3D graphics eBook - Course Materials Repository
3D graphics eBook - Course Materials Repository 3D graphics eBook - Course Materials Repository
Specular highlight 193 Using multiple distributions If desired, different distributions (usually, using the same distribution function with different values of m or n) can be combined using a weighted average. This is useful for modelling, for example, surfaces that have small smooth and rough patches rather than uniform roughness. References [1] Richard Lyon, "Phong Shading Reformulation for Hardware Renderer Simplification", Apple Technical Report #43, Apple Computer, Inc. 1993 PDF (http:/ / dicklyon. com/ tech/ Graphics/ Phong_TR-Lyon. pdf) [2] Glassner, Andrew S. (ed). An Introduction to Ray Tracing. San Diego: Academic Press Ltd, 1989. p. 148. [3] Petr Beckmann, André Spizzichino, The scattering of electromagnetic waves from rough surfaces, Pergamon Press, 1963, 503 pp (Republished by Artech House, 1987, ISBN 9780890062388). [4] Foley et al. Computer Graphics: Principles and Practice. Menlo Park: Addison-Wesley, 1997. p. 764. [5] R. Cook and K. Torrance. "A reflectance model for computer graphics". Computer Graphics (SIGGRAPH '81 Proceedings), Vol. 15, No. 3, July 1981, pp. 301–316. [6] http:/ / radsite. lbl. gov/ radiance/ papers/ Specularity Specularity is the visual appearance of specular reflections. In computer graphics, it means the quantity used in 3D rendering which represents the amount of specular reflectivity a surface has. It is a key component in determining the brightness of specular highlights, along with shininess to determine the size of the highlights. It is frequently used in real-time computer graphics where the mirror-like specular reflection of light from other surfaces is often ignored (due to the more intensive computations required to calculate this), and the specular reflection of light direct from point light sources is modelled as specular highlights. Specular highlights on a pair of spheres.
Sphere mapping 194 Sphere mapping In computer graphics, sphere mapping (or spherical environment mapping) is a type of reflection mapping that approximates reflective surfaces by considering the environment to be an infinitely far-away spherical wall. This environment is stored as a texture depicting what a mirrored sphere would look like if it were placed into the environment, using an orthographic projection (as opposed to one with perspective). This texture contains reflective data for the entire environment, except for the spot directly behind the sphere. (For one example of such an object, see Escher's drawing Hand with Reflecting Sphere.) To use this data, the surface normal of the object, view direction from the object to the camera, and/or reflected direction from the object to the environment is used to calculate a texture coordinate to look up in the aforementioned texture map. The result appears like the environment is reflected in the surface of the object that is being rendered. Usage example In the simplest case for generating texture coordinates, suppose: • The map has been created as above, looking at the sphere along the z-axis. • The texture coordinate of the center of the map is (0,0), and the sphere's image has radius 1. • We are rendering an image in the same exact situation as the sphere, but the sphere has been replaced with a reflective object. • The image being created is orthographic, or the viewer is infinitely far away, so that the view direction does not change as one moves across the image. At texture coordinate , note that the depicted location on the sphere is (where z is ), and the normal at that location is also . However, we are given the reverse task (a normal for which we need to produce a texture map coordinate). So the texture coordinate corresponding to normal is .
- Page 147 and 148: Radiosity 142 This is sometimes kno
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- Page 157 and 158: Ray tracing 152 On June 12, 2008 In
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- Page 163 and 164: Reflection mapping 158 Cube mapping
- Page 165 and 166: Render Output unit 160 Render Outpu
- Page 167 and 168: Rendering 162 • indirect illumina
- Page 169 and 170: Rendering 164 Ray tracing Ray traci
- Page 171 and 172: Rendering 166 Academic core The imp
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- Page 187 and 188: Shadow mapping 182 Further reading
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Specular highlight 193<br />
Using multiple distributions<br />
If desired, different distributions (usually, using the same distribution function with different values of m or n) can be<br />
combined using a weighted average. This is useful for modelling, for example, surfaces that have small smooth and<br />
rough patches rather than uniform roughness.<br />
References<br />
[1] Richard Lyon, "Phong Shading Reformulation for Hardware Renderer Simplification", Apple Technical Report #43, Apple Computer, Inc.<br />
1993 PDF (http:/ / dicklyon. com/ tech/ Graphics/ Phong_TR-Lyon. pdf)<br />
[2] Glassner, Andrew S. (ed). An Introduction to Ray Tracing. San Diego: Academic Press Ltd, 1989. p. 148.<br />
[3] Petr Beckmann, André Spizzichino, The scattering of electromagnetic waves from rough surfaces, Pergamon Press, 1963, 503 pp<br />
(Republished by Artech House, 1987, ISBN 9780890062388).<br />
[4] Foley et al. Computer Graphics: Principles and Practice. Menlo Park: Addison-Wesley, 1997. p. 764.<br />
[5] R. Cook and K. Torrance. "A reflectance model for computer <strong>graphics</strong>". Computer Graphics (SIGGRAPH '81 Proceedings), Vol. 15, No. 3,<br />
July 1981, pp. 301–316.<br />
[6] http:/ / radsite. lbl. gov/ radiance/ papers/<br />
Specularity<br />
Specularity is the visual appearance of specular reflections. In<br />
computer <strong>graphics</strong>, it means the quantity used in <strong>3D</strong> rendering which<br />
represents the amount of specular reflectivity a surface has. It is a key<br />
component in determining the brightness of specular highlights, along<br />
with shininess to determine the size of the highlights.<br />
It is frequently used in real-time computer <strong>graphics</strong> where the<br />
mirror-like specular reflection of light from other surfaces is often<br />
ignored (due to the more intensive computations required to calculate<br />
this), and the specular reflection of light direct from point light sources<br />
is modelled as specular highlights.<br />
Specular highlights on a pair of spheres.
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