Shading a Character made of Water


#1

Hi,
I’m tempted to render an animated chacacter made completly of water. First I thought it’s a simple task, but definitely it wasn’t so easy. Whatever I do, I’ve got somthing like a glass or another substance. I was looking for some references but I failed to find something close to what I want. I looked to some shots from the last “007” movie where there was some women flying, but they were looking like an ice or somthing because the water didnt look clean. I remember Abyss there was some nice water effects but cannot find it.
I’m aimed to shade a smooth and clean cartoonish character, while he still looks believable.
So any idea about how to make a character looks like a water while keeping his overal shape and has some expressions.
This is my starting point. the shading applied on a turning old model of mine.
http://members.lycos.co.uk/lazzhar/ad/wat1.mov (300 KB)


#2

it looks like it has too much specularity going on…


#3

Have you tried looking at Hollow Man? Or X men 2? And get a good HDR environment map for your reflections.

Simon


#4

LOL, Simon you edited your post and I wanted to answer the first one :wink:
Anyway,
I’m using a reflection map, not HDRI but I could switch to one later.
I remember Hollow man, but I gues he was not made of water, the man was invisivle and got wet. But I’m gonna watch it again. I’ll check X men 2 too. thanks


#5

Yeah well I just read percydaman’s answer and it made more sense. Adding bubbles would probably make it look like a glass man with water inside :wink:

How about a rougher spec map? (animated?) And maybe use just area light sources rather than specular (it’s a hack anyway - and not a very good one).

A sort of inside out version of what you want http://www.scififilmmusic.com/bootcovers/hollowman_inside.jpg ?

Simon


#6

Yes if i render somthing close to the picture you posted the link it would be ok. but as you mentioned I think i’ll use some animated bump or specular.
I’m not sure to understand what you said by using one area light. Is it for generating the glossiness or what?


#7

When you use phong specular it gives you a circular highlight which is meant to approximate the reflection of your lightsource. However if you have something really reflective then you can see the actual shape of your lightsource so it is better to use real reflections - either raytracing against incandescent cards, or painting them into your environment map.

Simon


#8

agreed…water, being such a smooth surface, would have little specularity… it would be best to just paint in your light sources into your reflection map. I knew the lensflare in photoshop would come in handy one of these days…


#9

The best thing to do will be to get a good hdri map. You’ll need something behind to refract as well, and make sure you’ve got your index of refraction set to 1.33/1.34, and that your shader’s doing a proper fresnel blend between the refractive and reflective components.


#10

So the refraction would have a reverse fresnel effect?

What about bluring reflections and refraction, does this help or not?


#11

Hi,
I’m just a newbie, but if I would like to make him look like made of water I would add some sort of surface motion like in abyss or those demons in kaena or maybe adding some dirt particles flowing inside him.


#12

Yeah, basically. Fresnel should give you coefficients for reflection and transmission: kr and kt, respectively. So your reflection shoud be scaled by kr and your refraction by kt. You can always just invert kr to get kt (i.e. 1-kr).

Assuming your water is clean, it should basically be a perfectly specular material, so reflections (including specular) and refractions are all you need. This also means that you definitely don’t want to blur anything: all components should be nice and sharp.


#13

I got it.
I’m not a shader writer and I dont want to be. But my thoughts went to render out 3 passes: reflections, refrations and a matte using a velvet look and use this last one to drive them in post. Correct?


#14

That’s probably going to give you the most control yeah. I’d definitely use a proper fresnel pass for your matte though. In my experiece for these sorts of things going physically correct nearly always works better. You can always pull the falloff around in 2d whatever you render out, but a fresnel with the right IOR will get you a good look straight away. It’s little things like that tell our brain “that’s water”, instead of “that’s plastic”.

btw. I couldn’t view your video with mplayer on linux. What codec did you use? And keep us updated with how it goes. Good luck!


#15

It’s sorenson. I think this codec is not working properly under linux. But sometimes it works fine the few times I run my linux.

Well the character is not finished yet, but I wanted to start the shading work first. I’ll finish the modeling and start testing and post results in this thread.


#16

The issue is that we’re not used to see waters walking through us. That’s why I think that we have some freedom in “cheating”
Anyway, I’ve tryed to use the first version of my character with a 5 min skining. I basicly used an image plane( found in the net i still dont shoot) to see well the refractions. I also put the same picture in a big sphere for reflections(I’ll switch to better solution late).
Well, when I started rendering the refraction it looks like the old problem I was having with them is present. You’ll get some black spots on the surfaces, but I think it’s not a problem because it generate their transparency in the alpha channel.

This is a sample:

So here is the clean BG

So the fresnel pass wich I call it velevet pass with shadows.

Then the plain Reflections:

And the Refractions

Now in post production we use the fresnel pass to key out the reflection

And invert the fresnel pass and use it to key the Refraction

Then the final composite:

I just put the layers with a slight tranparency and didnt know if I had to use any other blending mode like Add or Multiply…etc
All that and I dont have a Color pass. I wonder if I need one or not for such a substance like water. I’m thinking in an SSS one.

This is all, hope I’m going on the right path and the server wont go down and pictures stop showing LOL.


#17

Hi lazzhar,

I couldn’t get your previous movie to work so I’ve been waiting for some images before I posted. I think you pretty much have the elements you need but I think you could comp them a little better. For what it’s worth I’ve attached (I think, assuming it’s worked) something I put together in 5 minutes in Photoshop. Please forgive the nasty edges and bad paint work but I hope it shows the idea…

I’ve added a bit of contrast to the fresnel layer and made it so that high levels of reflectivity are still seen on the camera facing surfaces, but it is still more reflective at glancing angles. I’ve also badly painted in some reflection hot spots for the window. You could do this by putting an incandescent plane in your scene in the same place as the window in the plate and raytrace a reflection and refaction pass for that to add it into the mix. At the moment your image doesn’t have the “zing” I’d associate with such a reflective surface. You could also use a HDR environment map of the plate if you have one to achieve the same effect. You’re nearly there, you just need to tweak your elements and add some hotspots for the window (and any other bright light sources in the scene).

Hope that helps,

Andrew


#18

What he said.

The fresnel should never go completely black or white (but very nearly white right on the edge), and it should be clamped a lot more toward the edges than it is currently.

Water by itself is completely specular, so unless you’ve got stuff in it, you won’t need a diffuse pass of any kind, although you might want to tint it very (very!) slightly blue.

I think what would also help is if you introduced some ripples. This will be especially important if the character is to be animated: after all we never see water hold its shape unless it’s perfectly still.


#19

Hi Andrew, sure it helps.

In fact I did what you mentioned about adding a one polygon with incandescent white color. I even gived it a “super” color range but in vain. It just rendered like that. But as I’m using this picture just for texting the shading, I didnt care a lot.

For the Fresnel, I was able to use apply a level operator(in combustion btw) and tweak it until I get the colors I want.

for the ripples, what about adding them just in post? Or is it better to render them on all passes too?

And yes thanks for helps.
PS: The video is just a turning model I dont think it’s interesting anymore.


#20

That puzzles me. That should work even in the regular Maya renderer. You have made sure that the plane is visible to reflections and refractiosn? That option is set in the Render Stats settings of the attribute editor. Are you still using Maya?

I think you should do this in the 3D as the change in the surface normals with the ripples caused by the bump (or preferably displacement) will radically change the reflection and refractions and you won’t really be able to cheat that in the comp.

Andrew