學(xué)了
TracePro有一段時(shí)間了,一直沒(méi)有注意到
重點(diǎn)采樣這個(gè)功能,后來(lái)分析問(wèn)題的時(shí)候發(fā)現(xiàn)
光線(xiàn)追跡的時(shí)間會(huì)因?yàn)楣饩(xiàn)數(shù)太多會(huì)達(dá)到30分鐘甚至更多時(shí)間。了解有重點(diǎn)采樣這個(gè)東西后,我直覺(jué)就是可以解決用相對(duì)較少的光線(xiàn)數(shù)來(lái)解決問(wèn)題(直覺(jué)不科學(xué),哈),所以就開(kāi)始摸索。下面分享一下我的經(jīng)驗(yàn),我也有許多不會(huì)的,歡迎大家參加討論。
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xt|^~~ / 重點(diǎn)采樣在User's Manual里面的描述是:
DQGrXMpV0 26p[x'W Importance sampling is a Monte Carlo technique in which rays are generated and propagated in specific directions in the optical system, which are “important” in determining the results you need. This improves sampling by increasing the number of rays reaching the surface or surfaces of interest to the user. Importance sampling is essential in a stray light analysis, where the attenuation of incident light can be very great, and can be helpful in other types of analyses. In a stray light analysis, there should be an importance sampling target for each optical surface in the optical system. It is important to remember that importance sampling is used only to enhance the sampling of scattered and diffracted light or surface sources. Designs that include only specular reflection and transmission cannot take advantage of importance sampling — the direction of the rays is determined by the Law of Reflection and Snell’s Law. dFBFXy
Figure 7.1 on page 7.3 illustrates importance sampling for the simple case of a lens that scatters from its second surface. A second object is shown that corresponds to a detector. In this case rays from an off-axis field position are imaged such that all of the specular rays miss the detector. Generally, scattering is stronger close to the specular direction of the un-scattered ray so the probability of a randomly scattered ray hitting the detector is very small. When an importance target is applied, it guarantees that the one or more importance rays will hit the detector for each incident ray.
;`oK5 SnG(/1C8 自己嘗試翻譯一下為:
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