Sorry been working on updates to this but my PP2014 keeps crashing.

Quote - This image is a Poser render of my surface (and short-dive-submersible) grab-dredger. The sea surface is the ground plane re-colored and 50% transparent (edge transparency = 0%); the deep sea beyond visibility limit is the background with color red=0, green=128, blue=255. How could I make the effect of underwater visibility decreasing with depth, while keeping the air above water level clear?

(The big hole each side in its bows is the inlet and exit of a bow thruster)

There are several ways to do this, none of which are obvious or great. Given that Poser lighting has real volumetric scattering ability, we have various cheats.

If you have most of the light coming from a single infinite for the sun, you can set it to provide less light as the depth increases below a certain level in world coordinates.

It is not obvious how you'd do this, but it's fairly easy once you know how.

I will show.

Set up your infinite (sun) like this.

The key parameters are identified with boxes and arrows:

Transmission Attenuation Color - This is where you get to say what happens to white light as it descends through the water. Water attenuates red faster then green or blue so the red component should be lowest. Depending on the impurities also absorbing and scattering certain colors, the green can be more or less than the blue. You decide. In this case, I put RGB 160, 190, 200. I use gamma correction so those turn into RGB coefficients according to the rules of gamma correction. If you don't use GC, you may need to adjust this color.

Transmission Distance - This is the distance at which white light turns to the color you gave above. I set the shader up for inches, so this is saying white light becomes the Attenuation Color at 1200 inches. (100 feet) If you decrease the number, light will diminish more quickly. If you increase it, it will stay stronger deeper.

Water Level - This is the level of your virtual water surface, in inches. I have it here set to 2400 inches (240 feet). 

So - in this setup, the "ground" is 240 feet underwater and that is where my bottom is.

I have a curved backdrop with a "ground" or "bottom" at 0 inches. The ship rests at ground level.

At 2400 inches above it, I have a board that intersects with the curved backdrop wall. This is so you can see where 2400 inches is.

As you can see, the sun light decreases and changes color below 2400 inches. Above 2400 inches it is at its normal strength and is white.

Note that I'm using refraction. You were using transparency. Don't use transparency - it's completely fake looking.

The water surface bends the light. What is at the bottom should look flattened.

I used the same techniques to make this image recently.

Poser doesn't have any of that. I will show you how to add all of it.

Notice, also, that Poser doesn't know how to do the reflections from under the water surface correctly. This is a sore point with me. But no matter. I will show how to get them.

If you don't want to follow the math, you can skip, as I will be supplying the shaders. But there is a lot of math and knowing it will help you deal with realism in other situations.

For those who want to know the math of the Sun shader...

The P node gives absolute world coordinate position of whatever is being lit. It does so in units that are 1/10th of a Poser inch, or 1/1032 Poser Native Units.

I multiply the Y coordinate by .3 because I want inches (.1) and because the XYZ values get averaged as the output goes into a number. In other words, the output will be .3 * 10 * (Y in inches) / 3 which is Y in inches. Voila. We'll call this Y. In matmatic:

Y = P(0, .3, 0).asNumber()

Letting W stand for the water level in inches,

W = 2400

we need to know the depth (d) of the point being shaded below the water surface, so

d = W - Y

We don't want negative depth, so everything less than zero should be treated as 0. (Negative depth means above the water, and should be left alone).

d = Max(d, 0)

We're going to want to scale that depth according to some adjustable attenuation distance, D

D = 1200

d = d / D

The attenuation of light happens according to the exponential function. The attenuated light color RGB(160, 190, 200) goes into an exponentiation with the depth as the exponent and the color as the base.

C = IColor(160, 190, 200) ** d

That's the math for the sun shader.

Why does the negative depth (i.e. stuff above the water) not get changed?

Because for things above the water, we saw to it that d is 0. Any color to the power 0 is white.

Here's the entirety

C = IColor(160, 190, 200) ** (Max(2400 - P(0, .3, 0).asNumber(), 0) / 1200)

I always work in Poser units (1 = about 100 inches.)

Transmission distance = 15 (= 1500 inches = 125 feet, here.

 

To Bagginsbill :: hanks for the underwater light texture setting info; where could I get the realistic wave shapes from in your images above?

Do those wave shapes cause appropriate light refraction in light passing through the water surface?

As I use y=0 as water level, is it possible to use maths nodes in the Atmosphere texture to make one atmosphere setting above water level (= in air) and another atmosphere setting (including underwater visibility limit) below water level (= underwater)?

Light penetrates by diffusion underwater much further than the underwater visibility limit.

Quote - As I use y=0 as water level, is it possible to use maths nodes in the Atmosphere texture to make one atmosphere setting above water level (= in air) and another atmosphere setting below water level (= underwater)?

Yes. No matter what the water level, atmosphere settings can use the y coordinate to change behavior.

The one thing that can't is IBL (image based light). In an IBL, the P node doesn't do what we expect it to at all. Pity.

Quote - Here is the maths (light4, and the ground plane). (Lights 1 2 3 are off.)

I always work in Poser units (1 = about 100 inches.)

It may be that you work in PNU, but I set the shader to work in inches, because the P node is always 1/10th of an inch and ignores your Poser Display Unit.

So you actually set the transmission distance to 10 inches.

That's ok - sometimes water is that densely filled with particles. But if you meant 1000 inches you should type 1000 there.

When simulating very dense particle concentration, you would use brown or green, not blue, since the attenuation of water is not the main factor - it's the particulate matter suspended in the water.

If you really want to work in PNU, so that you can express the water level and the transmission distance in PNU, then you should change the Subtract node's Value_2 from 1.000 to 1/103.2 which is 0.00968992248.

Anthony you're still using transparency in your water plane, and adding a very blue diffuse reflection. Neither of those things should be happening.

The light color now shifts to blue and you don't need to fake it in the water plane.

Use refraction and reflection, modulated by a Fresnel_Blend node.

Thanks for your help. I have now tried Fresnel on the the surface node’s refraction_color channel. I always get all sky reflection :: I see that in Poser the water is absolutely flat, but in a real harbor there would be wind-raised small waves all over the dock water, making different refraction effects.

One step at a time. Waves are difficult. First show me your water shader with the Fresnel setup. If it's not right I'll notice.

The sea surface (= the ground plane recolored) is transparency=1, edge transparency=0, Diffuse Value = 0. (If I set both transparencies = 0, I always get the sea surface opaque.)

I have linked the refraction color to a Fresnel Blend mode, outer color = 0 10 200 (red first), inner color = 127 127 127

Here is a basic (no waves) water setup using Fresnel_Blend. The Fresnel_Blend node determines the amount of reflection versus refraction according to the Fresnel reflection coefficient equation. (i.e. real life)

Turn off shadows for the water prop and put this shader in.

Once you get to this, then you can experiment with waves in the bump channel.

However, that will be many days of discussion, so start with simple water and get used to that. I bet you will still have questions or do things wrong.

For example, I repeat: TURN OFF SHADOWS FOR THE WATER PROP.

Also: You need to enable raytracing and have at least 1 bounce.

Also: You will need a full 3D environment behind the water (at least an environment sphere) for it to reflect things like the sky.

Attached Link: http://larashots.com/appleyard/temp/renderosity/info.htm.

Looking good so far. 

Attached Link: http://larashots.com/appleyard/temp/renderosity/info.htm.

The ground plane (= sea surface) uses Ground Default Texture as a displacement map, with 'Displacement' = 0.1

The dock wall's brick pattern reflects distorted on the dock water, as would be with reflecting from waves. I suppose that the circular white scrawling on the sea is a maths side-effect aberration. But the sea level on the dock wall and the side of the dredger is flat level without wave humps.

I have been working all day on refining my procedural waves, so that I can give good advice about it. I've never felt I had it really right before for high-wind situations.

Here is a test render I just did.

I'm trying to get results consistent with a 45-knot wind. The waves are over 10 feet here.

Attached Link: http://larashots.com/appleyard/temp/renderosity/suw_01i_lightmat.jpg

Please where is information about the procedural waves that you mention?

You might start with ripples.

Ripples are nearly sinusoidal and we can get such shapes from a single node such as the Clouds node. Also, we don't really need displacement for it since the amount of displacement is very small. But I'll show it in displacement. You can use bump instead.

My display unit is inches!!! The displacement value here is .75 inches. If you do not set your Poser to inches, you'll have to type in something else. For PNU it would be .75 / 103.2, which is .00726744.

To get bigger waves we have to add many nodes together. Poser doesn't have a built-in node that does the proper math for ocean waves. I'm still trying to figure out what that math should be for all wind speeds from 1 to 100 MPH. It's complicated.

So start small and deal with ripples first.

You might also try to skip the attenuation of light and instead just darken and colorize the refraction as I've done here. I'm not using attenuated lights in this render.

Please, in a setup of texture nodes, how can I combine an Image_Map node and a P nose and whatever else to find the value of that image texture map color at point P as mapped onto a particular Poser material?

That is very difficult and requires careful coordination of the prop holding the "particular Poser material".

Could you explain more what you need to accomplish, instead of asking how you would do this particular subproblem? It may be entirely avoidable.

For example, my procedural water displacements are nodes connected to world coordinates and can be reproduced in multiple shaders, requiring no knowledge of the water's position, size, orientation, etc.

If you use an image map, then the UV mapping gets involved and it's desperately difficult to sort that out.

Attached Link: https://en.wikipedia.org/wiki/Wind_wave

It seems that Poser 11 or etseq needs a specific procedural water wave generator instead of having to use the cloud generator.

Right I already said that you have to start with ripples and bigger waves need more nodes.

I think your use of such a short attenuation distance, while fun, is not realistic. That looks like ink, not water. There is a reason I had such a large number in the parameter.

As I said, I think you should succeed at a rippled surface before you move on to the more complicated things. While I see you're using my techniques, you're using your own numbers and colors and it isn't coming out right.

If I add 24 more nodes to your setup and you mess with the numbers, you're only going to get insane results.

Those waves are looking pretty good, BB!

     It would take more node spaghetti, but I'm thinking of how to transition to add foam at points of high eccentricity (sharp peaks of waves).  I wonder if there is a way to sense proximity to the exterior of an object (hull of a ship), and display foam near such interface?

Quote - Those waves are looking pretty good, BB!

     It would take more node spaghetti, but I'm thinking of how to transition to add foam at points of high eccentricity (sharp peaks of waves).  I wonder if there is a way to sense proximity to the exterior of an object (hull of a ship), and display foam near such interface?

Thanks. I did a quick-and-dirty attempt to make the peaks foamy but I failed. I also tried AO to sense the ships nearby and failed at that, too.

For the moment I'm just making the foam randomly, but I'm working on it.

I keep running into weird Poser-isms. Look in the lower right corner. WTF?

(click for big version)

HAAA HAAA HAAA HA AHAHAAA

Unlike most of my posts, this is not one you're allowed to copy/share/redistribute/sell.

There - that will prevent you from feeling like you should try.

Grey boxes connected by colored wires, and in the end not exactly doing what's expected. Looks like my first analog computer build, decades ago :-)

In the meantime, waves are improving. Neat job, BB.

man, look at all the nodes!  it appears viivo may be response to nsa et al., unless they already broke public-key system.

Hah - I didn't notice the Viivo floaty thing got in there. Viivo is my main job - I designed it and built a lot of it. And, no, as far as we know, the NSA can't break it.

Thanks. Bagginsbill's technique looks good for small waves. I am sorry if I was too critical. Thankyou for all your good advice.

     Come to think of it, a ship's hull would probably need a wake mesh fitted to it.  That would give a "pipeline" bow wave and the rebounding bulge upward behind the stern.  The wake mesh could be given foaminess.

http://www.turbosquid.com/3d-models/free-obj-mode-ocean-sea-wave/629015

It offers huge waves that would normally overwhelm Poser's displacement system, no matter what the shape.

Here I combine it with my wave shader for the smaller waves.

The white box is 50 high and wide, 250 feet long.

The submarine is a similar size but harder to see.

So I'm going away for the weekend. If you want to play, I have placed a zip full of goodies for you to try:

https://sites.google.com/site/bagginsbill/free-stuff/ocean-stuff

This is bbocean-04.

There are more - speeds supplied are 2, 4, 9, 16, 25, 36, and 49 knots.

Due to a bug in my script, the foam color got set to black - the higher wind speed shaders will appear to have black spots.

To fix it, Find the Diffuse node - a Blender connects to it with a light blue in Input_1. Input_2 is black - that is the foam color - change it to white.