I've tried to make some user-friendly and instructive headers for crater.pov
and crater_dat.pov, but I'm no expert in file formats so I'd appreciate if
people who knows more about it than me would check if it's all correct and
if maybe it could be worded better.

Header comments in crater.pov:
// Persistence Of Vision raytracer version 3.5 sample file.
// CRATER.POV
// Render CRATER_DAT.POV to create the height_field image that
// is needed in CRATER.POV (this file). Then render this file.
//
// ( When CRATER.POV is rendered, the output image type must be
// the same as when CRATER_DAT.POV was rendered. That is how it
// works when no image type is specified in the height_field.
// Alternatively you can specify the image type of the
// height_field object in line 23 in CRATER.POV. See the
// documentation for details. )

Header comments in crater_dat.pov:
// Persistence Of Vision raytracer version 3.5 sample file.
// CRATER_DAT.POV
// Render CRATER_DAT.POV (this file) to create the height_field
// image that is needed in CRATER.POV. Then render CRATER.POV.
//
// ( You can use any output image type, but the quality will be
// best with the special 16-bit gray output that is supported
// by the PNG, TGA and PPM image types. See the documentation
// for details. )

Rune

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"Rune" <run### [at] mobilixnetdk> wrote in message
news:3bee7107@news.povray.org...
> I've tried to make some user-friendly and instructive headers for crater.pov
> and crater_dat.pov, but I'm no expert in file formats so I'd appreciate if
> people who knows more about it than me would check if it's all correct and
> if maybe it could be worded better.
>

As far as I can tell it appears to be well worded, and I believe it is correct
technically.

Michael

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Rune wrote:
> 
> I've tried to make some user-friendly and instructive headers for crater.pov
> and crater_dat.pov, but I'm no expert in file formats so I'd appreciate if
> people who knows more about it than me would check if it's all correct and
> if maybe it could be worded better.

It seems good.

> Header comments in crater.pov:
> // Persistence Of Vision raytracer version 3.5 sample file.
> // CRATER.POV
> // Render CRATER_DAT.POV to create the height_field image that
> // is needed in CRATER.POV (this file). Then render this file.
> //
> // ( When CRATER.POV is rendered, the output image type must be
> // the same as when CRATER_DAT.POV was rendered. That is how it
> // works when no image type is specified in the height_field.
> // Alternatively you can specify the image type of the
> // height_field object in line 23 in CRATER.POV. See the
> // documentation for details. )
> 
> Header comments in crater_dat.pov:
> // Persistence Of Vision raytracer version 3.5 sample file.
> // CRATER_DAT.POV
> // Render CRATER_DAT.POV (this file) to create the height_field
> // image that is needed in CRATER.POV. Then render CRATER.POV.
> //
> // ( You can use any output image type, but the quality will be
> // best with the special 16-bit gray output that is supported
> // by the PNG, TGA and PPM image types. See the documentation
> // for details. )

Perhaps indicate here the command line switches and ini settings
that allow such formats?

-- 
Adrien Beau   adr### [at] freefr   http://adrien.beau.free.fr/

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"Adrien Beau" wrote:
> Perhaps indicate here the command line switches
> and ini settings that allow such formats?

Well, this is where my knowledge doesn't suffice.

For example, to get 16 bit grayscale png I'm not sure if one has to use
+fn16 or if just +fn is enough when hf_gray_16 is specified in the
global_settings.

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:    http://rsj.mobilixnet.dk (updated Nov 5)
POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk

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"Rune" <run### [at] mobilixnetdk> wrote in message
news:3beffbe3@news.povray.org...
> "Adrien Beau" wrote:
> > Perhaps indicate here the command line switches
> > and ini settings that allow such formats?
>
> Well, this is where my knowledge doesn't suffice.
>
> For example, to get 16 bit grayscale png I'm not sure if one has to use
> +fn16 or if just +fn is enough when hf_gray_16 is specified in the
> global_settings.

I think the confusion is because of the 16 bit hf_gray_16 being in reality a
24 bit image.  I never understood if the PNG output was done in a different
way from the TGA, where it might also only use 16 bits of the whole.  When I
check for colors used I see something like a 256 color image instead, for
both PNG and TGA.
Anyway, the usual way is to use default 24 bit output, or +fn or +ft.  If it
were +fn16 you would get a 48 bit image.  Which BTW is mentioned in the Doc
under Height Field as being a better grayscale image.  I've yet to see that
to be true.
That said, all I ever get is 8 bit output for PNG grayscale images.  And I
don't think I have a viewer capable of seeing 48 bit images, they reduce to
24 in my image programs; either that or the output is always truncated.

Bob H.

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On Mon, 12 Nov 2001 12:53:58 -0600, Bob H. wrote:
> "Rune" <run### [at] mobilixnetdk> wrote in message
> news:3beffbe3@news.povray.org...
>> "Adrien Beau" wrote:
>> > Perhaps indicate here the command line switches
>> > and ini settings that allow such formats?
>>
>> Well, this is where my knowledge doesn't suffice.
>>
>> For example, to get 16 bit grayscale png I'm not sure if one has to use
>> +fn16 or if just +fn is enough when hf_gray_16 is specified in the
>> global_settings.

Yes.  (hf_gray_16 forces a PNG to 16-bpp.)
 
> I think the confusion is because of the 16 bit hf_gray_16 being in reality a
> 24 bit image.  I never understood if the PNG output was done in a different
> way from the TGA, where it might also only use 16 bits of the whole. 

It is done in a different way.  PNG images can be single-channel.  Here's
the output from pngcheck for a POV-generated hf_gray_16 PNG:

[ron]$ ./pngcheck sig2.png
OK: sig2.png (320x240, 16-bit grayscale, non-interlaced, 83.6%).

> When I
> check for colors used I see something like a 256 color image instead, for
> both PNG and TGA.

I think that's a limitation of whatever software you're using.

> Anyway, the usual way is to use default 24 bit output, or +fn or +ft.  If it
> were +fn16 you would get a 48 bit image.  Which BTW is mentioned in the Doc
> under Height Field as being a better grayscale image.  I've yet to see that
> to be true.

If 16-bpp PNG as an input format were working, I could demonstrate that it
is indeed true.  Since it isn't, at the moment, you'll have to take my word
for it.

-- 
plane{-z,-3normal{crackle scale.2#local a=5;#while(a)warp{repeat x flip x}rotate
z*60#local a=a-1;#end translate-9*x}pigment{rgb 1}}light_source{-9red 1rotate 60
*z}light_source{-9rgb y rotate-z*60}light_source{9-z*18rgb z}text{ttf"arial.ttf"
"RP".01,0translate-<.6,.4,.02>pigment{bozo}}light_source{-z*3rgb-.2}//Ron Parker

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"Bob H." wrote:
> 
> I think the confusion is because of the 16 bit hf_gray_16 being in reality a
> 24 bit image.  I never understood if the PNG output was done in a different
> way from the TGA, where it might also only use 16 bits of the whole.  When I
> check for colors used I see something like a 256 color image instead, for
> both PNG and TGA.
> Anyway, the usual way is to use default 24 bit output, or +fn or +ft.  If it
> were +fn16 you would get a 48 bit image.  Which BTW is mentioned in the Doc
> under Height Field as being a better grayscale image.  I've yet to see that
> to be true.
> That said, all I ever get is 8 bit output for PNG grayscale images.  And I
> don't think I have a viewer capable of seeing 48 bit images, they reduce to
> 24 in my image programs; either that or the output is always truncated.

I think it is starting to get confusing ;-)

With 'hf_gray_16' and +fn, Povray 3.5 in contrast to earlier versions is
supposed to generate 1 channel 16 bit output, but there is still a bug
leading to wrong byte order.  It is not possible to generate 8 bit
grayscale output right now.

Without 'hf_gray_16' you get 3 channel rgb output either 8 bit/channel
with +fn/+fn8 or 16bit/channel with +fn16.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

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Thanks Ron an Christoph!

I'd also like some more information on the PPM format. First of all, does it
work on all systems and operating systems? Second, how does it work
with/without hf_gray_16 and with/without 16bit specified?

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:    http://rsj.mobilixnet.dk (updated Nov 5)
POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk

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When I try to use a PNG with 16 bits per color as a height field, why does
POV-Ray say, "Warning: Converting PNG image map to 8 bits/sample from higher
bit depth."?

Anders

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In article <3bf0398e$1@news.povray.org> , "Anders K." <and### [at] f2scom> 
wrote:

> When I try to use a PNG with 16 bits per color as a height field, why does
> POV-Ray say, "Warning: Converting PNG image map to 8 bits/sample from higher
> bit depth."?

Good question.  Maybe a damaged PNG image?

Can anybody confirm such a message with any other PNG image?

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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