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Shadows

Vilem Otte

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I was actually trying to avoid this topic as long as possible, but with my current updates on lighting system - I had to bump into it, and of course write about it.

So, when designing my lighting system I kept in mind few things I want to achieve with it - multiple light sources, that is a must have (especially when you're using deferred shading), all of those need to be used throughout the stages (global illumination, reflections, etc.), and I require all lighting to be dynamic and capable of casting shadows. Other than that multiple supported light types - point, spot, directional and area light sources, all supporting casting shadows.

While the lighting system is still not complete, shadows pretty much are. Or to be precise shadow filtering, a user needs to be able to select what shadow filtering method is light going to use (depending on the light importance, range and strength). So let's take a look at few examples of shadow filters available:

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Standard shadow mapping & PCF shadow mapping

tmp.thumb.jpg.57c0acf2b2e710e730d2d41af411b1ab.jpg

Bilinear shadow mapping & PCF + Bilinear shadow mapping

Are standard common filters well known and used. The advantage of these is that they are fast - and therefore possible to use for all lights. Yet they don't somehow seem realistic - especially for area lights, this is where more advanced filters are required.

tmp.thumb.jpg.81aa2ab9032feaf463ccdd2939837af6.jpg

Percentage closer soft shadows & Mip-map penumbrae shadow maps

Are advanced filters for area-based shadow maps, and allow for variable penumbra size. Note that the images might have a bit low bias, resulting in small artifacts (I didn't really fine tune anything for taking the images). These shadow filters should allow for most scenarios I can imagine (but technically if any other is required it can be added).



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