RE: [Algorithms] It looks terrible (was: Lightmap Terrain)

[Phil B. <ph...@de...>]

hey,

i do the same thing as you except i have one directional
light for the sun, cast the ray and then if it intersects
don't add on the diffuse just leaving the ambient.

i found i have to play with the sun's direction a lot
to get good results - really long shadows seem to look
a little weird for me.

>For example, is there a way to have real penumbrae in the
>shadows.

this is a fudge but what i've been doing is creating 7
lightmaps and then do something like...

GenerateLightmap( lightmap0, lightlist );
//x jitter by 10%
JitterLights( lightlist, 0.1, 0.0, 0.0 );
GenerateLightmap( lightmap1, lightlist );
JitterLights( lightlist, -0.1, 0.0, 0.0 );
GenerateLightmap( lightmap2, lightlist );
//y jitter by 10%
JitterLights( lightlist, 0.0, 0.1, 0.0 );
GenerateLightmap( lightmap3, lightlist );
JitterLights( lightlist, 0.0, -0.1, 0.0 );
GenerateLightmap( lightmap4, lightlist );
//z jitter by 10%
JitterLights( lightlist, 0.0, 0.0, 0.1 );
GenerateLightmap( lightmap5, lightlist );
JitterLights( lightlist, 0.0, 0.0, -0.1 );
GenerateLightmap( lightmap6, lightlist );

and then just average all the lightmaps into a final one.

all the jitter function is doing is changing the positions
of the lights... like i said, it's a big hack but those hard
shadows went soft immediately and look pretty good now.

the downside of course is that it takes a long time to
generate a final lightmap.

>I could blur the image, but that just wouldn't be the same.

i tried this before doing the above and couldn't get
anything decent too.

regards.

Phil Bak
ICQ:11204037 Tel:01908 393837 Email:ph...@de... Web:www.deepred.co.uk
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-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of Klaus
Hartmann
Sent: 27 August 2000 14:29
To: gda...@li...
Subject: [Algorithms] It looks terrible (was: Lightmap Terrain)


Hi all,

Please have a look at the following image (~310 KB):
http://www.thecore.de/TheCore/shadows.jpg

This lightmap looks majorly terrible, and I'm looking for ways to enhance
this. I use the simple dot-product approach, and I have two light source.
One light source (sun) is to the east, and the other ('anti' sun) is to the
west. I use two light sources, because I don't like ambient. I compute the
light for each texel, and then I cast a ray towards the sun (directional
light). If this ray intersect with the surface before it reaches the sun,
then I decrease the texel's intensity by some amount. I don't reflect or
refract rays. I figured, that reflection probably wouldn't make much sense,
because there's only a few cases where the reflected ray would hit the
terrain again (or am I wrong?).

How can I make this look better? For example, is there a way to have real
penumbrae in the shadows. Of course, I could blur the image, but that just
wouldn't be the same.

Any ideas? Honestly... a simple dot-product (without shadows) looks more
than twice as good (I can upload the same scene without shadows, if
requested).
Niki

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