect attenuation term • Transport color- the color indirect light becomes after getting attenuated by the material
Rendering • Uses half angle slicing • modification of the slicing axis allows us to render each slice from the point of view of both the observer and the light. • Total of 3 image buffers • Two buffers are maintained for the attenuation of light in the light direction (current and next), • One buffer for the accumulation of light for the observer, which is typically the frame buffer • Ping-pong blending current next.
