"Tek" <tek### [at] evilsuperbraincom> wrote in message 
news:43e300e2@news.povray.org...
>I now have some proper smoke and underwater lava!
>
> The only things I can see that need more work now are:
> -steam: many people suggested various points for steam to be appearing, 
> and I totally agree.
> -colours: it's all gone a bit grey in this version, I want to get some 
> black in the smoke and volcanic rocks.
> -more colours!: that water just looks wrong IMO, should be very cloudy, 
> darker, less green, and with steam bubbling round the lava.
> -background: those conical mountains will change into realistic ones 
> eventually I promise, and the sky colour's maybe too bright
>
> But I'm sure you folks can think of other things to improve!
>
> Your comments thus far have helped immensely! So keep them coming :)

      Well, to me Tek, it seems like it's a 'small' volcano. I don't know 
whether I'm right or wrong with this, and I wouldn't know how to rectify it 
in this scene, but I thought volcanoes were usually *big*? I don't see a 
sense of scale here.

    Otherwise, really good improvements imo. Should make for a *very* good 
final image.

    Me? I haven't even started yet...  :/

       ~Steve~


>
> -- 
> Tek
> http://evilsuperbrain.com
>
>
>

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"Christoph Hormann" <chr### [at] gmxde> wrote in message 
news:drv7jv$jc0$1@chho.imagico.de...


    I'm having a job to see where it's flowing uphill?

      ~Steve~



> Christoph

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>>But due to the heat you get some kind of striation (Schlierenbildung ???), 
>>meaning the large temperature gradient causes a field of water with 
>>variable IOR surrounding the lava.
> 
> 
> Well heat ripples aren't so vital, unless it's an animation. But anyway it's 
> a good idea I'll see how it looks if I cheat with a simple change in IOR 
> along a bumpy surface.

Yeah - since you're not animating it, you could perhaps get away with a 
simple plane in front of the hot parts with weird normals to make it 
look all blurry and warped. Would only look correct from one direction - 
but that's all you need.

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I'm liking it. The sky *is* too bright. And that smoke cloud should have 
big black parts to it. Would also be cool (haha!) if the flying boulders 
would illuminate the smoke cloud - but I have no idea how in hell you do 
that without having to wait several epocs for POV-Ray to draw it! :-/

IME, the laval should be brighter. Sometimes laval flows develop of sort 
of dark bit along the middle and the edges. The bits round the edges 
stay stationary, and the bits on top move with the flow. This is why 
they don't join; the flow rips them apart.

Of course, all of that depends on how hot the lava is, how viscous it 
is, how fast it's moving, etc etc etc, so...

I'm liking what's happening under water. Perhaps the water should be 
slightly more murky, I'm not sure. (I really like the sea floor, so it 
would be a shame to completely obscure it!) The glowing lava should 
perhaps slightly illuminate the sea floor - but that would surely demand 
radiosity... (Hope you have a nice render farm!)

Distribution of flying rock is perhaps a touch too uniform. (All the 
arcs seem to lead back to a single point. Maybe make the launch 
direction slightly random...)

No further comments, really. Looking good!

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>    I'm having a job to see where it's flowing uphill?

Look at the central lava river coming down... It seems to dissapear into 
some kind of "dip" in the surface, yet continues flowing over the rip of 
that dip (hence "uphill").

Of course, liquid rock is hot. And liquid. But it's still heavy. I 
imagine lava has quite a lot of momentum if it's moving fast... it's 
just a question of how much momentum exactly.

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St. wrote:
> 
>    I'm having a job to see where it's flowing uphill?
> 

When i say "it should always flow downhill" this does not necessarily 
mean it flows uphill in the image (although i am sure it does in some 
places).  It is simply not taking the downhill direction everywhere 
(i.e. the *steepest* direction going down).

Christoph

-- 
POV-Ray tutorials, include files, Landscape of the week:
http://www.imagico.de/ (Last updated 31 Oct. 2005)
MegaPOV with mechanics simulation: http://megapov.inetart.net/

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>>    I'm having a job to see where it's flowing uphill?
>>
> 
> When i say "it should always flow downhill" this does not necessarily 
> mean it flows uphill in the image (although i am sure it does in some 
> places).  It is simply not taking the downhill direction everywhere 
> (i.e. the *steepest* direction going down).

Momentum and viscosity - but yeah, I see what you're saying.

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> Underwater has come a long way but it looks too quiet, almost tranquil.
> Now I don't get a sense of the brute forces that are at work there. (but
> don't ask me how to do that :) )

The underwater part is a major, major, improvement. :-)

Suggestion: Can you make it look like it flows a little more as it cools?

I don't have any pics in front of me, but I've seen footage of underwater
volcanos that came up to a point like a terrestrial volcano, and the lava
kind of oozed down the sides. The layer of lava exposed to water cools
pretty quickly, but the inside stays molten long enough for the mass to
slide around a little.

Maybe you could try applying your fantastic texture to blob objects. :-)

William

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St. nous apporta ses lumieres en ce 03/02/2006 14:03:
> 
> "Tek" <tek### [at] evilsuperbraincom> wrote in message 
> news:43e300e2@news.povray.org...
> 
>> I now have some proper smoke and underwater lava!
>>
>> The only things I can see that need more work now are:
>> -steam: many people suggested various points for steam to be 
>> appearing, and I totally agree.
>> -colours: it's all gone a bit grey in this version, I want to get some 
>> black in the smoke and volcanic rocks.
>> -more colours!: that water just looks wrong IMO, should be very 
>> cloudy, darker, less green, and with steam bubbling round the lava.
>> -background: those conical mountains will change into realistic ones 
>> eventually I promise, and the sky colour's maybe too bright
>>
>> But I'm sure you folks can think of other things to improve!
>>
>> Your comments thus far have helped immensely! So keep them coming :)
> 
> 
>      Well, to me Tek, it seems like it's a 'small' volcano. I don't know 
> whether I'm right or wrong with this, and I wouldn't know how to rectify 
> it in this scene, but I thought volcanoes were usually *big*? I don't 
> see a sense of scale here.
> 
>    Otherwise, really good improvements imo. Should make for a *very* 
> good final image.
> 
>    Me? I haven't even started yet...  :/
> 
>       ~Steve~
> 
> 
>>
>> -- 
>> Tek
>> http://evilsuperbrain.com
>>
>>
>>
> 
A volcano start small, nothing more than a bump, and grow larger the longer it stays
active. The 
large ones you are used to took millenia to reach their actual dimentions. This one
may be *only* 2 
or 3 centurys old...

-- 
Alain
-------------------------------------------------
A day without sunshine is like, night

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Christoph Hormann wrote:
> St. wrote:
>>
>>    I'm having a job to see where it's flowing uphill?
>>
> 
> When i say "it should always flow downhill" this does not necessarily 
> mean it flows uphill in the image (although i am sure it does in some 
> places).  It is simply not taking the downhill direction everywhere 
> (i.e. the *steepest* direction going down).
> 
> Christoph
> 

should be not to hard to code a macro to trace a path with steepest descent.

(some kind of local monte carlo approach, similar to the methods used to find 
local minima of multi-dimensional hypersurfaces)

  - store the altitude of the current position
  - step forward
  - shoot rays in random fashion around the new position and trace the altitudes 
(the more you shoot the greater is the possibility to find the local steepest 
descent for this point)
  - compare thoose with the stored one and alter direction to the one with 
biggest difference
  - store this point as new position.

if you would store the gradient at each point you could use it reciprocal factor 
for the broadness of the lava flow, as it shoud get thighter if it flows faster 
and broader if it flows slower (constant flow rate).

another possibilty is to use the analytical derivative of the function you use 
for the volcano surface.

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