lec8 - Lighting Models Computer Graphics Lecture 8 Contents...

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Lighting Models Computer Graphics Lecture 8
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Contents What is Lighting Light sources Ilumination models Ambient ( יתביבס רוא ) Diffuse ( רזופמ רזחה ) Specular ( יאר רזחה ) Phong Specular Reflection model Phong Simplified Model Adding the intensity attenuation Summary
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Lighting model What is a lighting model? lighting model == approximation of real-world lighting! Standard lighting model consist of three components: Diffuse component for the amount of incoming light reflected equally in all directions Specular component for the amount of light reflected in a mirror-like fashion Ambient term to approximate light arriving via other surfaces + +
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Lighting Sources Two basic groups of lighting sources available Light-emitting sources Example: the sun, light bulb Light-reflecting sources Example: room walls, mirror, etc…
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Light Sources (cont’) Two aspects of light sources are important for a local shading model: Where is the light coming from (the L vector)? How much light is coming (the I values)? Various light source types give different answers to the above questions: Directional: Light from a specific direction (neon light, sun light) Point light source: Light from a specific point Spotlight: Light from a specific point with intensity that depends on the direction
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Directional Light When light is coming from a distant source light rays are parallel light ray direction is the same everywhere in the scene as if the source were infinitely far away good approximation to sunlight Specified by a unit length direction vector, and a color I src L n d I l src l I I d L
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Point Lights For closer light sources, such as light bulbs Model as a point that radiates light in all directions equally Light vector varies across the surface Intensity from a point light source drops off proportionally to the inverse square of the distance from the light I l v p I src L n n L I l v 2 v p I I v p v p L src l
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Spotlights Like point source, but intensity depends on direction: Position: the location of the source Spot direction: the center axis of the light Requires falloff parameters: how broad the beam is (cone angle) how light tapers off at edges of he beam (cosine exponent) I src L n d I l p otherwise d L I d L if I v p v p L f src l ) ( ) cos( 0 max v
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This note was uploaded on 04/14/2011 for the course CS 61118 taught by Professor Alexfrid during the Fall '11 term at Technion.

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lec8 - Lighting Models Computer Graphics Lecture 8 Contents...

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