Lighting Challenge #5: Under The Boardwalk

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Old 06 June 2006   #46
MasterZap,

I work in Maya and MR and I am using a parti volume with
- A directional light for caustics only
- A spot light mapped with a MR physical light for volumetric effects.

The problem is that if I play with the caustics light, it either makes extremely bright, all-over caustics, or close to nothing. If I play with the volumetrics, either I set a very high extintion, in which case I see the light rays, but I don't see the caustics anymore, or I set low extintion, so I see the caustics, but I lose the volumetric effect.

I am trying to get an effect similar to this:
http://www.pbase.com/image/58647264
The idea would be to have the light rays shining through the peer boards and into the water. If only I could get it!!!
I am thinking of doing it in passes, but I don't have Maya 7 and I don't know if I can do it with some trick. On this regard, I have a few questions for you gurus:
1) You know how it is possible to have an object's primary visibility off, but still have it cast shadows, be visible in reflections, etc. Is there a way to make an object invisible, but still participate in caustics?
2) I am using a plane with bump map for the water surface. The problem is that if the bump value is low, I don't get too much refraction but the caustics are almost zero, while if the bump value is high, caustics look great, but the refractions are ridicolous. What the... ??? I have the refraction index of the water material down to 1.1 and still...
3) Can caustics be baked?

Thanks y'all!
__________________
Sy.

www.silviapalara.com
 
Old 06 June 2006   #47
Talking

Originally Posted by silvia: MasterZap,
The problem is that if I play with the caustics light, it either makes extremely bright, all-over caustics, or close to nothing. If I play with the volumetrics, either I set a very high extintion, in which case I see the light rays, but I don't see the caustics anymore, or I set low extintion, so I see the caustics, but I lose the volumetric effect.


Ah, physics at work. It's hard to get both in a physically correct manner (even in real world photography). What gamma are you rendering at? Any tonemappers involved?


Quote: 1) You know how it is possible to have an object's primary visibility off, but still have it cast shadows, be visible in reflections, etc. Is there a way to make an object invisible, but still participate in caustics?


Methinks that making it invisible to camera still makes it do all them other things. Worst case you can use a ray switching node like francescas ctrl_rays

Quote: 2) I am using a plane with bump map for the water surface. The problem is that if the bump value is low, I don't get too much refraction but the caustics are almost zero, while if the bump value is high, caustics look great, but the refractions are ridicolous. What the... ??? I have the refraction index of the water material down to 1.1 and still...


Hmm.

Quote: 3) Can caustics be baked?


I'm a mr person not a maya person, so I can't answer for maya's baking tools per se. But caustics are considered indirect illumination by mr. If you can bake that, then yes, you have baked the caustics.

/Z
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old mr blog: mentalraytips.com | Stuff: www.Master-Zap.com | Follow me on TWITTER
 
Old 06 June 2006   #48
@ mayadesigner - Thanks, and Welcome! Add whatever you want to the scene (new models, more copies of the models that are there, new paint effects, new particles, etc.) as long as you remember what people care about here is how you render it.

@ slatr - Bubbles could be a good idea. If I had a choice between reflections and transparency for the water surface, I know it should do both, but I'd start with some transparency instead.

@ oxygencube - Welcome!

@ silvia - If it's hard to get caustic effects in combination with other things, I'd say just render the caustics into a texture map, and project the texture map from the light. Caustics on the bottom of the lake are just a general pattern, not something that needs to be specifically registered with parts of the scene...

@ Popeye9 - Nice! It definately looks murky right out of the gate. I agree some beams of light through the water would look nice.

@ MasterZap - Nice! Very interesting render. I wonder if your sky could be brighter, like where you see it at the top of the frame, so it looked like it was brighter above water than underwater?

@ neuromancer1978 - You've definately got that underwater feeling. It would be great if there were a better sense of contact between objects and the ground, like more shadows or occlusion, and maybe a center of attention (even giving the fish a different color and letting some light hit one of them) to add some interest? I don't know if raytracing is always necessary for rendering the bottom of a water surface - maybe look at Finding Nemo for inspiration?

-jeremy
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Jeremy Birn
Author, Digital Lighting & Rendering, 3rd Edition
 
Old 06 June 2006   #49
Originally Posted by silvia: 1) You know how it is possible to have an object's primary visibility off, but still have it cast shadows, be visible in reflections, etc. Is there a way to make an object invisible, but still participate in caustics?

Yes, Mental Ray's Render Flags aren't under the shape nodes like the Maya Render Stats, they are up a level in the transform node, but if you turn off "Derive from Maya" they override them, and have separate switches for Caustic and Globillum. (At least in Maya 7 this works, don't know about which previous versions have which flags there.)

Separate copies with different render flags should solve your #2 problem as well.

Originally Posted by silvia: 3) Can caustics be baked?


Maya 7 can bake caustics and all lighting into texture maps, but that's only for surfaces that have good UV's, so you'd need UV's and maps on all the plants, everything, and to combine baked maps with regular lighting you'd need to put together that as an ambient component of all your shaders. You can also store and re-use photon maps, I haven't done as much with that.

For a generalized pattern like you show in that reference picture, I'd work on rendering it out as a separate image, then project that image from a spotlight. Or else use it as a transparency map that raytraced shadows from the sun shine through just below the water surface.

-jeremy
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Jeremy Birn
Author, Digital Lighting & Rendering, 3rd Edition
 
Old 06 June 2006   #50
Transparency in my scene

Thanks Jeremy, I may have to render 2 and comp them but I am going to try again to do both at once.

Did anyone notice I had shadows turned off I may have to render those in a separate pass/render too and comp them in.


Quote:
@ slatr - Bubbles could be a good idea. If I had a choice between reflections and transparency for the water surface, I know it should do both, but I'd start with some transparency instead.


 
Old 06 June 2006   #51
Here is my first wip entry. Alot of texture work to do, and it needs to be more murky etc.
Attached Images
File Type: jpg wip_2.jpg (66.5 KB, 2049 views)
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Last edited by Dan Wade : 06 June 2006 at 12:11 AM.
 
Old 06 June 2006   #52
Cute the idea of putting the bucket underwater to keep company to the tire!!!

Thanks guys for the suggestions for my problems, I'll try them tonight.
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Sy.

www.silviapalara.com
 
Old 06 June 2006   #53
wow ! gr8 stuff here.. well I was kinda reluctant to show what I have now.. but what the heck

things to know :
- I'm using XSI
- I didn't use GI/caustics or anything special.. I still need to learn how to work with them first.. so I went faking as much as I can.

things I know I need to do :
- work on a better bump map for the water surface.. now it's just a default fractal.
- there's lots of texturing to do.. you can see a checker on the fish.. hehe
- add some light beams ( should I ? )
- add depris and such .. some particles.
- solve the problem with fog, right now I'm using "volume fog" shader for the pass, and that's why even the air above the surface has fog and it screws up everything out of water , I tried to use "layered volume fog" but I'm still not able to get the fog to stop where I want to. I'll keep searching for a way to trap fog under the surface.. if you know how to do it I'll be thankful.

things I don't know I need to do :
you tell me.. tear apart and don't pull your punches.

and thanks again to you jeremy and everyone involved in preparing the challenges.
Attached Images
File Type: jpg undertheboardwalk_test01.JPG (50.3 KB, 1229 views)
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Old 06 June 2006   #54
Here's my first shot. I'm having trouble compositing volumetrics in a seperate pass, but I'm sure it's just my brain today... I love these challenges.



Kev

Last edited by kevb3d : 06 June 2006 at 04:55 AM.
 
Old 06 June 2006   #55
Originally Posted by Sherif.Nagib: wow ! gr8 stuff here.. well I was kinda reluctant to show what I have now.. but what the heck

things to know :
- I'm using XSI
- I didn't use GI/caustics or anything special.. I still need to learn how to work with them first.. so I went faking as much as I can.

things I know I need to do :
- work on a better bump map for the water surface.. now it's just a default fractal.
- there's lots of texturing to do.. you can see a checker on the fish.. hehe
- add some light beams ( should I ? )
- add depris and such .. some particles.
- solve the problem with fog, right now I'm using "volume fog" shader for the pass, and that's why even the air above the surface has fog and it screws up everything out of water , I tried to use "layered volume fog" but I'm still not able to get the fog to stop where I want to. I'll keep searching for a way to trap fog under the surface.. if you know how to do it I'll be thankful.

things I don't know I need to do :
you tell me.. tear apart and don't pull your punches.

and thanks again to you jeremy and everyone involved in preparing the challenges.


Sherif.Nagib,

The things you listed are a good direction to go in. You've pretty much nailed the bases there. I used XSI for this one too and I found that I should probably show more above the surface, but I think that depends on the time of day, angle of the sun, incidence angle, etc.

I think that you have a good first shot, but it's really too early to tell anything yet. Keep going with it and taking people's advice as you go. These people here know their stuff and are some of the most helpful people on this board. Keep going and kick some ass.

Kev
 
Old 06 June 2006   #56
Hello,

I don`t know if I could finish this challange but this is what I have so far.
Textures, Volumetrics + Caustics are missing. Render is done in Lightwave (Fprime)
with one light for the sun and montecarlo radiosity with 2 bounces.

Marcus
Attached Images
File Type: jpg uw.jpg (73.0 KB, 728 views)
 
Old 06 June 2006   #57
Here again with an update. After MANY attempts at using custom light shaders to get caustic like patterns on the surfaces while using shadow maps.... I decided to say forget it and just went on using the standard Liquid light shadows (sigh).
Also doing any kind of occlusion with Liquid is like pulling teeth, so no go there.
However I did do a lot of shader work for the surfaces, some of the RSL shaders are almost 100 lines of code. There are however a couple of shaders by Rudy Cortes (the ground) and Larry Gritz (the rusty bucket), but for the most part all the shaders are my own (I feel so proud! LOL).
All in all I feel ok with this, but of course I will work on it some more.

 
Old 06 June 2006   #58
Originally Posted by Dan Wade: Here is my first wip entry. Alot of texture work to do, and it needs to be more murky etc.


This is what i'm looking for..
Great job Dan and the focus is amazing!

Cheers
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Old 06 June 2006   #59
Ultra quick mental ray/3dsmax setup here, no textures, GI/FG. volumetrics or caustics (yet). Only a skymap, one light source, a water texture, and the submerge(lume) shader for color...and a lot of Photoshop.

900 pixel image so I'll post a link instead of the image:
http://jeffpatton.net/Gallery2/Water-artsy.jpg

If I get time I will:
Add Caustics
Add particles & bubbles
Maybe comp and AOCC pass for the lighting
Add a volumetric light effect
Add textures
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Jeff Patton
My Website
 
Old 06 June 2006   #60
Thumbs up

JEFF! That's friggin' gorgous. Physics be damned. It's a painting!

I'm impressed.

/Z
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Mr Zap Andersson - Random Rendering Guy at Autodesk Inc.
old mr blog: mentalraytips.com | Stuff: www.Master-Zap.com | Follow me on TWITTER
 
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