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Class5 - Class 5 Illumination and Shading HW4 CS580...

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Class 5 Illumination and Shading HW4 Ulrich Neumann CS580 (Computer Graphics Rendering)
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Illumination and shading Illumination (lighting) and shading models simulation of light interactions with scene light sources, geometry, propagation, interaction with surfaces, imaging process in camera
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Shading Examples Images courtesy of Watt, Watt & Watt, and Foley & van Dam
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Global versus Local Illumination 2 P 1 P Indirect Illumination Direct Illumination
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Global versus Local Illumination Global Illumination Considers indirect illumination Reflection Refraction Shadows Local Illumination Only considers direct illumination No reflection No refraction Simple shadows possible
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Global versus Local Illumination We start with simple local illumination and then extend those concepts/models to global illumination
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Radiance Radiance: Power per unit projected source area (A) perpendicular to the ray, per unit solid angle in the direction of the ray dA N the approximation holds for small A and Ω , L is the radiance ( W · m -2 · sr -1 ), Φ is the radiant flux or power ( W ), θ is the angle between the surface normal and the specified direction, A is the area of the source ( m 2 ), and Ω is the solid angle ( sr ).
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Light Source Radiant Intensity Radiant Intensity per steradian Ie(x) = power/sr (Watts/steradian) constant in vacuum at all distances Solid angle sr = surface area (a) of portion of sphere divided by r 2 , sr = a/r 2 Area of sphere surface = 4 pi r 2 sr = (4pi r 2 )/r 2 , sr = 4pi steradians over sphere - independent of radius Ie is constant for fixed solid angle (at any distance) J = We = Watt/m 2 Radiosity or Power Density falls off with square of distance
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This note was uploaded on 04/22/2010 for the course CS 580 at USC.

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Class5 - Class 5 Illumination and Shading HW4 CS580...

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