On 14/02/2014 6:20 PM, Stephen wrote:
> On 14/02/2014 5:02 PM, Kenneth wrote:
>> I
>> don't*think*  a sky_sphere can be made no_image (?). But I could be
>> wrong about
>> that.
>
> You could always use a large sphere with a spherical projection and the
> no image flag.
>
>

Oh! Very nice work. I forgot to say.

-- 
Regards
     Stephen

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"Kenneth" <kdw### [at] gmailcom> wrote:
>  The problem with using a sky_sphere is that my
> police car renders need a transparent background (for compositing later); I
> don't *think* a sky_sphere can be made no_image (?). But I could be wrong about
> that.

No, you are not wrong.  Luckily, POV-Ray has a built-in sphere primitive.  :-)
__________________________________________________

//+ua
#version 3.7;

global_settings { assumed_gamma 1 }

#include "colors.inc"
#include "skies.inc"

sphere
{ 0, 1
 //Substitute your image map
  texture
  { pigment
    { gradient y color_map
      { [0 rgb <0.4, 0.6, 1.0>]
        [1 rgb <0.10, 0.15, 0.30>]
      }
    }
    finish { ambient 0 diffuse 0 emission 1 }
  }
  texture { T_Cloud1 scale 0.1 }
 //
  scale 10000
  hollow
  no_image
}

light_source
{ <-1, 1, -1> * 5000, rgb <1.4716, 1.0775, 0.6379>
  parallel point_at 0
}

camera
{ location <0, 0.75, -5>
  look_at <0, 1, 0>
  angle 40
}

plane { y, 0 pigment { checker rgb 0.05 rgb 1 } }

sphere
{ y, 1
  pigment { rgb <0.61, 0.61, 0.64> }
  finish
  { reflection { 1 metallic }
    ambient 0 diffuse 0
    specular albedo 1 metallic roughness 0.0001
  }
}

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Attachments:
Download 'kenneth-alpha_sky.png' (53 KB)

Preview of image 'kenneth-alpha_sky.png'

Stephen <mca### [at] aolcom> wrote:

> >
> > You could always use a large sphere with a spherical projection and the
> > no image flag.

Yeah, that's what I'm doing now.

What I *really* need to do-- for this project and others-- is to buy a shiny
sphere, for making a 'light probe' (a non-HDRI version, as my little Canon video
camera doesn't shoot HDRI/'raw' images, unfortunately.) Then I could photograph
the surrounding 'environment' in just a single image (or two? I'm still not sure
of how light probes are made) and map that to the large no_image sphere. In the
past, I've simply stitched lots of 'normal' photos together, to get a
quasi-360-degree image for reflections. What a pain.

> Oh! Very nice work. I forgot to say.

Many thanks!

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"Kenneth" <kdw### [at] gmailcom> wrote:

>
> What I *really* need to do-- for this project and others-- is to buy a shiny
> sphere, for making a 'light probe' (a non-HDRI version, as my little Canon video
> camera doesn't shoot HDRI/'raw' images, unfortunately.)

Of course, there's the alternate trick of making, say, five bracketed exposures
of the mirrored sphere with my 'regular' camera, and then combining those in
specialized software to make an HDRI image. But I haven't gotten into the HDRI
world yet, sad to say. "So little time, so MUCH to learn." ;-)

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"Kenneth" <kdw### [at] gmailcom> wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>
> >
> > What I *really* need to do-- for this project and others-- is to buy a shiny
> > sphere, for making a 'light probe' (a non-HDRI version, as my little Canon video
> > camera doesn't shoot HDRI/'raw' images, unfortunately.)
>
> Of course, there's the alternate trick of making, say, five bracketed exposures
> of the mirrored sphere with my 'regular' camera, and then combining those in
> specialized software to make an HDRI image. But I haven't gotten into the HDRI
> world yet, sad to say. "So little time, so MUCH to learn." ;-)

This is pretty cool!

I have a 5 inch chrome sphere that I use for that very purpose (plus it looks
cool on my desk when not in use). Mount your camera on a tripod and take a set
of bracketed shots, then rotate the tripod ~90 degrees around the sphere and
take another set of bracketed shots. After you've combined the two bracketed
imagesets into 2 HDRs you can merge these offset images to eliminate the
camera/tripod completely from the final shot. Of course, Ive's IC is very useful
here:

http://www.lilysoft.org/IC/ic_index.htm

-------------------------------------------------
www.McGregorFineArt.com

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> "Kenneth" <kdw### [at] gmailcom> wrote:
>
>>
>> What I *really* need to do-- for this project and others-- is to buy a shiny
>> sphere, for making a 'light probe' (a non-HDRI version, as my little Canon video
>> camera doesn't shoot HDRI/'raw' images, unfortunately.)
>
> Of course, there's the alternate trick of making, say, five bracketed exposures
> of the mirrored sphere with my 'regular' camera, and then combining those in
> specialized software to make an HDRI image. But I haven't gotten into the HDRI
> world yet, sad to say. "So little time, so MUCH to learn." ;-)
>
>
>
I don't think that any camera can take HDR images natively.
For combining the bracketed images, there is hdrshop. A nice little 
utility just for that purpose. It can also transform a reflective sphere 
probe to a latitude-longitude one that you can then apply to a large 
sphere or sky_sphere using the spherical mapping.


Alain

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On 14/02/2014 8:26 PM, Kenneth wrote:
> "So little time, so MUCH to learn.";-)

Seconded. :-)

-- 
Regards
     Stephen

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> "Kenneth" <kdw### [at] gmailcom> wrote:
>
>>
>> What I *really* need to do-- for this project and others-- is to buy a shiny
>> sphere, for making a 'light probe' (a non-HDRI version, as my little Canon video
>> camera doesn't shoot HDRI/'raw' images, unfortunately.)
>
> Of course, there's the alternate trick of making, say, five bracketed exposures
> of the mirrored sphere with my 'regular' camera, and then combining those in
> specialized software to make an HDRI image. But I haven't gotten into the HDRI
> world yet, sad to say. "So little time, so MUCH to learn." ;-)
>
>

http://news.povray.org/povray.binaries.images/message/%3Cweb.44468657f8d220636c4803960%40news.povray.org%3E/#%3Cweb.44468657f8d220636c4803960%40news.povray.org%3E

   IIRC, that worked nicely, and additionally you have the fun of doing 
it with POV-Ray... :)

--
Jaime

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Jaime Vives Piqueres <jai### [at] ignoranciaorg> wrote:

>
>
http://news.povray.org/povray.binaries.images/message/%3Cweb.44468657f8d220636c4803960%40news.povray.org%3E/#%3Cweb.4
4468657f8d220636c4803960%40news.povray.org%3E
>
>    IIRC, that worked nicely, and additionally you have the fun of doing
> it with POV-Ray... :)
>

That is fascinating!!  Thanks for posting the link; I had not seen it before. I
can certainly make use of Trevor's sophisticated code ideas: Awhile ago, I tried
writing some similar (though inferior) code to do this kind of 'HDRI conversion
in POV-Ray', but got rather bland results. I see now what I was doing wrong.

Thanks! (And to Trevor too!)

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"Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:

>
> I have a 5 inch chrome sphere that I use for that very purpose (plus it looks
> cool on my desk when not in use). Mount your camera on a tripod and take a set
> of bracketed shots, then rotate the tripod ~90 degrees around the sphere and
> take another set of bracketed shots. After you've combined the two bracketed
> imagesets into 2 HDRs you can merge these offset images to eliminate the
> camera/tripod completely from the final shot. Of course, Ive's IC is very useful
> here:
>
> http://www.lilysoft.org/IC/ic_index.htm
>

So the 90-degree image is simply to get a clean area to 'replace' the
camera-plus-photographer in the original straight-on image? That makes perfect
sense. Here's a question, though: Is the *final* light probe ultimately made
from BOTH of those images? (Meaning: Is the 'corrected' straight-on image
somehow combined WITH the (similarly-corrected) 90-degree image to get a light
probe that has MORE environment imagery in it? Or is only the straight-on image
used?)

There's also something *mysterious* about light probes that I still have trouble
grasping: In my research into the subject, several sources stated that the
mirrored ball actually gathers environment imagery from BEHIND itself-- in the
spatial hemisphere out of view of the camera(!)-- implying that the very edges
of the ball pick up the 'hidden' back-side environment. Is that true (or even
possible?)

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