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29 Mar 2024 07:34:06 EDT (-0400)
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From: Thomas de Groot
Subject: Re: First image posting
Date: 3 May 2021 02:48:11
Message: <608f9cab$1@news.povray.org>
Op 03/05/2021 om 08:36 schreef Thomas de Groot:
> Op 02/05/2021 om 14:11 schreef Bald Eagle:
>> Thomas de Groot <tho### [at] degrootorg> wrote:
>>
>>>> Presumably, this is what all this "mip-mapping" business is about.   
>>>> Has anyone
>>>> ever tried to emulate that process, that we know of?
>>>>
>>> Good question. It would be interesting to try indeed. RoundTuits are
>>> needed however!
>>
>> https://www.youtube.com/watch?v=0flY11lVCwY
>> He covers this briefly in the first 2 minutes.
>>
>> Just shooting from the hip here, but it sounds like a functional 
>> emulation of
>> this would be to start with a very large, high-def version of the 
>> texture and

>> filenames and
>> the texture could probably be automagically sampled at the desired 
>> resolution
>> using a polynomial function like I did in the vortex scene or using a 
>> spline
>> like Ingo is doing.
>>
> By default, a factor 2 scaling is used, I understand. That is not 
> difficult; what is (at least for me) is how to chose the right texture 
> for each render or location in the scene (for instance the background of 
> a chequered plane smoothly grading into the foreground). Well, I have an 
> idea of course, but no time to test it out presently. :-/
> 
>> Maybe there's some kind of MOA (minutes of angle) calculation that 
>> initially
>> gets done to optimally set the different image_map resolutions...?
>>
> Hmm... possibly. I have no idea at this stage however.
> 

And I immediately come back to the matter as I suddenly realise that 
this would be a crucial technique for using the same granite textures 
(forgive me my present obsession with granites) in close foreground 
views and landscape-sized backgrounds. Or wouldn't it? Is mipmapping 
only useful with image_maps? The examples I have seen so far are just 
that. Could it be applied successfully to traditional POV-Ray textures?

-- 
Thomas


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From: jr
Subject: Re: First image posting
Date: 3 May 2021 03:25:00
Message: <web.608fa41ff7d27fe79819d986cde94f1@news.povray.org>
hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 03/05/2021 om 08:36 schreef Thomas de Groot:
> > Op 02/05/2021 om 14:11 schreef Bald Eagle:
> >> Thomas de Groot <tho### [at] degrootorg> wrote:
> >>
> >>>> Presumably, this is what all this "mip-mapping" business is about.
> >>>> ...
> ...
>  Could it be applied successfully to traditional POV-Ray textures?

no idea but reading yr exchange led me to this Wiki page:
<https://en.wikipedia.org/wiki/Mipmap>


regards, jr.


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From: Thomas de Groot
Subject: Re: First image posting
Date: 3 May 2021 04:20:00
Message: <608fb230$1@news.povray.org>
Op 03/05/2021 om 09:19 schreef jr:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> Op 03/05/2021 om 08:36 schreef Thomas de Groot:
>>> Op 02/05/2021 om 14:11 schreef Bald Eagle:
>>>> Thomas de Groot <tho### [at] degrootorg> wrote:
>>>>
>>>>>> Presumably, this is what all this "mip-mapping" business is about.
>>>>>> ...
>> ...
>>   Could it be applied successfully to traditional POV-Ray textures?
> 
> no idea but reading yr exchange led me to this Wiki page:
> <https://en.wikipedia.org/wiki/Mipmap>
> 
Thanks, yes, I also found that page indeed :-)

Well, should have done that first of all, but the following (hot) 
discussion about mimapping with POV-Ray from 2005 can be found here:
http://news.povray.org/povray.newusers/thread/%3C4282a2e9%40news.povray.org%3E/

I conclude from that, that aa is the ray-tracing answer to mipmapping, 
and I guess that my initial suggestion of stochastic aa is the correct one.

-- 
Thomas


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From: jr
Subject: Re: First image posting
Date: 3 May 2021 05:15:00
Message: <web.608fbe56f7d27fe79819d986cde94f1@news.povray.org>
hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 03/05/2021 om 09:19 schreef jr:
> > ...
> I conclude from that [thread], that aa is the ray-tracing answer to mipmapping,
> and I guess that my initial suggestion of stochastic aa is the correct one.

taking the 'El Capitan' cliff face as an example, say I want to render two
images: object near base of, and object some distance from.  then I need to
choose a scale for the texture(s)?  I think that I (as in "numpty" etc) would
benefit from having some row/col table, in the documentation and or as array, of
all parameters involved ("lambda", "octave", such) by scale/suggested distance
(in POV-units?).  (and perhaps a macro which expands to the texture at the given
scale/index)  (just thinking aloud :-))


regards, jr.

btw, re "graveyards".  had to put on an anorak, even for a cursory read.  :-)
found out that what I associate with "granite" really is "dolerite".  thanks.


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From: Bald Eagle
Subject: Re: First image posting
Date: 3 May 2021 06:35:00
Message: <web.608fd1a5f7d27fe1f9dae3025979125@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
what is (at least for me) is how to chose the right texture
> for each render or location in the scene (for instance the background of
> a chequered plane smoothly grading into the foreground).

I guess you could have a macro generate the texture, and have an AutoScale
argument.  The distance from the camera to the closest object (user-supplied
value) could be used to set the scale.  Might need to set a pov unit = real
world measurement ratio and base everything off that.


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From: Thomas de Groot
Subject: Re: First image posting
Date: 3 May 2021 07:33:04
Message: <608fdf70$1@news.povray.org>
Op 3-5-2021 om 11:11 schreef jr:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> Op 03/05/2021 om 09:19 schreef jr:
>>> ...
>> I conclude from that [thread], that aa is the ray-tracing answer to mipmapping,
>> and I guess that my initial suggestion of stochastic aa is the correct one.
> 
> taking the 'El Capitan' cliff face as an example, say I want to render two
> images: object near base of, and object some distance from.  then I need to
> choose a scale for the texture(s)?  I think that I (as in "numpty" etc) would
> benefit from having some row/col table, in the documentation and or as array, of
> all parameters involved ("lambda", "octave", such) by scale/suggested distance
> (in POV-units?).  (and perhaps a macro which expands to the texture at the given
> scale/index)  (just thinking aloud :-))
> 
Yes, I guess that is the crucial point here. Otoh, It can also be solved 
by using a much simpler texture for the background, involving the same 
colour_map scaled down, and without all the fancy stuff...

> 
> regards, jr.
> 
> btw, re "graveyards".  had to put on an anorak, even for a cursory read.  :-)
> found out that what I associate with "granite" really is "dolerite".  thanks.
> 
<grin> They are often mixed-up.

-- 
Thomas


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From: Thomas de Groot
Subject: Re: First image posting
Date: 3 May 2021 07:34:01
Message: <608fdfa9$1@news.povray.org>
Op 3-5-2021 om 12:34 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
> what is (at least for me) is how to chose the right texture
>> for each render or location in the scene (for instance the background of
>> a chequered plane smoothly grading into the foreground).
> 
> I guess you could have a macro generate the texture, and have an AutoScale
> argument.  The distance from the camera to the closest object (user-supplied
> value) could be used to set the scale.  Might need to set a pov unit = real
> world measurement ratio and base everything off that.
> 
> 
Yes something like that is needed anyway.

-- 
Thomas


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From: s day
Subject: Re: First image posting
Date: 7 May 2021 07:35:00
Message: <web.6095251ef7d27fee8de81c16a8f0b95@news.povray.org>
Some decent modelling, areas I would look at to improve are:

Bricks look too uniform especially on the floor and garden wall.
The join of the garden wall to the house looks odd, particularly on the left
where it is well lit.

Some of the textures need more work, particurarly on the floor, think of
layering some dirt over the top and when doing that try to add dirt in realistic
areas (darker in the corners/nearer the ground etc).
I can't say exactly what it is but the lighting looks odd maybe better radiosity
settings.

The roof looks great and the modelling/texture on the bucket in the well is very
good.

I tend to always add focal blur (not that I have done much with Pov for a
while).

Sean


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From: Leroy
Subject: Re: First image posting
Date: 8 May 2021 13:30:00
Message: <web.6096ca23f7d27fef78c0a28f712fc00@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>
> > Yes, that is certainly true indeed. Try to find the balance.
> > Sometimes/often, stochastic anti-aliasing helps for the grainy distance
> > mess.
>
> Presumably, this is what all this "mip-mapping" business is about.   Has anyone
> ever tried to emulate that process, that we know of?

I have done "mip-mapping" but that was for Quake2 video game graphics, using POV
to make them. I might add badly. The trouble is selecting what to drop and what
to keep. When working on Quake2 the first mip is half the size of the main
texture and the next is half the size of first mip and so on. I guess that if
you wanted to use a mip type texture in POV that the texture would have to be
scaled up and simple-fided for the distance from the camera. A tough feat.

Have Fun!


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From: Chris R
Subject: Re: First image posting
Date: 4 Jun 2021 16:25:00
Message: <web.60ba8b10f7d27fe2a4268365cc1b6e@news.povray.org>
"s.day" <s.d### [at] uelacuk> wrote:
> Some decent modelling, areas I would look at to improve are:
>
> Bricks look too uniform especially on the floor and garden wall.
> The join of the garden wall to the house looks odd, particularly on the left
> where it is well lit.
>
> Some of the textures need more work, particurarly on the floor, think of
> layering some dirt over the top and when doing that try to add dirt in realistic
> areas (darker in the corners/nearer the ground etc).
> I can't say exactly what it is but the lighting looks odd maybe better radiosity
> settings.
>
> The roof looks great and the modelling/texture on the bucket in the well is very
> good.
>
> I tend to always add focal blur (not that I have done much with Pov for a
> while).
>
> Sean

Thanks for the comments!

The garden wall is an isosurface that uses a brick pigment pattern to add the
individual blocks.  I had added turbulence to the brick pattern so the edges of
the blocks are uneven, but the limitation is that all of the blocks are
basically the same size and offset by 1/2.  I could redo it and randomly
generate blocks with a more complicated layout.

At one point I had added a sand layer to the floor of the well/garden area.  I
had tried to add some mossy coloring as well, but I didn't like how green
everything got, so I took it out and didn't go back again.  The blocks for the
floor could have more variability in size and shape as well.

I have only done a little work with radiosity, especially in outdoor scenes, so
I'm not surprised there may be issues.

I think if I were doing a view of this scene that was more zoomed in on one of
the elements I'd be more inclined to invest the time into adding focal blur.  As
an overview shot, if I were using my camera, I'd be using f6 or more, so I
didn't bother.  A closeup of the bucket dripping water would be a good time to
break out the f2.8 or f1.4 lens, though.


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