3e2471fa$1@news.povray.org...

> Well, I'm getting there. HDRI is a way of approximating real-life
situations
> that Pov-Ray can't do, or can't do well -- I'm thinking events like depth
of
> focus, glare, sun flares.

No it's much simpler and limited in scope. Just think of it as a photograph
able to emit bright light. It doesn't add functionality to POV-Ray (it's
possible to have HDRI effects in POV-Ray without a patch), it's just that
HDRI photographs derived from natural environments give very realistic
results when used in 3D pics because they are by definition realistic
(realistic colors AND realistic light intensities). One thing that gives
away images using HDR maps is that the reflection of light sources is not
dimmed on poorly reflective objects (the reflection of a light bulb will be
bright even if the object has refection 0.3).

In fact, here is a basic HDR texture in regular POV-Ray:
texture{
    image_pattern{jpeg "areas_of_light_intensities"}
    texture_map{
        [0 pigment{color White} finish{ambient 0}] // regular White
        [1 pigment{color White} finish{ambient 1000}] // very very bright
White
    }
}

> Next: is HDRI a program in itself?

No, it's a way to store the light intensities with the color pixels. There
are several file formats available (HDR, PIC, TIFF adaptations seem the most
frequent). What MLPOv has is the support for the HDR format. There's a free
program called HDRShop that lets you create and view HDR image though.

G.

--

**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters

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Slashdolt wrote:
>>
>
>I still don't feel I'm explaining this very well.  Maybe if I said something
>like, "To some extent, it's like radiosity coming from a photograph rather
>than from a light source bouncing off 3D objects in a completely rendered
>scene."
>
>Slash
>

Well, I haven't tried it yet, so I may be completely wrong, but if I
understand what I've seen here, both in comments and in images, the HRDI
image IS the light source.  That requires an image with higher values than
1.

Best example I can think of is in my frozen moment IRTC entry
(http://www.irtc.org/ftp/pub/stills/2002-12-31/hang_rg.jpg) I use a
terragen image as a background. I also had to use a lightsource with a fade
power of about 10 to get the light on the foreground to look right, not to
mention the time I spent getting it positioned to look right.  If I had
used an HRDI image I wouldn't have had to add the light source, the HRDI
image would take care of that and it would be right where it belonged.

And that is pretty much what I understand its intended for. Unfortunately,
the patch came out about three days after I submitted it or I probably
would have tried it, since it looks like terragen supports this with a
plug-in... :)

RG

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"Slashdolt" <nomail@nomail> wrote in message
news:web.3e247766552627465543301f0@news.povray.org...
> >Well, I'm getting there. HDRI is a way of approximating real-life
situations
> >that Pov-Ray can't do, or can't do well -- I'm thinking events like depth
of
> >focus, glare, sun flares.
> >
>
> Not quite.  It really has to do with one thing only, afaik.  Simply the
> lighting.
>
> By allowing some things to be brighter than simply "all-white" it allows
you
> to insert a 3D object into a "real life" photo, and have the same lighting
> in the room as you did when the photo was taken.  To use my "sun coming
> thru a window" analogy, your 3D object could actually be "lighted" from
> where the sun hits on the far side of the room indirectly, and not just
> from the actual light source.
>
> I still don't feel I'm explaining this very well.

No, actually that about did it. I'm rendering a statue in a white room.
There is one light source illuminating the side of the statue the camera is
looking at, meaning the other side is dark. HDRI bounces the light off the
white walls and illuminates (partially) the other side if the statue. Do I
have it now? That's pretty cool.

Mark

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In article <3e24a4da@news.povray.org>,
 "Mark Hanson" <mar### [at] attbicom> wrote:

> No, actually that about did it. I'm rendering a statue in a white room.
> There is one light source illuminating the side of the statue the camera is
> looking at, meaning the other side is dark. HDRI bounces the light off the
> white walls and illuminates (partially) the other side if the statue. Do I
> have it now? That's pretty cool.

No. Radiosity alone does that. HDRI just lets you encode the lighting 
values in a high dynamic range image, so you don't have to calculate it 
during rendering and can use real-world surroundings without having to 
model them.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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"Christopher James Huff" <cja### [at] earthlinknet> wrote in message
news:cja### [at] netplexaussieorg...
> > No, actually that about did it. I'm rendering a statue in a white room.
> > There is one light source illuminating the side of the statue the camera
is
> > looking at, meaning the other side is dark. HDRI bounces the light off
the
> > white walls and illuminates (partially) the other side if the statue. Do
I
> > have it now? That's pretty cool.
>
> No. Radiosity alone does that. HDRI just lets you encode the lighting
> values in a high dynamic range image, so you don't have to calculate it
> during rendering and can use real-world surroundings without having to
> model them.

Okay, I give up. :-) I don't know enough about higher-end rendering to
understand it. But I'll get there some day. Thanks to everyone.

Mark

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> Okay, I give up. :-) I don't know enough about higher-end rendering to
> understand it. But I'll get there some day. Thanks to everyone.

Do not give up!

HDRI is just the BITMAP, nothing more.
Its higher dynamics & lower bounds on intensity clamping give you
opportunity to use it as a source of data which is more real than
clamped & more discretized RGB map such PNG,BMP etc.

Its a BITMAP!   ... used in a very cheap way to light the scene or
place more dynamic reflections/refractions.... its a touch of reality in
the very clamped POVRAY world....

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On Mon, 3 Mar 2003 15:07:05 +0100, "T.J.Viking" <vik### [at] bp-domarpl> wrote:
> its a touch of reality in
> the very clamped POVRAY world

would you like to make "clamped" word usage more clear here?

ABX

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> would you like to make "clamped" word usage more clear here?

clamping (in GFX world) - clipping some values in suitable range


.. in POVRAY clamping occurs in final RGB discretization process, but also is
present in radiosity code i many places - the author of implementation had some
intention to make POV radiosity more artistic one.. rather than real one....

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On Mon, 3 Mar 2003 15:46:50 +0100, "T.J.Viking" <vik### [at] bp-domarpl> wrote:
> .. in POVRAY clamping occurs in final RGB discretization process, but also is
> present in radiosity code i many places - the author of implementation had some
> intention to make POV radiosity more artistic one.. rather than real one....

Gooood. I was affraid that you meant "POV community" as "POV world" which could
change "clamped" sense a lot.

Have you done some "unclamping" for radiosity code ? Have you some results ? Any
patched version available ?

ABX

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"ABX" <abx### [at] abxartpl> wrote in message
news:85r66vgt97vbv62ou75qoimr6qv89ju5oe@4ax.com...
>
> Gooood. I was affraid that you meant "POV community" as "POV world" which
could
> change "clamped" sense a lot.
>

Now, *THATS* paranoid.... ;)

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