Shading a Character made of Water

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  03 March 2005
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.
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Lazhar Rekik
 
  03 March 2005
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
Attached Images
File Type: jpg plate_paint.jpg (50.2 KB, 62 views)
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www.andrew-whitehurst.net

 
  03 March 2005
Originally Posted by Andrew W: 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


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.
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  03 March 2005
Originally Posted by Andrew W:
Hope that helps,

Andrew


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.
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Lazhar Rekik
 
  03 March 2005
Originally Posted by lazzhar: 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.


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?

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


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
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www.andrew-whitehurst.net

 
  03 March 2005
Originally Posted by Andrew W: 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?


Yes I'm using Maya and rendering with Mental Ray. I didnt meant that the plane didnt appear in reflections and refractions, no, if you look closely to the seperated rendering you can notice it. but I think that I need to use several white planes in different places to get the strong reflections over the surfaces, or likely paint manualy an HDR pictures with strong white spots to use as envirement.
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Lazhar Rekik
 
  03 March 2005
Originally Posted by lazzhar: I think that I need to use several white planes in different places to get the strong reflections over the surfaces, or likely paint manualy an HDR pictures with strong white spots to use as envirement.


or make the window polygon bigger than in reality to give a more pronounced effect perhaps?

A
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www.andrew-whitehurst.net

 
  03 March 2005
Yes, I think exagerating a little bit would give better results. But as I'm not willing to use this background in the final worl I really dont want to go far.
I've tested the same rendering way to render out this small animated(just moving and rotating) with another BG and envirement.
http://members.lycos.co.uk/lazzhar/cg_tests/wat02.mov (676 K with MJpeg codec)
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Lazhar Rekik
 
  03 March 2005
Hey lazzhar,

Could you post a still rather than the movie, my browser at work just doesn't like the movies you're posting...?

Thanks,

A
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www.andrew-whitehurst.net

 
  03 March 2005
Ah sorry Andrew, I thought the mjpeg codec works fine under linux. But it seems that the whole format is not welcome under this system.
Last time I was learning Shake under Linux I was very upset that it doesnt support Qtime.
Anyway I've used images sequence instead:
http://members.lycos.co.uk/lazzhar/cg_tests/wat_an/
Hope it works.
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Lazhar Rekik
 
  03 March 2005
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