Howdy!

I have a strange effect while rendering a height field.
There are some black dots on it in some places and I don't
know what to do with it. I read the povray VFAQ and found
there something about that. But the only solution I found
was changing position of a camera. I've tried it many times,
but to no avail. There are too many black dots, so if one
disappears, there appears another in different place. Any
ideas of what should I do? Any patches? Thanks in advice.

--
Wojtek Bauman aka reaver | rea### [at] spleenwawpl | ICQ: 3429749 |
http://reaver.spleen.waw.pl | PGP: finger bauman@inx.pm.waw.pl |

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What version and platform are you running there?
Did you try the 'smooth' keyword yet? Just in case it's jaggedly
contoured.

Bob

Wojtek Bauman <rea### [at] spleenwawpl> wrote in message
news:37bf183e@news.povray.org...
> Howdy!
>
> I have a strange effect while rendering a height field.
> There are some black dots on it in some places and I don't
> know what to do with it. I read the povray VFAQ and found
> there something about that. But the only solution I found
> was changing position of a camera. I've tried it many times,
> but to no avail. There are too many black dots, so if one
> disappears, there appears another in different place. Any
> ideas of what should I do? Any patches? Thanks in advice.
>
> --
> Wojtek Bauman aka reaver | rea### [at] spleenwawpl | ICQ: 3429749 |
> http://reaver.spleen.waw.pl | PGP: finger bauman@inx.pm.waw.pl |
>
>

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Bob Hughes wrote:
> 
> What version and platform are you running there?
> Did you try the 'smooth' keyword yet? Just in case it's jaggedly
> contoured. 

I tried it. I also tried increasing max_trace_level,
max_intersections
and adc_bailout, but that didn't help.

-- 
Wojtek Bauman aka reaver | rea### [at] spleenwawpl | ICQ: 3429749 |
http://reaver.spleen.waw.pl | PGP: finger bauman@inx.pm.waw.pl |

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Wojtek Bauman wrote:
> 
> Bob Hughes wrote:
> >
> > What version and platform are you running there?
> > Did you try the 'smooth' keyword yet? Just in case it's jaggedly
> > contoured.
> 
> I tried it. I also tried increasing max_trace_level,
> max_intersections
> and adc_bailout, but that didn't help.
> 
> --
> Wojtek Bauman aka reaver | rea### [at] spleenwawpl | ICQ: 3429749 |
> http://reaver.spleen.waw.pl | PGP: finger bauman@inx.pm.waw.pl |

One thing that MAY be happening though you did not mention is it is that
you are using a very low resolution image for the HF and have very sharp
transitions in the height values of the HF itself. Sometimes I have seen
"cracking" in these situations and the fix in my case was to increase the
size of the image used to make the HF from.

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

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Ken wrote:
> 
> Wojtek Bauman wrote:
> >
> > Bob Hughes wrote:
> > >
> > > What version and platform are you running there?
> > > Did you try the 'smooth' keyword yet? Just in case it's jaggedly
> > > contoured.
> >
> > I tried it. I also tried increasing max_trace_level,
> > max_intersections
> > and adc_bailout, but that didn't help.
> 
> One thing that MAY be happening though you did not mention is it is that
> you are using a very low resolution image for the HF and have very sharp
> transitions in the height values of the HF itself. Sometimes I have seen
> "cracking" in these situations and the fix in my case was to increase the
> size of the image used to make the HF from.
> 
> --
> Ken Tyler

Hmm... That may help. I'll try to do what you said. Thanks.

-- 
Wojtek Bauman aka reaver | rea### [at] spleenwawpl | ICQ: 3429749 |
http://reaver.spleen.waw.pl | PGP: finger bauman@inx.pm.waw.pl |

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Howdy

I resized the image I made a HF from (width*2, height*2) and all the
black spots disappeared.
Thank you again.

-- 
Wojtek Bauman aka reaver | rea### [at] spleenwawpl | ICQ: 3429749 |
http://reaver.spleen.waw.pl | PGP: finger bauman@inx.pm.waw.pl |

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Wojtek Bauman wrote:
> 
> Howdy
> 
> I resized the image I made a HF from (width*2, height*2) and all the
> black spots disappeared.
> Thank you again.

  Your welcome. This is a good time to point out to anyone who uses height
fields in their scenes that the resolution quality of your HF is directly
proportional to the resolution of the image used to create it. The higher
the resolution of the image the higher the resolution your HF can have. I
generally use nothing less the 600x600 unless it will be used for something
minor like a rust spot on a piece of metal or the HF is used for something
like gently rolling hills. If there are any large variations in the heights
in adjacent areas the larger resolutions become more critical and can also
greatly reduce gridding and cracking as is often a complaint where HF's are
used.
  Another point to consider is the color depth of the image used. If you
use an 8 bit 256 color image for your HF you are limited to the number of
Hf values that can be obtained to 256 total values. If on the other hand
you use a 16 bit 16 million color image you have considerably greater
control over how many different height values are possible in the HF
itself. There is good reason why the Pov team added the hf_gray_16 option
and this is to allow you greater control of the use of HF's in your scenes.

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

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What type of image do you normally use?  Is there one better than the
other.  I'm going to use tga, but what about the others?

Ken wrote:
> 
> Wojtek Bauman wrote:
> >
> > Howdy
> >
> > I resized the image I made a HF from (width*2, height*2) and all the
> > black spots disappeared.
> > Thank you again.
> 
>   Your welcome. This is a good time to point out to anyone who uses height
> fields in their scenes that the resolution quality of your HF is directly
> proportional to the resolution of the image used to create it. The higher
> the resolution of the image the higher the resolution your HF can have. I
> generally use nothing less the 600x600 unless it will be used for something
> minor like a rust spot on a piece of metal or the HF is used for something
> like gently rolling hills. If there are any large variations in the heights
> in adjacent areas the larger resolutions become more critical and can also
> greatly reduce gridding and cracking as is often a complaint where HF's are
> used.
>   Another point to consider is the color depth of the image used. If you
> use an 8 bit 256 color image for your HF you are limited to the number of
> Hf values that can be obtained to 256 total values. If on the other hand
> you use a 16 bit 16 million color image you have considerably greater
> control over how many different height values are possible in the HF
> itself. There is good reason why the Pov team added the hf_gray_16 option
> and this is to allow you greater control of the use of HF's in your scenes.
> 
> --
> Ken Tyler
> 
> See my 850+ Povray and 3D Rendering and Raytracing Links at:
> http://home.pacbell.net/tylereng/index.html

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Nick Portelli wrote:
> 
> What type of image do you normally use?  Is there one better than the
> other.  I'm going to use tga, but what about the others?

  I personaly use .tga files but I suppose there is no reason that you cannot
use .gif for 8 bit 256 color HF images and .bmp and .png are also acceptable
for use as 16 bit 16 million color images. It should also be noted that you
can also use 24 bit images for HF's but internaly they will be represented
as 16 bit and the extra is ignored.
  The reason I use .tga is I often either create my HF images using povray's
hf_gray_16 option and my standard output is tga. Also the program Leveller
which I have tested a bit here and there also outputs a hf_gray_16 .tga file
that is similar in construction to Pov's internal version of it.

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

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Wojtek Bauman <rea### [at] spleenwawpl> wrote:
: I tried it. I also tried increasing max_trace_level,
: max_intersections
: and adc_bailout, but that didn't help.

  Increasing adc_bailout will actually lower the quality of the image but
makes rendering faster (although it has effect only if you have many
relfective/refractive surfaces).

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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