Carmack On Shadows

I see over at Doom3HQ that a certain Sebastian Sylvan emailed John Carmack with one of those high-tech questions he is so good at answering. Specifically he asked why stencil shadows were used over shadow buffers. Here's the response, which might mean more to you than to me:

Shadow buffers make good looking demos with controlled circumstances, but
when you start using them for a "real" application, you find that you need absolutely massive resolution to get acceptable results for omnidirectional lights, and a lot of the artifacts need to be tweaked on a per-light basis.

While it is possible to do shadow buffers on GF1/radeon class hardware,without percentage closer filtering they look wretched.

If we were targeting only the newest hardware, shadow buffers would have a better shot, but even then, they have more drawbacks than are commonly appreciated.

Well, duh.

Share this post


Link to post

Interesting....

nah! I wish I could undestand what are they talking about :-)

Share this post


Link to post
Vegeta said:

nah! I wish I could undestand what are they talking about :-)

They are talking about shadows.

Share this post


Link to post

This is also evident in the quake3-engine games... although less pronounced because the shadow rendering is simplified. go back to quake1, and you'll see a similar thing with lightmaps on the textures as a problem if there are several varied light sources.
still, I think these are petty... we want the Doom3 demo dammit! :)

Share this post


Link to post

God bless John Carmack. He could pump Doom III up full of features so that only those who owned godlike hardware could play it, but he's still looking out for those of us with only demigodlike hardware. Isn't he the greatest? Of course, like it's been said, it'll probably be like trying to run Doom on a 386, which isn't too great as I have problems running Doom on my slow 486 (I used to have a fast one, but I lost it), but it's the thought that counts. Frankly, if I have to run Doom III at 640x480 with low detail, if it'll run full speed I'll be in heaven. Of course, I'm starting to save up for a new computer, one that can take Doom III in all it's glory, but until then, all I really want to do is play it.

Share this post


Link to post

geforce 3 isnt "targetting only recent platforms"? heh

Share this post


Link to post
fraggle said:

geforce 3 isnt "targetting only recent platforms"? heh


Not by the time Doom3 is released :P

Share this post


Link to post

Now this is where Doom 3 really shines. The tricks that JC is pulling to get the high poly feel have all been done before, just in seperate locations, but it's the lighting and sound engines that are really going to blow away the competition. No one has done anything of this quality before. I can hardly wait... Screw getting dual clawhammers, I'd go single processor and drop the extra cash into a high-end sound system... Those lights in the demos are simply beautiful, and from what he's said so far, that's just the tip of the iceberg.

-Dan

Share this post


Link to post

Are you threatening me?

Share this post


Link to post

Those stenciled shadows look rather crap coparing those in Severance. Atleast have them transparent and not just completely black the area it shadow.

BTW SoM_ both severance and Neverwinter Nights have stenciled shadows and moving light sources... (this is reply to *way* earlier conversation about stenciled shadows in #zdoom)

Share this post


Link to post

Ebola, as has been pointed out before, various light sources cast various shadows. Ever notice the difference of shadows between sunlight, incadescent lightbulbs, and flourescent lightbulbs? This is similar as to what's going on in the screenshot. Look carefully at the shadows cast by the other actors, note the differences. It just so happens that the scientist guy has a sharp, bright light to his left, creating that crisp, dark shadow.

-Dan

Share this post


Link to post

No shadow is darker than the surrounding environment, not hit by the sharp light. That shadow is completely black. That, NEVER happens.
Plus. the same goes for the shadows in the Doom fotage movie

Share this post


Link to post

In Severance there were few lights in the scene, just like in Doom3, simply because the more lights affecting each poly, the slower the calculations become.

Severance doesn't have this kind of pitch black shadows simply because there is a global parameter defined "ambient light" that sets the minimum amount of illumation possible. This is rather crappy cause that forbids you of making dark rooms, something that Doom requires for its mood. In that scene, only the direct lightsource coming from the outside, used to fake the sun's illumination, is affecting that specific part of the installation. When there is only one light affecting a particular region, it's either pitch black because of occluding geometry or illuminated in some degree, defined by the light's intensity/range values.

Severance suffers from the exact same problem, only that they halved the lighting range.

Share this post


Link to post

Uhhh yeah, what Zald said. Also you don't know how recent those screenshots are. The game is still in development and I'm not going to take any thing seen yet as a finished product. I mean yes they were RELEASED recently but who knows exactly when they were taken. Or how complete the area was when it was taken. That scene might not even be in the game, not to mention everything is going to be moving around at the same time so its not like you are going to have a lot of time to spend staring at a shadow for lengths of time.

Share this post


Link to post

slow news week I take it ;)

as for the shadows, I always thought the pitch black looked kinda crumby, but hey, as Zaldron said, they need pitch black areas, so it's really just a necessary evil. hopefully they'll make 'em look better, but even if they don't, it's doom 3

commas = teh 1337

Share this post


Link to post

Just be grateful that they're giving us real time shadows at all.

Share this post


Link to post

Or even a Doom3 at all, for that matter.

Share this post


Link to post

Heh heh, it's kindof funny to watch people complain about how "it's not like real life".

Share this post


Link to post

Good Point, if I wanted life like I'd set up a military installation in my basement with cool ass lights all over and then have it invaded by hellspawn...Although I do agree, games aren't realistic, that's why they're games

Share this post


Link to post
kristus said:

No shadow is darker than the surrounding environment, not hit by the sharp light. That shadow is completely black. That, NEVER happens.


alright then, you find a way to simulate radiosity real time.

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now