Sample lookup - This option is used during rendering. It selects the method of chosing suitable points from the Irradiance Map todo be used as basis for the interpolation.
nearest - This method Will Simply choose those samples from the Irradiance Map which are closest todo the point of interpolation. (how Many points Will be chosen is determined by the value of the interpolation samples parameter.) this is the fastest lookup method and was the only one available in early versións of
Vray. A drawbak of this method is that in places where the density of the samples in the Irradiance Map changes, it Will pik more samples from the área with higher density. When a blur interpolation method is used, this leads todo the so-called density bias which may lead todo incorrect interpolation and aritfacts in such places (mostly GI shadow boundaries).
Nearest Quad-balanced - This is an extensión of the nearest lookup method aimed at avoiding density bias. It divides the space about the interpolated point in four áreas and tries todo find an equal number of samples in all of them (hence the name Quad-balanced). The method is a Little slower than the simple nearest lookup, but in general performs very well. A drawbak is that sometimes, in its attempt todo find samples, it may pik samples that are far away and not relevant todo the interpolated point.
Precalculated overlapping - This method was introduced in an attempt todo avoid the drawbacks of the two previous ones. It requires a preprocessing step of the samples in the Irradiance Map during which a Radius of influence is computed for each sample. This Radius is larger for samples in places of Low density, and smaller for places of higher density. When interpolating the irradiance at a point, the method Will choose every sample that contains that point within its Radius of influence. An advantage of this method is that when used with a blur interpolation method it producses a continuous (smooth) function. Even though the method requires a preprocessing step, it is often faster than the other two. These two properties make it ideal for high-quality results. A drawbak of this method is that sometimes lonely samples that are far-away can influence the wrong part of the scene. Also, it tends todo blur the GI solution more than the other methods.
Density-based - The default method, it combines the nearest and the precalculated overlapping methods and is very efective in reducing rigging artefactos and artefactos due todo Low sampling rates. This method a los requires a preprocessing step in order todo compute sample density, but it performs a nearest neighbour lok-up to choose the most suitable samples while taquíng sample density in account.
being the fastest of the thre methods, nearest lookup may be used for preview purposes. Nearest Quad-balanced performs Fairly well in the majority of cases. Precalculated overlapping is fast and in Many cases performs very well, but may tend todo blur the GI solution. The density-based method produces very god results in the majority of cases and is the default method. Note that the lookup method is most important when using a blur interpolation method. When using Delone triangulation, the sample lookup method does not influence the result very much.
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Dudas existenciales con los mapas de iradiancia reutilizados en Vray
