Yes, by all means use the variable reflection! It's not completely
realistic, but it is much better then flat reflectivity (heh). I think R2's
roughness is excessive. .001 might work better, but certainly your specular
setting will have to change as well. This will bring more metal feeling in
too. I think a reflection_min of eight-tenths to nine-tenths of your current
reflection (as reflection_max) will make you happy. Reflection_blur will
probably not satisfy you. JMHO

Hey, another scene to toy with shall always be graciously accepted! :)

Grim

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That is a really great rendering.  From the sand to the colors to the
textures.  Just great!

	And I think the problem with the shadow line is POV's problem.  You
see, in real life a light source will illuminate a surface less
efficiently the farther it is away from the surface normal.  So, as you
get closer and closer to the shadow line, the intensity of the highlight
should really trail off.  This is a *real physics* effect, but it is
less pronounced on rough surfaces. (like  when the rough bits peek up
over the horizon when everything around it is still in shadow)

	The problem with POV is that neither phong nor specular take this
effect into account, only diffuse does. (I don't know about Blinn...)

	Another *real physics* effect that you have some control over is the
size of the sun.  If you're not using an area light for the sun, I'd
suggest one.  On the earth, the sun's diameter takes up about 2 degrees
of the sky.  It really does have an effect if you look at the edges of
shadows cast by buildings and tree leaves, etc.  Maybe it would smooth
the shadow out over a couple of degrees around R2's dome.

BTW great render and great model!

In Him,
Ben

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which flavor would you prefer i post?  would you like it after i make my
first attempt at the new textures?  should be thursday night at the
latest.

GrimDude wrote:
> 
> Yes, by all means use the variable reflection! It's not completely
> realistic, but it is much better then flat reflectivity (heh). I think R2's
> roughness is excessive. .001 might work better, but certainly your specular
> setting will have to change as well. This will bring more metal feeling in
> too. I think a reflection_min of eight-tenths to nine-tenths of your current
> reflection (as reflection_max) will make you happy. Reflection_blur will
> probably not satisfy you. JMHO
> 
> Hey, another scene to toy with shall always be graciously accepted! :)
> 
> Grim

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any suggestions for size and placement of the sun?  i'm using 1 unit = 1
meter.

Ben Birdsey wrote:
> 
>         That is a really great rendering.  From the sand to the colors to the
> textures.  Just great!
> 
>         And I think the problem with the shadow line is POV's problem.  You
> see, in real life a light source will illuminate a surface less
> efficiently the farther it is away from the surface normal.  So, as you
> get closer and closer to the shadow line, the intensity of the highlight
> should really trail off.  This is a *real physics* effect, but it is
> less pronounced on rough surfaces. (like  when the rough bits peek up
> over the horizon when everything around it is still in shadow)
> 
>         The problem with POV is that neither phong nor specular take this
> effect into account, only diffuse does. (I don't know about Blinn...)
> 
>         Another *real physics* effect that you have some control over is the
> size of the sun.  If you're not using an area light for the sun, I'd
> suggest one.  On the earth, the sun's diameter takes up about 2 degrees
> of the sky.  It really does have an effect if you look at the edges of
> shadows cast by buildings and tree leaves, etc.  Maybe it would smooth
> the shadow out over a couple of degrees around R2's dome.
> 
> BTW great render and great model!
> 
> In Him,
> Ben

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By all means, take your time. I've got plenty to toy with :)

Flavor?

Grim

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ryan constantine wrote:
> 
> any suggestions for size and placement of the sun?  i'm using 1 unit = 1
> meter.
> 

Some time ago, we came to Diameter/Distance = 1/100 
(in Thread Radiosity test #2)

Of course this is only true for our local sun :-)

Christoph

--
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/

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"Ben Birdsey" <cla### [at] netscapenet> wrote in message
news:39C05E87.2C284B3D@netscape.net...
|
| Another *real physics* effect that you have some control over is the
| size of the sun.  If you're not using an area light for the sun, I'd
| suggest one.  On the earth, the sun's diameter takes up about 2 degrees
| of the sky.  It really does have an effect if you look at the edges of
| shadows cast by buildings and tree leaves, etc.  Maybe it would smooth
| the shadow out over a couple of degrees around R2's dome.

Unfortunately I don't think it's possible.  Area lights only effect shadows
as they fall onto other objects not the object creating the shadow.  I'm
sure many people have tried many times to get a area light to do this and
found the same thing.  Seems they will only affect the shadow which is cast
away from the object.  And the highlights don't change whether from point
sources or area lights either, same goes for the diffuse too I guess.  So
any such attempt is probably futile.

Bob

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flavor: moray or povray?

GrimDude wrote:
> 
> By all means, take your time. I've got plenty to toy with :)
> 
> Flavor?
> 
> Grim

Post a reply to this message

> Unfortunately I don't think it's possible.  Area lights only effect shadows
> as they fall onto other objects not the object creating the shadow.  I'm
> sure many people have tried many times to get a area light to do this and
> found the same thing.  Seems they will only affect the shadow which is cast
> away from the object.  And the highlights don't change whether from point
> sources or area lights either, same goes for the diffuse too I guess.  So
> any such attempt is probably futile.

i do remember that limitation of area lights, but that makes them faster
than a bunch of points right?  but how about a small array of points for
this?  or maybe spots?  can an angle of close to 180 be specified?  are
there any calculation speed ups with spots since light obviously can't
go behind them?  or are light calculations done another way?  and can
spot lights have their penumbra (is that the right word?) set to zero so
all light from the spot light is of the same intensity (ie no lateral
falloff)?  let's say i make a planet 70000 units in radius, how should i
go about finding the minimum acceptable distance (given the
size/distance ratio of 1/100 in christopher's post)?  would i use
different distances for spots than i would for points?  and what about
all those new keywords in megapov like circular and parallel?  might
they be of any use here?  has anyone ever done a looks_like to make a
sun?

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Basically, I agree with you.  The highlight position or shape won't
change and it won't get bigger, even though the light source is now
bigger.

	But, the block_area_light function basically figures out how much of
the area light is visible from any point and multiplies the phong or
specular or whatever highlight by that percentage.  This is totally
visible in this post.

	However, you can still see that POV cheats!  The sharp shadow line on
the second sphere wouldn't be there in reality, because part of the
light is still visible over the horizon.  There should be a smooth
transition.

	Well the idea works, but it looks like a 1:100 sun won't do anything
for you.

In Him,
	Ben

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