Comments on: Deferred Cascaded Shadow Maps

By: Aras Pranckevičius

Aras Pranckevičius — Sun, 22 Nov 2009 12:00:38 +0000

@CodingCat: I just ignored the whole AA issue. So yes, when AA is used the shadow term is sometimes wrong on edges. So far I haven’t heard lots of complaints from Unity users, so I assume everyone is fine with that :)

By: CodingCat

CodingCat — Sun, 22 Nov 2009 10:11:38 +0000

I’m doing this pretty much the same way, but I had a very hard time making this work with anti-aliasing (DirectX 9). In the end, I added a resolve pass that tries to fill invalid gaps with some approximate shadow value (the darkest of all neighbors after applying some validity and continuity heuristics) to get rid of all the wrongly lit edges. This has artifacts of its own, but at least it doesn’t look totally wrong. The big drawback here is that this resolve pass is not separable and quite expensive.

Any experience on this issue?

By: Aras Pranckevičius

Aras Pranckevičius — Tue, 10 Nov 2009 06:30:25 +0000

@Alex: nice!

By: Alex

Alex — Tue, 10 Nov 2009 04:34:48 +0000

For the weights calculation, I used this formulation:
float4 weights = ( z > _LightSplitsNear );
weights.xyz -= weights.yzw;
The rest is the same.
_LightSplitsNear has to be ordered from nearest to furthest, the cascades should overlap, and if it’s past the furthest cascade’s far then ‘weights’ doesn’t return to all zeroes.

By: Simon Kozlov

Simon Kozlov — Thu, 05 Nov 2009 09:05:11 +0000

I did that around 2003 in my trucks game. Unfortunately Geforce3 didn’t allow me to do fancy blur scheme so it was just blurring outward with semi-acceptable radius.

Can still see artifacts on recent screenshots though :(

By: Tom

Tom — Wed, 04 Nov 2009 22:20:28 +0000

CryEngine 2 did something similar but stored the shadows for 4 different lights into the 4 channels of the screen space shadow buffer.

By: steve

steve — Wed, 04 Nov 2009 16:03:44 +0000

Yep, definitely deferred shadowing :) The variable sized filter and depth discontinuity discards are staples in SSAO too. Nice work!

By: Ste

Ste — Wed, 04 Nov 2009 14:52:00 +0000

This is very similar to one of Wolf Engel’s techniques in ShaderX5 i think :). Not sure if you’ve seen that or not.

By: repi

repi — Wed, 04 Nov 2009 14:47:44 +0000

Good post, and I like the term “deferred shadowing” for this as well!