Specularity

<h2 id="in-computer-graphics">In computer graphics</h2>
<p>In <a href="/facts/Computer_graphics/lapBE8wv">computer graphics</a>, it means the quantity used in three-dimensional (3D) <a href="/facts/Rendering_(computer_graphics)/YYxfnmAq">rendering</a> which represents the amount of <a href="/facts/Reflection_coefficient/se689p3C">reflectivity</a> a surface has. It is a key component in determining the <a href="/facts/Brightness/e93R5I4b">brightness</a> of <a href="/facts/Specular_highlights/4VI6wGGx">specular highlights</a>, along with shininess to determine the size of the <a href="/facts/Specular_highlight/4VI6wGGx">highlights</a>.
</p><p>It is frequently used in <a href="/facts/Real-time_computer_graphics/jrILnb0K">real-time computer graphics</a> and <a href="/facts/Ray_tracing_(graphics)/n6qpap2q">ray tracing</a>, where the mirror-like specular reflection of <a href="/facts/Light/jeofpMn4">light</a> from other surfaces is often ignored (due to the more intensive computations required to calculate it), and the specular reflection of light directly from point light sources is modeled as specular highlights.
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<h3>Specular mapping</h3>
<p>A <a href="/facts/Materials_system/zlWW6eaF">materials system</a> may allow specularity to vary across a surface, controlled by additional layers of <a href="/facts/Texture_maps/9gDTsuXN">texture maps</a>.
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<h3>The early misinterpretation of "Specularity" in computer graphics</h3>
<p>Early shaders included a parameter called "Specularity". CG Artists, confused by this term discovered by experimentation that the manipulation of this parameter would cause a reflected highlight from a light source to appear and disappear and therefore misinterpreted "specularity" to mean "light highlights". In fact "Specular" is defined in optics as <i>Optics. (of reflected light) directed, as from a smooth, polished surface (opposed to <a href="/facts/Diffuse_reflection/wG9w4tAX">diffuse</a> ).</i> A specular surface is a highly smooth surface.  When the surface is very smooth, the reflected highlight is easy to see.  As the surface becomes rougher, the reflected highlights gets broader and dimmer.  This is a more "diffused" reflection.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a><a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
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<h2 id="in-seismology">In seismology</h2>
<p>In the context of <a href="/facts/Seismic_migration/yqd1EI3e">seismic migration</a>, specularity is defined as the cosine of the angle made by the <a href="/facts/Surface_normal/jhtLIhcu">surface normal</a> vector and the <a href="/facts/Angle_bisector/JTsya7Ca">angle bisector</a> of the angle defined by the directions of the incident and diffracted rays.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> For a purely specular seismic event the value of specularity should be equal to unity, as the angle between the surface normal vector and the angle bisector should be zero, according to Snell's Law. For a diffractive seismic event, the specularity can be sub-unitary. During the seismic migration, one can filter each seismic event according to the value of specularity, in order to enhance the contribution of <a href="/facts/Diffraction/Mk80xXHT">diffractions</a> in the seismic image. Alternatively, the events can be separated in different sub-images according to the value of specularity to produce a <a href="/facts/Specularity_gather/KAUEvtnd">specularity gather</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
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<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Specular_holography/r43wRfS0">Specular holography</a></li>
<li><a href="/facts/Reflection_mapping/oPL8X8Br">Reflection mapping</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"Definition of specular | Dictionary.com". www.dictionary.com. Retrieved 25 July 2021. <a href="http://www.dictionary.com/browse/specular" target="_blank">http://www.dictionary.com/browse/specular</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"Physics Tutorial: Specular vs. Diffuse Reflection". www.physicsclassroom.com. Retrieved 25 July 2021. <a href="http://www.physicsclassroom.com/class/refln/Lesson-1/Specular-vs-Diffuse-Reflection" target="_blank">http://www.physicsclassroom.com/class/refln/Lesson-1/Specular-vs-Diffuse-Reflection</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Moser, T.J.; Howard, C.B. (2008). "Diffraction imaging in depth". Geophysical Prospecting. 56 (5): 627–641. doi:10.1111/j.1365-2478.2007.00718.x. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Sturzu, I.; et al. (2013). "Specularity Gathers for Diffraction Imaging". 75th EAGE Conference & Exhibition Incorporating SPE EUROPEC. London 2013, 75th eage conference en exhibition incorporating SPE Europec. doi:10.3997/2214-4609.20130700. ISBN 978-90-73834-48-4. <a href="978-90-73834-48-4" target="_blank">978-90-73834-48-4</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
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Specularity open-in-new

Specularity