lighting_and_shading - CAP4730 Computational Structures in...

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CAP4730: Computational Structures in Computer Graphics Lighting and Shading
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Outline Lighting Lighting models Ambient Diffuse Specular Surface Rendering Methods Ray-Tracing
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What we know We already know how to render the world from a viewpoint.
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“Lighting” Two components: Lighting Model or Shading Model - how we calculate the intensity at a point on the surface Surface Rendering Method - How we calculate the intensity at each pixel
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Jargon Illumination - the transport of light from a source to a point via direct and indirect paths Lighting - computing the luminous intensity for a specified 3D point, given a viewpoint Shading - assigning colors to pixels Illumination Models: Empirical - approximations to observed light properties Physically based - applying physics properties of light and its interactions with matter
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The lighting problem… What are we trying to solve? Global illumination – the transport of light within a scene. What factors play a part in how an object is “lit”? Let’s examine different items here…
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Two components Light Source Properties Color (Wavelength(s) of light) Shape Direction Object Properties Material Geometry Absorption
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Light Source Properties Color We usually assume the light has one wavelength Shape point light source - approximate the light source as a 3D point in space. Light rays emanate in all directions. good for small light sources (compared to the scene) far away light sources
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Distributed Lights Light Source Shape continued distributed light source - approximating the light source as a 3D object. Light rays usually emanate in specific directions good for larger light sources area light sources
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Light Source Direction In computer graphics, we usually treat lights as rays emanating from a source. The direction of these rays can either be: Omni-directional (point light source) Directional (spotlights)
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Light Position We can specify the position of a light one of two ways, with an x , y , and z coordinate. What are some examples? These lights are called positional lights Q: Are there types of lights that we can simplify? A: Yep! Think about the sun. If a light is significantly far away, we can represent the light with only a direction vector. These are called directional lights. How does this help?
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Contributions from lights We will breakdown what a light does to an object into three different components. This APPROXIMATES what a light does. To actually compute the rays is too expensive to do in real-time.
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