Soft shadows in Doom3 engine

[Reverend]

First, re-visit this thread. There are some screenshots there showing how "soft" shadows can look like in the D3 engine. Explanations are also provided in the thread on how to take such "soft" shadows screenshots, if you never knew about this and are interested to try this (provided you have D3).

The reason for this thread is to ask :

1) How good the "soft" shadows look as seen in the screenshots
2) At what screenshot-grabbing rez and number of samples do the "soft" shadows start to look good?
3) What would be the current best method for real-time-in-game "soft" shadows, and what better methods can we expect (real-time again)?

Thanks.

 

[Simon F]

First, re-visit this thread. There are some screenshots there showing how "soft" shadows can look like in the D3 engine.

But are any links to images that aren't broken?

 

[Reverend]

Sorry, didn't check out the links beforehand. Here's a linked image (1.38MB) :



Rez + # of samples should be obvious from the name of the image.

 

[AlNom]

hm... I used to mess around with the number of samples for the screenshots... at some point the shadows pretty much disappeared i.e. very very faint, but it's different than not having shadows.


With all that stencil rendering power of those Geforce cards, especially with up to quad SLI, I don't see why it wouldn't be such a terrible idea to do soft shadows ala F.E.A.R. One could up the samples to make it look better too.. no?

 

[micron]

Here's a linked image (1.38MB) :

http://3dpulpit.hostingisfree.com/misc/d3_soft/d3_4x3_128sample.jpg

ewww.....what card rendered that?

 

[Andrew Lauritzen]

Just to be clear, these aren't "real" soft shadows, right (i.e. perceptually correct with contact hardening and so forth)? They're just super-sampled stencil shadows.

I must admit to still being partial to shadow maps (especially for soft shadows), but I'm interested in how expensive this solution is. How long did that frame take to render, and with how many samples?

 

[Malo]

Just to be clear, these aren't "real" soft shadows, right (i.e. perceptually correct with contact hardening and so forth)? They're just super-sampled stencil shadows.

I must admit to still being partial to shadow maps (especially for soft shadows), but I'm interested in how expensive this solution is. How long did that frame take to render, and with how many samples?

It's 128 samples from the filename.

 

[Razor1]

hm... I used to mess around with the number of samples for the screenshots... at some point the shadows pretty much disappeared i.e. very very faint, but it's different than not having shadows.


With all that stencil rendering power of those Geforce cards, especially with up to quad SLI, I don't see why it wouldn't be such a terrible idea to do soft shadows ala F.E.A.R. One could up the samples to make it look better too.. no?

Was thinking the same thing!

 

[nAo]

but I'm interested in how expensive this solution is.

It's much more expensive than your technique and still requires 'good' geometry to work well.

 

[Xmas]

Just to be clear, these aren't "real" soft shadows, right (i.e. perceptually correct with contact hardening and so forth)? They're just super-sampled stencil shadows.

I think these soft shadows are created by accumulating N passes with jittered light positions. With enough samples this should actually be pretty close to "real" soft shadows you would get from area or volume light sources. Except of course it does not take into account atmospheric scattering and reflected light.

I wonder how they keep the accuracy high enough for the accumulation with that many samples.

 

[Andrew Lauritzen]

I think these soft shadows are created by accumulating N passes with jittered light positions. With enough samples this should actually be pretty close to "real" soft shadows you would get from area or volume light sources.

Right, that's what I was wondering. So the light source is just jittered around within some (constant?) radius? That would indeed give "proper" soft shadows if enough samples are used.

It seems a bit expensive to me though in that you'd need at least 256 samples to avoid stair-stepping in the penumbrae... potentially more if doing HDR/tonemapping.

 

[pascal]

The picture above has 10+ steps

 

[AlNom]

Was thinking the same thing!

Hm... then again, I guess the geometry load would increase ridiculously. But hey, unified shaders!... that is, if the stencil algorithm benefits from a possible huge jump in VS resources. ( )

 

[jlippo]

Hm... then again, I guess the geometry load would increase ridiculously. But hey, unified shaders!... that is, if the stencil algorithm benefits from a possible huge jump in VS resources. ( )

It also has to calculate light for each pixel in each shadow pass, so it would stress pixel shaders quite nicely as well.
One of the good things is that it actually causes lights to be volumetric and thus lighting itself is more natural than in normal gameplay.