光学相关定义和公式
<p><a href="https://zhuanlan.zhihu.com/p/139468429">https://zhuanlan.zhihu.com/p/139468429</a></p>
<h2>辐射能(Radiant energy) Q</h2>
<p>电磁辐射(electromagnetic radiation)的能量，单位是焦耳 J，用符号表示(很少用在计算机图形学中)：</p>
<p><img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=28eb8344174a720b375bb6334b39afe8&file=file.png" alt="" /></p>
<h2>辐射通量(Radiant flux)或功率(power) Φ</h2>
<p> 单位时间释放(emitted)、反射(emitted)、透射(transmitted)或接受(received)的能量。单位是 W 或lm
<img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=fcbceeb9bbb82a14d7d47be2469da258&file=file.png" alt="" /></p>
<h2>辐射强度(Radiant Intensity) I</h2>
<p>辐射(发光)强度是单位立体角(solid angle)由点光源发出的功率(power)
<img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=b0fbcd3c07167eab2050d8cd97c18231&file=file.png" alt="" /></p>
<h2>辐照度(Irradiance) E</h2>
<p>辐照度是每(垂直/投影)单位面积入射到一个表面上一点的辐射通量(功率)。单位：lux，照度(勒克斯)
<img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=e22feeb27b393db90005b08ee31687e2&file=file.png" alt="" /></p>
<h2>辐射(Radiance)或亮度(luminance) L</h2>
<p>是指一个表面在每单位立体角、每单位投影面积上所发射(emitted)、反射(reflected)、透射(transmitted)或接收(received)的辐射通量(功率)。</p>
<p><img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=b4466ce8b963eb8fd71c60ea65327177&file=file.png" alt="" /></p>
<h2>兰伯特余弦定律</h2>
<p>表面辐照度与光方向和表面法线夹角的余弦值成正比(也就是说只要在表面法线方向的的辐射度分量)</p>
<p><img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=d3baa097fa113c16ac3b9d42e28da2c0&file=file.png" alt="" /></p>
<h2>辐照度(Irradiance) VS. 辐射(Radiance)</h2>
<p><img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=0fd91b35bc03cab5d417f2c2ff429396&file=file.png" alt="" /></p>
<h2>辐照度衰减</h2>
<p><img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=8dd93fcceff9c7cde8ed37f6441cf197&file=file.png" alt="" /></p>
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<h2>微分立体角</h2>
<p><img src="https://www.showdoc.com.cn/server/api/attachment/visitFile?sign=c4307e4e4d7084575c3cdb1887fbacd0&file=file.png" alt="" /></p>
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