I still think this wouldn't solve my problem, all it does is add noise on 
top of the controlling function, so you still get sharp edges.

You should render the close up with a lower camera position, so it has a 
more edge-on view of the sharp edge, at the moment the sharpness is mostly 
round the edge of the blobs so you can't really tell how sharp/smooth it is.

-- 
Tek
http://evilsuperbrain.com

"Kenneth" <kdw### [at] earthlinknet> wrote in message 
news:web.45632ef1a91bd327dc4a63960@news.povray.org...
> Tek's recent beautiful and complex ocean wave images got me to thinking
> about adding noise blobs to the tops of isosurface wave crests, to see if
> the look of foam and spray could be better simulated there, to some 
> degree.
> Certainly not a new concept. ;-) The essence of the idea involves the 
> noise
> being constrained, more or less, to only the tips of the waves, "fading 
> in"
> in intensity there. I vaguely remember seeing some POV-Ray images that may
> have used this trick, but can't remember where.
>
> An interesting question was raised, about whether the noise blobs--being
> smooth by nature--would assume a "sharper" look due to the underlying 
> sharp
> wave crests. I made some tests to see what might happen; the isosurface 
> code
> is posted below.
>
> My *quick and dirty* water waves are just triangles (from a pigment
> function) bent with a cosine wave to curl over, plus noise. Good enough to
> test the idea. The wave crests curl in the +z direction.  BTW, the 
> triangle
> waves aren't actually "bent"--they're SHEARED in the z direction. Every
> point on the isosurface stays at the same height it began at (a limitation
> of my own current understanding of function-bending.)
>
> Just to keep things as simple as possible, the noise "appears" at a set
> height, rather than being made to follow any vertical undulations (though
> it does follow the wave curls, in z, to impart a wind-blown look.)
>
> Image #1 is just a "proof of concept."
> #2 is a close-up, to see what the noise blobs look like--whether they're
> still blobby, or look like sharp, flattened spikes due to the triangle
> waves. Looks like a cross between the two. But even seen edge-on, they
> still look reasonably rounded. The noise intensity is fading in so quickly
> that it seems to overwhelm the sharp triangle edge. Part of the blobbiness
> appears to be out beyond the edge anyway.
> #3 is with some choppy distortion laid onto the isosurface. Since both the
> noise position and the gradient y texture don't move, the white "foamy"
> areas happen to correspond to the noise blobs. Interesting!
>
> Unfortuntely, every value in my noise_compressor function is critical, due
> to the exponent behavior. The values have to be finessed, to constrain and
> position the noise *just so.* I'm still not satisfied with the final look;
> needs more tweaking.
>
> The contained_by box's upper y dimension is also critical, to keep the 
> noise
> from quickly fading back in above the waves (a result of the way the
> noise_compressor function is currently built.) That might(?) be a problem
> for more complex water waves. But there are methods of using the 
> underlying
> water-wave function(s) to make the noise follow any changes in wave
> height...so the contained-by box size may not be a problem. But right now,
> there IS an abrupt (and probably apparent) cut-off of the noise right 
> above
> the wave tips. I'm still experimenting to find a way around that.
>
> What I see a need for--just from this basic experiment--is to scale the 
> SIZE
> of the noise blobs in the +y direction, larger to smaller. The result 
> would
> be a two-fold improvement, I believe: to make the noise larger and 
> smoother
> as it *approaches* the wave tips; but then tiny and more pronounced AT the
> tips. Given a set noise intensity in the noise_compressor function.  But I
> don't yet know how to variably scale a function's "size" across space. :-(
>
> Does the blobby effect add realism?  That's...a good question.  I kind of
> like it. With some good water waves and textures...?
>
> Here's the isosurface code, for image #1. If anyone is interested, I'd be
> glad to "deconstruct" the various functions, as to what they do (though 
> I'm
> still learning the finer points of functions myself.) I'm sure they could 
> be
> improved.
>
> Comments, critiques, suggestions--all welcome. This is definitely a 
> learning
> experience!
>
> Ken Walker
>
> -----------
> #include "functions.inc"
>
> #local triangle_waves =
> function{
> pigment{
> gradient z
> triangle_wave
> color_map{
> [0.0 rgb 0]
> [1.0 rgb 1]
> }
> scale .35
> }
> }
>
> #local wave_bender =
> function(y){.13*cos(11*y - 1.9) + .6};
>
> #local noise_compressor =
> function(y){775*pow(y + .390,30)};
>
> isosurface{
> function{
> y - .3
> + triangle_waves(x,y,z + wave_bender(y)).gray*.13
> - f_noise3d(150*x,100*y,100*(z + wave_bender(y)))*noise_compressor(y)
> }
> threshold 0
> max_gradient 6.3
> accuracy .00001
> contained_by{box{<0,0,-.6>,<1.2,.328,3>}}
> }
>
>
>
>

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