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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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Tek wrote:
> 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 :)
>
>
It is getting really good. Two comments:
- There is not much snow/ice in the picture relative to the fires
- The sea is too smooth
and a suggestion: put some some ice on the sea, that'll solve both
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Tek
I love the shift in the plume/wind effect.
It occurs to me that this is shallow and possibly tidal water,
Given that, your underwater lava could be be a continuation of the stream
from the peak being quenched by the icy water.
You may consider a tube/shell for the underwater stuff with a bubbling out
at the hot front?
How will you manage vigorous boiling? I can't wait.
D
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"Christoph Hormann" <chr### [at] gmx de> wrote in message
news:drv7jv$jc0$1@chho.imagico.de...
> Note these are aspects to improve realism - you might not intend to make
> this most realistic of course.
Well I want it fairly realistic, the composition's very artificial so I want
to balance that with some realism.
> The Lava: it should always flow downhill - in your case it goes uphill in
> some places.
No it doesn't! The code that places the rivers of lava can only flow
downwards, also looking at the picture I can't see anywhere that it appears
to move upwards. If it looks like that to you then it's probably an illusion
of perspective: the camera is lower than the volcano so if the lava travels
almost flat towards us it will seem to move up.
Oh, and the underwater lava travels in a completely horizontal direction,
which isn't realistic but is fine for this image.
> Also it is somewhat too dark for smoothly flowing lava (the dark red one
> at the water edge would hardly flow any more). It is reasonable to make
> the lava as bright as the flying one at the top of the mountain.
Well I know I've seen footage of lava flowing where the surface was almost
black, but with patches of red in it. This is the effect I was trying to
achieve, but I don't think it's there yet.
> The mountains: Like in terragen images you have a fine structured visible
> surface contrasting with smooth edges. This probably is a result of using
> bump mapping on a relatively low detail terrain. This makes it look a bit
> like a theatre mountain made of painted styrofoam.
You're right the shape doesn't look rocky enough, I'll try adjusting the
material and isosurface (there's no bump mapping).
> The 'pyrotechnical effects' are great but does the dust cast shadows on
> itself and the mountains?
Yes it does, though at the moment that's not obvious. I'll work on that when
I get round to it.
--
Tek
http://evilsuperbrain.com
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That's pretty much exactly what it does! I have a macro already, the only
limitation of it is that it doesn't look for the steepest slope, just any
downward slope. Nonetheless this does mean that it definitely doesn't flow
up hill at any point.
Could someone point out the bits where it looks wrong? Honestly I can't see
it!
--
Tek
http://evilsuperbrain.com
"David El Tom" <dav### [at] t-onlinede> wrote in message
news:43e466a7@news.povray.org...
> 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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The smoke's ridiculously simple, it's just a spherical density function with
turbulence, then I messed with the lambda and omega of the turbulence and
rotated the effect to line up one of the sticking out bits with the top of
the volcano.
But I will provide source, it's all in 1 pov file at the moment so I have no
excuse not to give the source.
--
Tek
http://evilsuperbrain.com
"s.day" <s.d### [at] uelacuk> wrote in message
news:web.43e32370f33fba362a868be00@news.povray.org...
> This is starting to look really good especially the smoke/fire effect. I
> was
> thinking of doing a snow covered volcano scene myself for this round of
> IRTC but am glad I didn't as my attempts were nowhere near as good as
> this.
> Congrats on winning the round before last BTW that was a great image. As
> this is still WIP I guess you may be planning to change the following (and
> I think these may have been mentioned in previous posts) but I think the
> rocks at the front need to look a bit more like they are glowing and they
> would be having an effect on the water, the lava flow at the bottom of the
> volcano would probably not be so close to the snow (without melting it). I
> also agree with you that the image needs a bit more colour (not sure where
> or how this can be added though)
>
> I hope you post the source with this one as I would like to steal (I mean
> learn from..) your smoke effect.
>
> Great work.
>
> Sean
>
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Yay! I think you're the first person to agree with me about the above/below
water split :)
--
Tek
http://evilsuperbrain.com
"Bill Pragnell" <bil### [at] hotmailcom> wrote in message
news:web.43e34b63f33fba36731f01d10@news.povray.org...
> "Tek" <tek### [at] evilsuperbraincom> wrote:
>> -colours: it's all gone a bit grey in this version, I want to get some
>> black
>> in the smoke and volcanic rocks.
> I quite like the grey, at least for the rocks - looks more volcanic.
>
> I can only think of two other comments, although they're quite minor.
> Firstly, I think the lava fountain is a bit regular - too much like a
> point
> source; maybe having several sources together would give it a little more
> volume. Secondly, the flowing lava (and the underwater lava) should
> perhaps
> glow a little brighter (although maybe the brightness of the river should
> decrease with distance?).
>
> Fantastic looking image, though, especially the above/below water split -
> this is going to be a classic!
>
> Bill
>
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I agree with all of that apart from the shapes, which really do look like
seperate blobs:
http://images.google.com/images?sourceid=navclient-ff&ie=UTF-8&rls=GGGL,GGGL:2005-09,GGGL:en&q=pillow+lava
I tried a more interconnected one (it's all a blob object so I can just
adjust the strength to smooth it out), but it looked less like the reference
photos.
--
Tek
http://evilsuperbrain.com
"Thomas de Groot" <t.d### [at] internlnet> wrote in message
news:43e34c69@news.povray.org...
> Great improvements!
> Something that bothers me a little: the lava underwater looks a little bit
> too much like separate blobs of matter. I think they should be more
> interconnected, forming a bumpy flow over overlapping blobs, but
> well-welded
> together within the flow. A few more bright burstings, more in the
> background would also improve that part of the scene, while increasing
> perhaps somewhat the murkiness of the water.
>
> Thomas
>
>
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Well I tried some fog and it destroyed the contrast in the upper part of the
image, the effect is still there but it's turned down so low it's hardly
visible. I agree though, I need more atmospheric effects between the camera
and the volcano, I'm hoping that when I add steam from all the
lava-snow-water interactions it will look right.
BTW thanks for the snow-lava reference, I had failed to find any. I assumed
that snow couldn't get that close to lava so I was going to completely
remove snow in the surrounding area, but now I think I might keep it fairly
close but with lots of melting/steaming effects... Or I'll hide it all
behind a plume of steam where it pours into the sea...
--
Tek
http://evilsuperbrain.com
"Kevin Wampler" <wampler+pov### [at] uwashingtonedu> wrote in message
news:43e39a72$1@news.povray.org...
> This is coming along quite nicely! Other than things that other people
> have mentioned, there are a couple of things that strike me. First I
> would guess that there's be some snow melt bordering the lava flow.
> Currently it seems like the lava borders the snow directly and I think
> this is what makes the lava flow look "pasted on" to me. I looked for an
> image to confirm this, but this was the best I found, and it's not a
> particularly clear picture of it:
>
> http://www.spring.net/marci/Public/Hawaii/LavaOnSnow.jpg
>
> It's also possible that the scene could benefit from some haze. Other
> than the smoke plume itself, the air is very clear. Part of this I
> imagine is because it gives a really nice contrast in the upper part of
> the image, but perhaps some small amount of haze could still help without
> destroying this effect.
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Well it's top is 1000m above the water level, I suspect it's just the
isosurface which looks a little too rounded.
--
Tek
http://evilsuperbrain.com
"Alain" <ele### [at] netscapenet> wrote in message
news:43e3f609$1@news.povray.org...
> 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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