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El 05/04/16 a las 12:11, Jaime Vives Piqueres escribió:
> ... still needs work.
Well, the proximity pattern is still not what I really need, but gets
close. Unfortunately it really makes the render much slower (x4)...
luckly I'm using a mesh: with an isosurface this would have taken almost
2/3 days.
--
jaime
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Attachments:
Download 'ocean-15e.jpg' (101 KB)
Preview of image 'ocean-15e.jpg'
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On 7-4-2016 9:17, Jaime Vives Piqueres wrote:
> El 05/04/16 a las 12:11, Jaime Vives Piqueres escribió:
>> ... still needs work.
>
> Well, the proximity pattern is still not what I really need, but gets
> close. Unfortunately it really makes the render much slower (x4)...
> luckly I'm using a mesh: with an isosurface this would have taken almost
> 2/3 days.
>
This is very close indeed. Less convincing foam close up but in the
distance it looks very good.
--
Thomas
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On 4/7/2016 8:17 AM, Jaime Vives Piqueres wrote:
> El 05/04/16 a las 12:11, Jaime Vives Piqueres escribió:
>> ... still needs work.
>
> Well, the proximity pattern is still not what I really need, but gets
> close. Unfortunately it really makes the render much slower (x4)...
> luckly I'm using a mesh: with an isosurface this would have taken almost
> 2/3 days.
>
That looks good to me.
Sea state 5 or 6, I would guess.
In 2009 Edouard Poor created DF3 proximity pattern macros.
That might be worth a try.
--
Regards
Stephen
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On 7-4-2016 10:08, Stephen wrote:
> On 4/7/2016 8:17 AM, Jaime Vives Piqueres wrote:
>> El 05/04/16 a las 12:11, Jaime Vives Piqueres escribió:
>>> ... still needs work.
>>
>> Well, the proximity pattern is still not what I really need, but gets
>> close. Unfortunately it really makes the render much slower (x4)...
>> luckly I'm using a mesh: with an isosurface this would have taken almost
>> 2/3 days.
>>
>
> That looks good to me.
> Sea state 5 or 6, I would guess.
> In 2009 Edouard Poor created DF3 proximity pattern macros.
> That might be worth a try.
>
>
I was going to suggest Edouard's macros too. I prefer them to Sam's and
believe them to be faster. Advantage is that the pattern is calculated
and saved to file before render.
--
Thomas
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Am 07.04.2016 um 09:17 schrieb Jaime Vives Piqueres:
> El 05/04/16 a las 12:11, Jaime Vives Piqueres escribió:
>> ... still needs work.
>
> Well, the proximity pattern is still not what I really need, but gets
> close. Unfortunately it really makes the render much slower (x4)...
> luckly I'm using a mesh: with an isosurface this would have taken almost
> 2/3 days.
I'm wondering: Presuming the foam is a texture (rather than a media
effect), shouldn't a slope pattern do the job?
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El 07/04/16 a las 09:58, Thomas de Groot escribió:
> This is very close indeed. Less convincing foam close up but in the
> distance it looks very good.
That's another matter... the foam texture is not very good. I find it
very difficult to get a convincing one.
--
jaime
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El 07/04/16 a las 10:08, Stephen escribió:
> That looks good to me. Sea state 5 or 6, I would guess.
Thanks!
> In 2009 Edouard Poor created DF3 proximity pattern macros. That might
> be worth a try.
Thanks, I will try... also the proximity pattern included on hgpovray
(I just found about it).
--
jaime
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El 07/04/16 a las 13:35, clipka escribió:
> I'm wondering: Presuming the foam is a texture (rather than a media
> effect), shouldn't a slope pattern do the job?
>
Yes, it is a texture (well, a pattern for the combined water/foam
texture map). And yes, that's what I thought at first, so I tried a
slope y with altitude, but didn't work very well... maybe my fault at
implementing it, but then I thought about the proximity pattern thing,
so I abandoned the slope approach.
--
jaime
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Am 07.04.2016 um 13:47 schrieb Jaime Vives Piqueres:
> El 07/04/16 a las 13:35, clipka escribió:
>> I'm wondering: Presuming the foam is a texture (rather than a media
>> effect), shouldn't a slope pattern do the job?
>>
>
> Yes, it is a texture (well, a pattern for the combined water/foam
> texture map). And yes, that's what I thought at first, so I tried a
> slope y with altitude, but didn't work very well... maybe my fault at
> implementing it, but then I thought about the proximity pattern thing,
> so I abandoned the slope approach.
I wouldn't use altitude, just the plain slope.
Given that the slope pattern is a lot faster than any proximity pattern,
I think it should be worth another try.
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El 07/04/16 a las 15:52, clipka escribió:
> I wouldn't use altitude, just the plain slope.
>
> Given that the slope pattern is a lot faster than any proximity
> pattern, I think it should be worth another try.
>
But just plain "slope y" shows foam also on "valley" parts of the
surface, not only on the crests. Or are you suggestion another approach?
--
jaime
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Am 07.04.2016 um 16:26 schrieb Jaime Vives Piqueres:
> El 07/04/16 a las 15:52, clipka escribió:
>> I wouldn't use altitude, just the plain slope.
>>
>> Given that the slope pattern is a lot faster than any proximity
>> pattern, I think it should be worth another try.
>>
>
> But just plain "slope y" shows foam also on "valley" parts of the
> surface, not only on the crests. Or are you suggestion another approach?
From what I see the waves aren't sinusoidal, but have "sharp" peaks, so
a high slope should be the proper indicator.
Then again, I must concede that this idea crumbles if the peaks aren't
perfectly sharp after all.
Let's take a step backward:
What you want is foam at the crests, i.e. near local maxima.
Local maxima can be identified by a zero 1st derivative (aka slope) and
negative 2nd derivative (aka curvature).
It should be possible to analyze the f_ridged_mf() function in order to
construct the 1st and 2nd derivative functions, and use the resulting
functions as a basis for a foam pattern. (If you want to avoid function
analysis, you could still design functions for the slope and curvature
that effectively take samples from the original function.)
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El 07/04/16 a las 16:54, clipka escribió:
> Then again, I must concede that this idea crumbles if the peaks
> aren't perfectly sharp after all.
Well, the function heighfield I'm using is surely having flat
triangles there. For perfectly sharp crests I guess I would have to use
crazy resolutions.
> Let's take a step backward:
>
> What you want is foam at the crests, i.e. near local maxima.
>
> Local maxima can be identified by a zero 1st derivative (aka slope)
> and negative 2nd derivative (aka curvature).
>
> It should be possible to analyze the f_ridged_mf() function in order
> to construct the 1st and 2nd derivative functions, and use the
> resulting functions as a basis for a foam pattern. (If you want to
> avoid function analysis, you could still design functions for the
> slope and curvature that effectively take samples from the original
> function.)
>
:O ...that's a too advanced approach for me: I barely passed maths at
school.
--
jaime
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Jaime Vives Piqueres <jai### [at] ignorancia org> wrote:
> El 07/04/16 a las 16:54, clipka escribió:
> > Then again, I must concede that this idea crumbles if the peaks
> > aren't perfectly sharp after all.
>
> Well, the function heighfield I'm using is surely having flat
> triangles there. For perfectly sharp crests I guess I would have to use
> crazy resolutions.
If you test the function instead of the height field, that won't be a problem.
> > Let's take a step backward:
> >
> > What you want is foam at the crests, i.e. near local maxima.
> >
> > Local maxima can be identified by a zero 1st derivative (aka slope)
> > and negative 2nd derivative (aka curvature).
> >
> > It should be possible to analyze the f_ridged_mf() function in order
> > to construct the 1st and 2nd derivative functions, and use the
> > resulting functions as a basis for a foam pattern. (If you want to
> > avoid function analysis, you could still design functions for the
> > slope and curvature that effectively take samples from the original
> > function.)
> >
>
> :O ...that's a too advanced approach for me: I barely passed maths at
> school.
My instinct would be to avoid the analysis approach, and do sampling on the
original function. That doesn't take a lot of sophisticated math. I can't even
remember the chain rule without looking it up (and the last time I did so was,
like, 2005), but I have used sampling to estimate normals on a form based on
parametric functions. I did this for the smooth triangles of the elliptical
toroids in RoundEdge. Normals, of course, can be easily converted to slopes.
Sampling won't get you the 2nd derivative, but it will tell you whether it's
positive or negative, which is enough for clipka's plan.
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El 08/04/16 a las 06:45, Cousin Ricky escribió:
> My instinct would be to avoid the analysis approach, and do sampling
> on the original function. That doesn't take a lot of sophisticated
> math. I can't even remember the chain rule without looking it up
> (and the last time I did so was, like, 2005), but I have used
> sampling to estimate normals on a form based on parametric functions.
> I did this for the smooth triangles of the elliptical toroids in
> RoundEdge. Normals, of course, can be easily converted to slopes.
>
I'm still trying to grasp the concept of "sampling a function"... how
I would do that? With another function? If someone can please post a
simple example...
--
jaime
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Am 08.04.2016 um 09:49 schrieb Jaime Vives Piqueres:
> El 08/04/16 a las 06:45, Cousin Ricky escribió:
>> My instinct would be to avoid the analysis approach, and do sampling
>> on the original function. That doesn't take a lot of sophisticated
>> math. I can't even remember the chain rule without looking it up
>> (and the last time I did so was, like, 2005), but I have used
>> sampling to estimate normals on a form based on parametric functions.
>> I did this for the smooth triangles of the elliptical toroids in
>> RoundEdge. Normals, of course, can be easily converted to slopes.
>>
>
> I'm still trying to grasp the concept of "sampling a function"... how
> I would do that? With another function? If someone can please post a
> simple example...
// Base function
#declare Fn = function(x,y) { /* whatever */ }
#declare EPSILON = 1e-6;
// Approximate first derivatives along the x and y axes
#declare Fn1X = function(x,y)
{ (Fn(x+EPSILON,y)-Fn(x-EPSILON,y))/EPSILON }
#declare Fn1Y = function(x,y)
{ (Fn(x,y+EPSILON)-Fn(x,y-EPSILON))/EPSILON }
// Approximate second derivatives along the x and y axes
#declare Fn2X = function(x,y)
{ (Fn1X(x+EPSILON,y)-Fn1X(x-EPSILON,y))/EPSILON }
#declare Fn2Y = function(x,y)
{ (Fn1Y(x,y+EPSILON)-Fn1Y(x,y-EPSILON))/EPSILON }
Note how the first derivative functions effectively "sample" the base
function at two points, and the second derivative functions do the same
for the first derivative functions.
(Also note that this formulation of the second derivative is
inefficient, as it results in sampling the base function four times:
Once at an offset of -2*EPSILON, once at an offset of +2*EPSILON, and
twice at an offset of 0; computing the second derivative directly from
samples of the base function could reduce this to three samples.)
The slope can then be computed from the first derivatives, and the
curvature from the second derivatives, both of which I leave as an
exercise to the reader (academic parlance for "I don't have the patience
to figure it out" ;))
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On 04/08/2016 02:24 PM, clipka wrote:
> Am 08.04.2016 um 09:49 schrieb Jaime Vives Piqueres:
>> El 08/04/16 a las 06:45, Cousin Ricky escribió:
>>> My instinct would be to avoid the analysis approach, and do sampling
>>> on the original function. That doesn't take a lot of sophisticated
>>> math. I can't even remember the chain rule without looking it up
>>> (and the last time I did so was, like, 2005), but I have used
>>> sampling to estimate normals on a form based on parametric functions.
>>> I did this for the smooth triangles of the elliptical toroids in
>>> RoundEdge. Normals, of course, can be easily converted to slopes.
>>>
>>
>> I'm still trying to grasp the concept of "sampling a function"... ho
w
>> I would do that? With another function? If someone can please post a
>> simple example...
>
> // Base function
> #declare Fn = function(x,y) { /* whatever */ }
>
> #declare EPSILON = 1e-6;
>
> // Approximate first derivatives along the x and y axes
> #declare Fn1X = function(x,y)
> { (Fn(x+EPSILON,y)-Fn(x-EPSILON,y))/EPSILON }
> #declare Fn1Y = function(x,y)
> { (Fn(x,y+EPSILON)-Fn(x,y-EPSILON))/EPSILON }
>
> // Approximate second derivatives along the x and y axes
> #declare Fn2X = function(x,y)
> { (Fn1X(x+EPSILON,y)-Fn1X(x-EPSILON,y))/EPSILON }
> #declare Fn2Y = function(x,y)
> { (Fn1Y(x,y+EPSILON)-Fn1Y(x,y-EPSILON))/EPSILON }
>
There's a missing (2*..) in all formulas. It should be:
#declare Fn1X = function(x,y)
{ (Fn(x+EPSILON,y)-Fn(x-EPSILON,y))/(2*EPSILON) }
and the same for the others. OTOH if all you want is to know whether it
is positive or negative then you can drop the whole "/EPSILON".
Jerome
--
mailto:jeb### [at] freefr
http://jeberger.free.fr
Jabber: jeb### [at] jabberfr
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Am 08.04.2016 um 19:21 schrieb Jérôme M. Berger:
> There's a missing (2*..) in all formulas. It should be:
>
> #declare Fn1X = function(x,y)
> { (Fn(x+EPSILON,y)-Fn(x-EPSILON,y))/(2*EPSILON) }
Indeed. My bad.
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Hi Jaime,
just following up: how far are you with this amazing scene? Still
interested in the scene code as I want to use your way to create a
realistic ocean surface in some maritime scenes.
Sven
On 02.04.2016 02:36, Jaime Vives Piqueres wrote:
> El 01/04/16 a las 22:45, Sven Littkowski escribió:
>> This is the most realistic ocean I have seen so far! Will you
>> publish the scene source code?
>
> Thanks... of course, sources will be published once I finish fiddling
> with it.
>
>> Just the sky is pink and some dust does not allow to see very far, so
>> it seems.
>
> Well, the sky is from CIE_Skylight.inc, and yes, I've never been very
> satisfied with the pinkish coloring at horizon. On the first image is
> less noticeable as I lowered the white point to 4000K.
>
> The dust/haze is on purpose, to hide the fact that the sea is a mesh
> with a finite resolution.
>
> --
> jaime
>
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El 23/02/17 a las 16:42, Sven Littkowski escribió:
> Hi Jaime,
>
> just following up: how far are you with this amazing scene? Still
> interested in the scene code as I want to use your way to create a
> realistic ocean surface in some maritime scenes.
I'm sorry but I've not worked on it since then... it's been on my
"pending to clean and publish" folder for months. Let's see if I can do
that this weekend...
--
Jaime
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That would be wonderful. I am looking forward, and I am sure, many
others do, too. :-)
On 23.02.2017 16:51, Jaime Vives Piqueres wrote:
> El 23/02/17 a las 16:42, Sven Littkowski escribió:
>> Hi Jaime,
>>
>> just following up: how far are you with this amazing scene? Still
>> interested in the scene code as I want to use your way to create a
>> realistic ocean surface in some maritime scenes.
>
> I'm sorry but I've not worked on it since then... it's been on my
> "pending to clean and publish" folder for months. Let's see if I can do
> that this weekend...
>
> --
> Jaime
>
>
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El 23/02/17 a las 22:51, Jaime Vives Piqueres escribió:
> El 23/02/17 a las 16:42, Sven Littkowski escribió:
>> Hi Jaime,
>>
>> just following up: how far are you with this amazing scene? Still
>> interested in the scene code as I want to use your way to create a
>> realistic ocean surface in some maritime scenes.
>
> I'm sorry but I've not worked on it since then... it's been on my
> "pending to clean and publish" folder for months. Let's see if I can
> do that this weekend...
>
Hmmm... not much luck this weekend: seems I made a mess of the code
with later tests, and I'm still trying to get something as good as the
images I posted here. :( ...will keep working on it this week if I can
find some free time.
--
jaime
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