sediment in water

[TheBadger]

Hi

been thinking on this on and off since the iceland contest.
http://cdn.rsvlts.com/wp-content/uploads/2013/02/lg_25961501_D4N5850obr.jpg

I have tried a few things, nothing clever. Just a couple of water shaders over one another... no hope there I think.
But I thought that maybe I could use clouds somehow.

Any thoughts on this effect? Anyone ever try it? A direction that would work? Usually I can see that something is possible or not, regardless if I can do it my self, but on this OP I am not sure either way.

Well so much for me just trying to have fun.

[fleetwood]

Having trouble making spatial sense of the image in your post, so not sure what effect you want. Is it the ropey look ?

For ordinary sediment I think I would as first choice use the volume 1 density features of the water shader , since it has function inputs for both the amount/shape and the colors.

I have put clouds under water before, but it if I remember right it takes a long time to render and the result IMO is not better than using Volume 1 density.

I attempted to simulate jade with the water shader and its volume 1 features. Again it took a horrendous long time to render.

[TheBadger]

@ Feetwood
Both your images show what I am after to a degree. Yes I am asking about the different water color created by the sediment. The shape of the river was very easy (though it took a whole day) I got VERY good results with that bit. The rest of this is much much harder to figure.

I thought at first I could use different depths for the water shader. So a lower level for one color, and a higher depth for the main color. But that does not do it really. In both cases your images show much more promise than what I tried at first.

@Allen
It does not have to be perfect. Even fleetwood's images are encouraging for me. The effect I am after is to be just a part of an image, not the focus, so I feel like I have a good bit of wiggle room where total realism is concerned. The viewer would not see as much as in the OP, so not have enough info to see that it is not real. I think.

@fleetwood
Can you post some clips from those files with some notation? They both show a bit of what I am after. Maybe they can be used together with some work, to get me very close. Close may well be enough in my case. At the very least I would benefit from seeing how you built it up.

...
Another idea about clouds for this
http://planetside.co.uk/docs/tg2/cloud_function_tutorial.pdf
In Martin's tut you can see how the clouds trace the terrain nearly exactly. I was thinking I could make a mask of a path within my river, and have the clouds only show up there. So the mask would be the shape of the sediment, and the cloud the sediment.. Just like fleedwood, but with the clouds tracing the terrain contours (within the mask) as in Martins tut.
I feel like this could give me the volume and depth I need to make the effect look real. The part I am not sure of is direction and a feeling of motion for that direction.... Perhaps I could animate only the clouds with motion blur on, and take a frame from that?

Thoughts?

[Kadri]

There are many ways to approach this. It depends on how you will use this. Will you be close and will it be animated for example?

If you look at the image you posted with a little try you could interpret that water even as ground with small moving dunes.

I would try a standard planet or plane object as water with masks for the sediment.
From this far away you wouldn't see the difference of depth and it would be faster to render too.
I haven't tied this and not sure if it would work for your scene.

[Oshyan]

The Water Shader Volume Density function is basically for this type of effect. It will vary naturally with depth of the water, which is really what is very likely happening in your reference picture and *not* a variation in the *amount of sediment* carried by water in that part of the braided stream. So basically the trick is creating the base river/stream bed shape, with appropriate altitude or water level to then have the volume density effect function correctly. It looks like some upcoming functions in World Machine might be helpful for creating the base terrain.

- Oshyan

[TheBadger]

I would guess that the water is deeper where there is more sediment in the water. And that where it is clear over black sand that is shallow. The water looks faster where there is sediment too.
Would be fun to wade there.

Allen
I like what you got already too. Looking forward to hearing what you figure out.

Kadri
Pretty close to the water

Thanks for all the ideas everyone.

[fleetwood]

An example using Volume 1 Density on a 20 meter lake.

What I did with the jade model is specific to an imported model of that exact size. In other words Volume 1 Density is very fiddly for each situation. The clouds in water is nothing fancy, just make little fog size clouds and lower their altitude till they are under the water surface, but again I can't recommend it.

I'm not sure you even need the water shader involved with what you want to do. Maybe stretched fractals and warps and a reflective shader might do it and no need for the water.

[bobbystahr]

Michael, here's a test I did some time back, 'tween all of these you should wind up with  decent sediment.

[TheBadger]

Thanks again all!
To tell you the truth I am a little surprised that there are so many ideas on this. I had thought my options would be pretty limited. So I am glad there is so much more wiggle room then I guessed there would be.

Though one concern is that most of what it looks like I can do will be to add something on-top of the water rather then in the water (visually). What I mean is that these would all be perfect solutions if I wanted to create an oil slick, for example. You know what I mean? it may also have as much to do with lighting as anything else though, as with clouds for example.

Well, still, I think these are all great, and will get me where I want to go on this!

@Allen
is that new image in sharing part of this, or something completely different?: http://www.planetside.co.uk/forums/index.php/topic,20096.0.html

[fleetwood]

Don't get the wrong idea from that example.
The volume 1 density is in the water. It only appears to lay on the water in the example because I  set density very high and the decay distance very short to make the pattern very strong.
Just play with those settings and you'll get many different results.

Here's the result with greater decay distance (5 meters) and density much lower (0.1) and a few waves added.

[Dune]

This might even be faked for faster rendering by using an altitude based mask for a simple silty PF+ small coverage surface layer on top of the water, or under a reflective shader.

[bobbystahr]

My solution used the volume of the water....not the syrface. Admittedly a bit primitive but it was an 'early days' test.

[j meyer]

Tg's water doesn't have a volume,so no volumetric effects possible methinks.
Or am I wrong?

[bobbystahr]

Tg's water doesn't have a volume,so no volumetric effects possible methinks.
Or am I wrong?

well it is a cool fake as you don't see it if the camera is below the surface but the labels in the Water shader do say Volume Density and Volume Colour...just what i see...

[TheBadger]

Tg's water doesn't have a volume,so no volumetric effects possible methinks.
Or am I wrong?

Yeah thats what I thought. but its all trickery no mater what right? One other thing I hope to try pretty far down the line, is to import the terrain into maya (for the most relevant part) and try to do the same thing with Maya's water system. And then either import the water to TG as a sequence, or composite. But I am really only trying to make some good stills, so the maya stuff would be over kill, though could give a real fun result. always best to just get it right in TG first though.

@Fleetwood
THis last image does look like the water has materials in it, from this view. So that is nice!