Hi, back to basics.

Lathes and procedural textures/materials

1. I have no idea yet how to mould a handle and a spout
onto the teapot, but I hope I'll figure something out.

2. There's something not quite right about the china, too
"soft"? but I don't know how to improve it.

3. I'm quite happy with the wood texture, but I could take
it further.

4. I realise the bubble in the tea looks fake, I'll work more
on that.

My big question is, I'd like to get some turbulence and
variation in the colour of the tea, especially around the
tea leaves, due to convection, but again I'm at a loss.

I'd appreciate any helpful criticisms, I can post source
for the textures if anyone's interested.

-- 
Bill Hails
http://thyme.homelinux.net/

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Attachments:
Download 'tea.jpg' (128 KB)

Preview of image 'tea.jpg'

> 1. I have no idea yet how to mould a handle and a spout
> onto the teapot, but I hope I'll figure something out.
I'm a little teapot, short and stout,
Here's my... here's my... erm...

Good start. I like your approach: it is elegant and clean.

Daniel
-- 
Now  as he walked by the sea  of Galilee,  he saw  Simon and Andrew  his
brother casting a spam into the net:  for they were phishers.  And Jesus
said unto them, Come ye after me, and I will make you to become phishers
of men.  And  straightway  they forsook  their  nets,  and followed him.

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Quite pleasing!.

"Bill Hails" <bil### [at] europeyahoo-inccom> wrote in message 
news:4282738c@news.povray.org...
> Hi, back to basics.
>
> Lathes and procedural textures/materials
>
> 1. I have no idea yet how to mould a handle and a spout
> onto the teapot, but I hope I'll figure something out.
>
> 2. There's something not quite right about the china, too
> "soft"? but I don't know how to improve it.
Your china is porcelain. Heavy duty cafeteria porcelain. Fine bone china is 
whiter, thinner and somewhat translucent.
Of course you might have something else in mind, like "the Utah teapot" 
http://www.sjbaker.org/teapot/



>
> 3. I'm quite happy with the wood texture, but I could take
> it further.
Nice.

>
> 4. I realise the bubble in the tea looks fake, I'll work more
> on that.
What bubble? ior=1?
The meniscus is nicely modelled.

>
> My big question is, I'd like to get some turbulence and
> variation in the colour of the tea, especially around the
> tea leaves, due to convection, but again I'm at a loss.
Turbulence. Do you mean something like a fractal volume with a lower ior?
Color variation. You're looking to see a pigment density gradient in the 
vicinity of the leaves?
What kind of tea is that pink?
Steam/media above the surface?
Apart from the edges where there is a clear color intensity gradient, the 
bulk of the tea has a very uniform color.
With a light absorbing medium the intensityyou expect the Beer-Lambert law 
to operate
A=ECd where A=-log10(transmission), E is the extinction coefficient, C is 
the concentration of the absorbing solute and d is the length of the optical 
path.
Given all that, the tea at the bottom of the cup should be darker.

Looking forward to another cup...

DLM


>
> I'd appreciate any helpful criticisms, I can post source
> for the textures if anyone's interested.
>
> -- 
> Bill Hails
> http://thyme.homelinux.net/

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dlm wrote:

> Quite pleasing!.

Thanks!

> "Bill Hails" <bil### [at] europeyahoo-inccom> wrote in message
> news:4282738c@news.povray.org...
>> Hi, back to basics.
>>
>> Lathes and procedural textures/materials
>>
>> 1. I have no idea yet how to mould a handle and a spout
>> onto the teapot, but I hope I'll figure something out.
>>
>> 2. There's something not quite right about the china, too
>> "soft"? but I don't know how to improve it.
> Your china is porcelain. Heavy duty cafeteria porcelain. Fine bone china
> is whiter, thinner and somewhat translucent.

I should have said porcelain, sorry. I still don't think it looks quite
right, something makes it appear like I'm using focal blur when I'm not,
esp. the top right cup.

> Of course you might have something else in mind, like "the Utah teapot"
> http://www.sjbaker.org/teapot/

I knew it existed, thanks for the link. I did say "back to basics"
so the connection had occurred to me, However I'm lucky enough to
work very near London's Chinatown, and many of the cafe's serve
tea in these elegant tea services, so I bought one from a local
Chinese shop and brought it home to model it (and enjoy the tea).

> 
> 
>>
>> 3. I'm quite happy with the wood texture, but I could take
>> it further.
> Nice.

I was thinking some localised abrasion might help.

>>
>> 4. I realise the bubble in the tea looks fake, I'll work more
>> on that.
> What bubble? ior=1?
> The meniscus is nicely modelled.

bubble is difference { union { object { Tea } sphere } sphere }
meniscus is difference { object { Tea } union { cylinder torus scale <R, 1, 
R> } }

>>
>> My big question is, I'd like to get some turbulence and
>> variation in the colour of the tea, especially around the
>> tea leaves, due to convection, but again I'm at a loss.
> Turbulence. Do you mean something like a fractal volume with a lower ior?

yeah, f_noise3d or f_ridged_mf might do it, if I subtract lots of it
from a sphere around the tealeaves.

> Color variation. You're looking to see a pigment density gradient in the
> vicinity of the leaves?

more of a "fire" or "smoke" effect as the pigment seeps out of the leaves.
I have noticed the effect while drinking tea and modelling :-)

> What kind of tea is that pink?

It looked pretty close to the tea I was drinking at the time.

> Steam/media above the surface?

maybe, but every element I add is another element I have to get right,
hopefully the turbulence in the liquid will be enough to suggest heat.

> Apart from the edges where there is a clear color intensity gradient, the
> bulk of the tea has a very uniform color.
> With a light absorbing medium the intensityyou expect the Beer-Lambert law
> to operate
> A=ECd where A=-log10(transmission), E is the extinction coefficient, C is
> the concentration of the absorbing solute and d is the length of the
> optical path.
> Given all that, the tea at the bottom of the cup should be darker.

I just took it from the manual:

"If you set fade_power in the interior of an object at 1000 or above, a 
realistic exponential attenuation function will be used:

 
  Attenuation = exp(-depth/fade_dist)"
 
> Looking forward to another cup...

Thanks very much for your comments.

> 
> DLM
> 
> 
>>
>> I'd appreciate any helpful criticisms, I can post source
>> for the textures if anyone's interested.
>>
>> --
>> Bill Hails
>> http://thyme.homelinux.net/

-- 
Bill Hails
http://thyme.homelinux.net/

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Nice pic, I'd love to see it when it's further along.  A question about the
tea: did you use interior scattering media to give it the colour?  If not,
that might give you better light fading within the liquid, possibly more
realistic than using fade_distance etc.  I only mention it because I was
just now playing around with a murky-looking sea effect, and with less
'murk' it might have the sort of properties you're after.  I'll post
something up when I get it right.

L
-

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Loki wrote:

> Nice pic, I'd love to see it when it's further along.  A question about
> the
> tea: did you use interior scattering media to give it the colour?  If not,
> that might give you better light fading within the liquid, possibly more
> realistic than using fade_distance etc.  I only mention it because I was
> just now playing around with a murky-looking sea effect, and with less
> 'murk' it might have the sort of properties you're after.  I'll post
> something up when I get it right.
> 
> L
> -

No, no media, The tea is transparent, I thought media would cloud it
which wouldn't be right. I was hoping that fade_power 1001 would
do the trick, but apparently not :-(

-- 
Bill Hails
http://thyme.homelinux.net/

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> No, no media, The tea is transparent, I thought media would cloud it
> which wouldn't be right. I was hoping that fade_power 1001 would
> do the trick, but apparently not :-(
>
> --
> Bill Hails
> http://thyme.homelinux.net/

It wouldn't have to be too cloudy - I was thinking of an almost
imperceptible amount.  Thing is, with a scattering media you have more
control over the final outcome because you can change colour/extinction/etc
independently, whereas fade_power seems a little limited in some cases.  I
was thinking maybe a tiny bit of media might help.  But then, maybe not!

L
-

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Excellent start. I look forward to seeing the progress on your scene.

The porcelain looks very good, thought it gives the impression of being 
cheap cafeteria ceramic, as somebody has already pointed out. However, 
it imitates that material very well! With some tweaking I'm sure you'll 
get the right texture.

Fernando.

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Bill Hails nous apporta ses lumieres en ce 2005-05-11 23:05:
> Hi, back to basics.
> 
> Lathes and procedural textures/materials
> 
> 1. I have no idea yet how to mould a handle and a spout
> onto the teapot, but I hope I'll figure something out.
You can try: sphere_sweep, spline + blob, isosurface, torus.
> 
> 
> 4. I realise the bubble in the tea looks fake, I'll work more
> on that.
The buble should protude a little bit in the meniscus, ie. push the near part a small
bit upward. 
You may need to use a blob or an isosurface for the whole thea.

> 
> My big question is, I'd like to get some turbulence and
> variation in the colour of the tea, especially around the
> tea leaves, due to convection, but again I'm at a loss.
Using some media will enable to modulate the density around the leaves. You can then
add some 
turbulence to that variable density. That combined with fade_color fade_distance can
get prety 
realistic.
> 
> I'd appreciate any helpful criticisms, I can post source
> for the textures if anyone's interested.
> 
> 
> 
> ------------------------------------------------------------------------
> 

Alain

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Loki wrote:

> 
>> No, no media, The tea is transparent, I thought media would cloud it
>> which wouldn't be right. I was hoping that fade_power 1001 would
>> do the trick, but apparently not :-(
>>
>> --
>> Bill Hails
>> http://thyme.homelinux.net/
> 
> It wouldn't have to be too cloudy - I was thinking of an almost
> imperceptible amount.  Thing is, with a scattering media you have more
> control over the final outcome because you can change
> colour/extinction/etc
> independently, whereas fade_power seems a little limited in some cases.  I
> was thinking maybe a tiny bit of media might help.  But then, maybe not!
> 
> L
> -

I'm going to try media, thanks.

-- 
Bill Hails
http://thyme.homelinux.net/

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