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Poser F.A.Q (Updated: 2018 Oct 17 3:56 pm)


 Subject: Underwater submarine

Helgard opened this issue on Jun 26, 2010 · 183 posts

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  Helgard    ( ) ( posted at 6:50PM Sat, 26 June 2010 


I want to render a submarine underwater. I want the water to be murky green as in the attached picture. I can get a pretty good effect using the atmosphere settings, but I was wondering if it was possible to do it just with coloured lights. Basically I need something that can render fast in an animation, and the atmosphere set-up I have is going to take literally weeks to render all the shots I need.


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  Helgard    ( ) ( posted at 6:51PM Sat, 26 June 2010 · edited on 6:51PM Sat, 26 June 2010 · @3663886


And just to be clear, i don't want a surface with caustics and godrays coming down, thisis slightly deeper and darker. And I am not looking for something like in this picture.


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  Helgard    ( ) ( posted at 6:52PM Sat, 26 June 2010  · @3663887


Maybe this will be more of the idea of what I am trying to achieve.


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  Helgard    ( ) ( posted at 7:09PM Sat, 26 June 2010  · @3663888


Possibly a better shot of what I am after. Just a little bit more green.


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  kawecki    ( ) ( posted at 10:42PM Sat, 26 June 2010  · @3663950

You can try with a background plane, one or more planes with transparecy and textures and a little depth fog.
The transparency planes can give you caustics effects and a curved background with some lights the background illumination.
Use few transparent planes, transparency renders much slower.

Stupidity also evolves!

  raven    ( ) ( posted at 7:47AM Sun, 27 June 2010  · @3664053


Have you tried just using depth cue on the atmosphere node?



  raven    ( ) ( posted at 7:48AM Sun, 27 June 2010  · @3664054


Those are the settings I used for this picture (which uses the free sub (scaled to 22% ) available at the DAZ archive here http://free.daz3d.com/free_weekly/detail.php?free_id=173 )



  raven    ( ) ( posted at 8:01AM Sun, 27 June 2010  · @3664057


And here's a quick anim of the sub emerging from the depth cue effect. 



  Helgard    ( ) ( posted at 8:05AM Sun, 27 June 2010  · @3664058

Perfect. Thanks, setting it up now.


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  bagginsbill    ( ) ( posted at 11:53AM Sun, 27 June 2010 · edited on 11:55AM Sun, 27 June 2010 · @3664123

One thing to note - the depth-cue effect in Poser is linear falloff, all the way to 0, which is not realistic. It makes the sub anim above look like the sub is materializing by passing through an opaque portal, instead of merely approaching the camera. True depth-based light transmission (such as fog or murky water) is actual an inverse linear effect, which never goes to zero at any distance, but approaches zero forever.

Some people don't notice things that are at least directionally correct, even if they are wrong in a numerical sense. This is the case with distance falloff. Some people notice, others don't. I notice very badly and it looks to me as bad as rendering without shadows.

If you find this a problem, I can show how to fix it.


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  Helgard    ( ) ( posted at 11:59AM Sun, 27 June 2010  · @3664129

I just needed something that will render very fast, and look sort-of acceptable.

This is not for any high end purposes, or for a gallery, but just to demonstrate an effect to people working on an idea.
 
If I wanted to do a high end render or animation I would just use Vue, much easier to get this effect in Vue.

I know the above is not the ideal solution, but it renders fast which is my main criteria for this.

Thanks for the offer though.


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  bagginsbill    ( ) ( posted at 12:07PM Sun, 27 June 2010  · @3664131

I'm talking about the above solution - using depth-cue - not something else.  It simply involves connecting a couple nodes to the Atmosphere node. If you're happy with it as is, that's fine. My point was that with no cost to speed, you can get a quality improvement.


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  seachnasaigh    ( ) ( posted at 12:09PM Sun, 27 June 2010  · @3664133

I'd be interested in the asymptotic depth cue, BB.  I've got an elvish submarine in the works which could use it.

Poser 11 Pro SR 8.34338, in Poser native units.  

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  Helgard    ( ) ( posted at 12:27PM Sun, 27 June 2010  · @3664143

Bagginsbill, yes, then I am definitely interested.

Just a question, what do you have your units set to in Poser? I was trying one of your shaders from one of the other threads, and it wasn't looking right, but I assume it was because I have my units set to something different to yours.

Thanks in advance...


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  bantha    ( ) ( posted at 12:45PM Sun, 27 June 2010  · @3664159

 BagginsBill uses Inches. 


A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
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  Helgard    ( ) ( posted at 12:50PM Sun, 27 June 2010  · @3664162

Thanks. I was using the metric system.

(Inches: a measuring system so old that even the people who invented it don't use it anymore, lol)


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  SamTherapy    ( ) ( posted at 6:45PM Sun, 27 June 2010  · @3664345

Oh yes we do.  Well, some of us do.  I use both.  :) 

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  raven    ( ) ( posted at 6:23AM Mon, 28 June 2010  · @3664524

I never said it was perfect! :)  I did delete about eight frames at the start of the anim in Animation Shop to make the file size smaller, so it didn't quite just materialize :)

At the end of the day it was just a quick idea that required no node wizardry for people (example me) who don't know the ins and outs of the nodes.  I'd love to have the better version of depth cue too.

And I know, it didn't have GC enabled either! :)



  bagginsbill    ( ) ( posted at 7:10PM Mon, 28 June 2010  · @3664808


Hi folks. I have done some experimenting with the Depth Cue to get it perfect.

I need to go make something to eat, but meanwhile I thought I'd show you the effect.

Later, I'll post the shader, and an explanation of how it works. You don't need to know how it works to use it. But for those interested, I will show how I constructed it.

First a little explanation of my test scene.

I have two of those subs from Daz. There are also a bunch of poles. The small poles (which are red in the renders) are every 20 feet from the XY plane. Every 100 feet is a large (white) pole.

The camera is in the XY plane.

The closer sub's conning tower is even with the pole that is 100 feet from the camera.

The farther sub's conning tower is 250 feet from the camera, halfway between the 200 foot and the 300 foot pole.

The attached image shows the layout looking from the "Top" camera.


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  bagginsbill    ( ) ( posted at 7:13PM Mon, 28 June 2010 · edited on 7:14PM Mon, 28 June 2010 · @3664809


I set up a "traditional" depth cue, with the start distance at 0 and the end distance at 160 feet.

This means that the "transmission" of light from the objects is 50% at 80 feet, and 0% at 160 feet.

If you count the poles, the last one you can see is the one at 140 feet. The pole at 160 feet (and everything behind it) is invisible. The sub seems to materialize out of nowhere at 160 feet.

This is not how it should look.

Click for full size.


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  bagginsbill    ( ) ( posted at 7:17PM Mon, 28 June 2010  · @3664811


Now I do the math. As before, the transmission is 50% at 80 feet. But, with the correct asymptotic falloff, the transmission is 25% at 160 feet, not 0. At 250 feet (where the second sub conning tower is) the transmission is about 11.5%. At the tail of the second sub, about 360 feet away, the transmission is about 4.4%. The transmission never goes to 0.


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  DarkEdge    ( ) ( posted at 7:48PM Mon, 28 June 2010  · @3664817

Another absolute work of beauty BB, that last pic looks very real.
If I may indulge you for 2 things:
1- What the heck does a asymptotic look like in Poser terms, nodes, etc?
2- How did you get such realistic caustics? Again in Poser terms, nodes, etc.

Can you post pics if you are using nodes for this please? 😄

Comitted to excellence through art.


  bagginsbill    ( ) ( posted at 8:05PM Mon, 28 June 2010  · @3664825

Will do - but first I have to get in my car, go to my apartment, and eat something. I'm starving!


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  Miss Nancy    ( ) ( posted at 9:37PM Mon, 28 June 2010 · edited on 9:45PM Mon, 28 June 2010 · @3664849

Attached Link: http://www.renderosity.com/mod/forumpro/showthread.php?message_id=2741994&ebot_calc_page#message_2741994

bill posted sub caustics method in 2006.  as usual, find by searching poser forum,
username bagginsbill.  inverse square falloff plugged into volume colour/density channel
is more recent addition to his earlier technique**. ** whilst carrara can calculate wave-generated
caustics quickly, mark bremmer (carrara expert) recommended method similar to bill's.
**
**



  bagginsbill    ( ) ( posted at 12:29AM Thu, 01 July 2010  · @3665923


Hi all - just a quick note to let you know I haven't forgotten about this. It got me thinking about some other things, such as how the light should decrease with increasing depth, as well as with distance, and how the scattering from particles should appear.

Here's a little demo of where I'm at. The water surface is 200 feet above the bottom (ground). You can see sky through it. Notice the area of total internal reflection. But! There's an anomaly due to the fact that reflections of the distant areas, which should be dark, come from the surface which is much closer. The Atmosphere effect does not respect the total distance that info has traveled - it only deals with the direct distance between the surface and the camera. I'll have to fix that with some more math - seriously complicated math.


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  richardson    ( ) ( posted at 6:31AM Thu, 01 July 2010  · @3665979

book


  Helgard    ( ) ( posted at 6:33AM Thu, 01 July 2010  · @3665980

We are not impatient!! We can wait for perfection, lol, and we demand nothing less. :-)


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  bagginsbill    ( ) ( posted at 10:17PM Wed, 07 July 2010 · edited on 10:18PM Wed, 07 July 2010 · @3669344


Well, after another week's work on it, I'm happy to say I think I've got this pretty well nailed.

It took a rather large amount of work with algebra, trigonometry, and calculus. I don't often find much need for calculus in shader work. But to get the correct behavior of the attenuation and scattering of light caused by tiny particles, I needed it. I had to do line integrals in a 3D field.

78 nodes later, this is the result. Click for full size.

Now the question is - does anybody want to see how I did it, or do you just want the shader?

Note: I really should sell this shader as it is truly a masterpiece, even for me, but what the heck. I'll give it away. There's probably not a very big market for this effect.


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  bagginsbill    ( ) ( posted at 10:35PM Wed, 07 July 2010  · @3669345


In the previous render, the camera was at a depth of 75 feet below the water surface. (The ground is 100 feet down.)

In this render, the camera is only 20 feet below. Observe how the scattered light is arranged differently, because of the camera position.


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  nruddock    ( ) ( posted at 2:59AM Thu, 08 July 2010  · @3669399

Quote - Now the question is - does anybody want to see how I did it, or do you just want the shader?

I for one want to see the workings behind the final shader.
Maybe do a PDF so that it's easier to reproduce the calculus equations.


  Helgard    ( ) ( posted at 5:05AM Thu, 08 July 2010  · @3669425

I am not too old to learn. I would like to see how it was done, although I am not guaranteeing that I will understand it the first time.


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