有趣的软阴影PAPER之间互评

2006年出了两篇关于SOFT SHADOW MAPS论文：
《Soft Shadow Maps： Efficient Sampling of Light Source Visibility》和
《Real-time soft shadow mapping by backprojection》
他们不同大学分别做出的类似技术。都是使用SHADOW MAPS处理和模糊阴影边缘。软阴影方面虽然SHADOW VOLUME走得更远，但随着梯形SHADOW MAPS，对数SHADOW MAPS等一些变形SHADOW MAPS成熟，硬件支持如果更加重视，也许未来阴影实用话方面SHADOW MAPS能够超过VOLUME。毕竟VOLUME在模糊阴影边缘方面有天生得弱势。PRT或者其他的谐和函数方法模拟动态或静态的低频光源，或许是软阴影的另一个方向。今后有时间把SHADOW一节展开来记录一下。
先看看这两篇相同时间相同内容的PAPER，它们是如何互相评价的.

from:
Guennebaud et al. [GBP06]（就是下一篇） also used the back projection
of each pixel in the shadow map to compute the soft shadow.
Their method was developed independently of ours, yet is
very similar. The main differences between the two methods
lie in the order of the computations: we compute the soft
shadow in shadow map space, while they compute the soft
shadow in screen space, requiring a search in the shadow
map.。。。言下之意，多一道手续，慢。。。
说到自己的缺陷：
Our algorithm also has some limitations when compared
to existing algorithms. First, our algorithm splits scene geometry
into occluders and receivers and self shadowing is
not accounted for. Also, since our algorithm uses shadow
maps to approximate occluder geometry, it inherits the well
known issues with aliasing from shadow map techniques.
For large area light sources, the soft shadows tend to blur
the artifacts but for smaller area light sources, such aliasing
is apparent.
 这个方法没有自阴影。。。遮挡物和接受物必须分开。受限很小的SHADOW MAP（应该指occluder map）。当面光源比较小后，走样比较明显。
看一下另一篇
from:
In a very recent work [AHL*06], Atty et al. have
presented a soft shadow algorithm whith a percentage of
visibility computation based, as in our approach, on the back
projection of the shadow map samples. However, unlike
our algorithm, their method relies on a very restrictive
assumption: occluders and receivers are disjointed sets.
Moreover, they are limited to very small shadow map
resolution (they report 200×200 pixels) and because all
visibility computations are done in the discrete shadow map
space, shadows are more aliased. 真是直接。。。