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

[Klaus H. <k_h...@os...>]

----- Original Message -----
From: Jim Offerman <j.o...@in...>
> Hey Niki,
>
> Some suggestions which might make your lightmap (and not to forget your
> terrain) look better/nicer. Maybe you have already considered these, but
> then again, you never know :-)
>
> - Perhaps you could use a lighter ambient color (instead of something
> nearing total blackness, say about 20-25% gray or something). Near black
> shadows are not really common in real life, specially not in open
terrains -
> always plenty of ambient light.

I don't use any ambient color at all. Instead I use a second directional
light source (opposite to the sun).

> - When raytracting your lightmap, you could perhaps use the corners of
each
> pixel/texel instead of the centers and then use the average of the four
> corners as the pixel's color, essentially applying a bilinear filter to
your
> light map.

I do use the pixel-corners, but I don't average them. This is sort of an
accident really. Perhaps, I should cast the rays through the center of each
pixel. Thanks for reminding me :)

> - It is just a hunch (no scientific basis, other than my own
observations),
> but it might look good if you lighten the shadow areas based on the slope
of
> the terrain, so that shadows on steep areas look darker than those on flat
> areas, which in my eyes also happens in reality. Reason for this effect
> could be that more diffuse light is being reflected on the flat areas by
the
> clouds, but again, I have no scientific basis for this assumption.

Funny! This is exactly what I did last night :) This made the lightmap look
a bit better, but I haven't tried it in 3D, yet.

Well, I think I'll bite the bullet and try some true recursive ray tracing
(with reflected rays), today. Technically this is wrong for diffuse light,
but maybe it looks better, and that's what counts.

Thanks,
Niki

>
> Jim Offerman
>
> Innovade
> - designing the designer
>
> ----- Original Message -----
> From: "Klaus Hartmann" <k_h...@os...>
> To: <gda...@li...>
> Sent: Sunday, August 27, 2000 6:32 PM
> Subject: Re: [Algorithms] It looks terrible (was: Lightmap Terrain)
>
>
> > Welcome, Ralf :)
> >
> > ----- Original Message -----
> > From: Ralf Schneider <rap...@ra...>
> > > Niki,
> > >
> > > well it do NOT look that terrible!
> > > it's a lightmap, isn't it? what du you suspect?
> >
> > What I suspect is a nice image :) See, I've actually tried this shadow
> stuff
> > in my terrain engine, and in 3D it looks far worse than the lightmap. I
> > tried this with a hybrid multifractal, though... maybe it looks better
> with
> > real world data as show in the image. Gotta try this, but it's a bit
more
> > work.
> >
> > > shadows make scenes nore realistic, not neccesarily beautiful.
> >
> > This is a good description. The unrealistic dot-product-only lit scene
(in
> > 3D) looks much better, even though it's not as realistic as the shadowed
> > version.
> >
> > >you are loosing visual information if yo add shadows to a top down view
> of
> > a heightfield. you know that already, because you are trying to avoid
it,
> by
> > using a second light source instead of ambient light (we can say the
> second
> > light is simulating the reflection of the sun at the other mountain...).
> >
> > Yes, this is quite a problem. If I use no second light source, then
> there's
> > zero shading on the faces opposite to the sun, which basically means
that
> I
> > lose all the nice features. If, on the other hand, I use a secondary
light
> > source (plus shadows), then I get artifacts as the one's in the
> upper-right
> > shadow-area of the image I posted. This looks as if I used false gays
(as
> in
> > false color). In 3D this becomes even worse.
> >
> > > take a look at some landscape/mountain top-down photos. i guess, you
> will
> > recognice you lightmap is ok!
> >
> > You should see John Ratcliff's work... I remember his moon-lightmap and
it
> > looks great. John, are you still a member of this list? Could you please
> > upload that moon-lightmap of yours again?
> >
> > Niki
> >
> >
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