View Full Version : Underwater Dock lighting

12 December 2010, 06:01 AM

I'm trying to figure out the best way to light this scene. I'm going for minimal lighting with rich blacks in shadows. The port holes should be the source for the light from the ocean, there is a light pool and one at the top of the door.
The last image is what i composited in Photoshop to give an idea of what I'm going for. I'm also interested in getting some caustics along the wall.

Do I need to use portals?
To achieve a sense of volume, do I need to use particles?
I feel as if i'm totally overlooking the simple and making this way more complicated.

I'm great full for any help I can get.

12 December 2010, 05:53 PM
For the volumetric effect you can use the mib_party_volume shader if you are rendering with mental ray (and you want to have more control), or a simple spot with fog if you are rendering with maya software (and want less control and less render time too :)).
You can use portal lights as light cards if you want but I think that here a simple area light would do the same.
For caustics you have to use photons, but I guess you already know that :)

good work!

12 December 2010, 09:33 PM
Thanks Nookie! I do have Mental Ray, but ugh, it really is too powerful for me at the moment. I think im going to try the maya light method and see how that looks. Thanks!

12 December 2010, 11:10 PM
This is definitely a job for Portal Lights if you're using mental ray. Portals not only make for quicker lighting at rendertime (vs. using a ton of point lights, for example), but more importantly speed up and control the Final Gather coming from the outside lighting, which in your case should be a sun/sky node, despite the underwater-ness of the scene. Tweak the Haze to be green and your ground also in the physicalSky node itself, and tweak the color of your sunlight directional and/or your Portal Lights' color as well.

After that, the other two lights should be a piece of cake!

Edit: also, per the previous post, the volumetric light-scattering shader is simply "Parti_volume", not "mib_party_volume", in case you couldn't find it. This is another can of worms entirely though.

12 December 2010, 11:21 PM
Eheh u'r right :) i always spell it wrong :S

12 December 2010, 07:26 PM
Edit: also, per the previous post, the volumetric light-scattering shader is simply "Parti_volume", not "mib_party_volume", in case you couldn't find it. This is another can of worms entirely though.

Thanks Dark!

Can I plug in the Portal and the parti_volume shader into the same spot? The Custom Shader> Light Shaders?

12 December 2010, 09:28 PM
^^ No portal
^^Portal active
^^ Not sure why, but for some reason I'm getting these halos. I need to look at the geometry make better holes, appears as if the light is leaking through...

12 December 2010, 09:45 PM
To answer your question, I don't know how you'd connect Portal Lights to the parti_volume shader, but I'm testing it now. In the lights which affect the parti_volume, you put a "physical_light" shader into the mental ray "Light Shader" slot. This is where you'd put the "mia_portal_light" shader for volumetric lighting, but I don't know how you'd connect two shaders there.

One workaround could be to have two identical lights for each portal, one for the portal light and one for the parti_volume. Tweak their intensities so it doesn't blow the lighting out too much.

I'll be back with more info and some example renders for you in a bit.

Edit: As for your light-bleeding, this could be due to your Final Gather settings, but one way to test that is to go into your Portal Lights and increase then decrease the "Shadow Ray Extension". This basically is used to push the Portal Light's effects behind or in front of any glass window geometry. If that doesn't solve your problem, I'd move into testing Final Gather settings next.

12 December 2010, 10:49 PM
Here's with just a spotlight, using "physical_light" shader and parti_volume:

Same scene, with the spotlight hidden and an Area Light using the Portal Light shader instead. So far I cannot get the Portal Light to work with the Parti_volume shader at all, and turning on the regular spotlight has no effect. It would appear that using a Portal Light and parti_volume are mutually exclusive concurrently, but one could simply render a pass for each and composite them later. I'll keep trying.

12 December 2010, 03:09 AM
Thanks for the experimenting Dark :P
Multiple passes and Composting is totally doable, but I am very much interested in seeing your results, assuming you are still motivated by the problem.
^^Finally got the color close to what I'm looking for. Fixed the halos.

In the mean time, I'm working on how to light the pool and getting those shafts of light through the water.

12 December 2010, 03:51 AM
What about just throwing some particles in there?

12 December 2010, 07:05 PM
OK, I figure it out.
I created a bounding box, applied a lambert, in the shader's engine I plugged a transmat into the material and the shadow shader. Then a plugged in a parti_volume into the lambert's shader engine's volume shader.
It's rendering now (fingers crossed) I'll post and edit with an image once its complete. It's taking a long time to render, I'm going to have to make render layers and render in passes to make this work.

EDIT: Render Finished:
^^ It's gone wrong... 1hour and 7mins render time. But, we are seeing a nice atmosphere outside the portholes. :)

12 December 2010, 09:42 PM
OK, fiddled with the size of the parti_volume boxes size and realized it was too big. (Now its obviously too small, but this shows whats going on.)
^^So, we got the sky/physical sun light, its acting as our main light source with the help of a mia portal light and we have our crepuscular rays making their way through the dust via a transmat box with a parti_volume.

Now, how to clean it up?

12 December 2010, 11:14 PM
Where I left off, with only the volume spotlight:

Volume spotlight in conjunction with the Portal Light:

Some tweaking to darken things up a bit:

And increasing the volume samples to 8 and both lights to 16 shadow rays, as well as AA and FG quality higher, and a quick degamma:

Some FG splotchies, but the volumetrics look clean otherwise. Again, this is with two lights - one spotlight connected to the parti_volume setup (transmat cube, parti_volume in both shadow and volume slots) and one portal light connected to the sun/sky. It's possible to get clean results at least, just needs a lot of tweaking. All my sun/sky/portal light settings are super-low here, to avoid blowing out the lighting, and I even had to shrink down the portal light itself to help. Scatter on the parti_volume is at .6, and the spotlight is at 100 and linear falloff here. No photons, just FG.

Turning OFF the volume spotlight shows us what's really going on here, though:

The sun/sky directional light is working with the parti_volume unattached in any way, but the portal light itself appears to not be. Thus, the need for at least two lights. I'd also (ideally) turn off the sun's shadows altogether so they wouldn't conflict with the spotlight, but here you have it. Hope this stuff helps!

12 December 2010, 01:30 AM
Hmm, so you're not plugging in the sun into the parti_volume? But you are plugging in the spot light and the portal light. And the spot light is in front of the portal light?

12 December 2010, 01:47 AM
There is nowhere to plug the sun/sky or the portal light into the parti_volume, that I can find. You get one "Light Shader" slot. Only the spotlight is plugged in. I don't know why the sun/sky directional light is interacting with the parti_volume. There are no lights linked manually here in the parti_volume, and it shows a 0 when you roll out that section in the attributes.

In this scene, the portal light is slightly behind the spotlight, and rotated to fit the opening, whereas the spotlight is pointing at an angle. One could easily line up the sun/sky directional light to match the spotlight of course, but I didn't do that in these tests.

12 December 2010, 04:34 AM
Open your attributes to your parti_volume, scroll down to Light Linking and then to Lights there you plug in your light. This is the only way I know to use parti_volume, yet you're getting the effect another way. I'm confused.

12 December 2010, 06:37 AM
Oh yes, I'm aware that you CAN link the parti_volume to lights through its own node-slots, my point was that lights themselves appear to only want to connect to one shader on their end. I assumed it was to prevent overlapping or conflicting results.

Thus, I have not connected my sun/sky directional or area light to the parti_volume, because I thought that this would break the connection to the physical_sky (directional light) and the mia_portal_light (area light) respectively. I'll test tomorrow to see if they can share outputs with the parti_volume as well.

01 January 2011, 08:53 PM
Thanks for the help, Dark.

Ive been busy with other projects atm, modeling stuff.

Still have this on my mind tho, still working on it.

How do i control the amount of photons being emitted by the portal light? Seems as if im not getting enough in. Granted the light source isn't all that power full, but its evident that im getting rather splotchy results, i don't wanna crack up the FG if i can help it. Render times are already terribly long. 20 mins with just lights, the wall with the ports cut out and the parti_volume.

01 January 2011, 12:34 AM
floze tutorials (

this should help. u might not need gi and photons it might be over complicating it. for volume u could even get away with a separate maya software pass with a shadow map light. i would start blocking out your textures,shaders and camera. turn on ao in your mia shader, put a key coming through the window, turn on final gather and increase you ambient tint in the shader to about 30% and you should be 90% there. for water try the mental ray ocean shader in the displacement/bump. tint the refractive color to cyan or blue. put a value like 5m or something in the refraction depth and fade it to a darker color to create the illusion of depth. hope this helps. :)

01 January 2011, 06:45 AM
I'm with Patrick on this one. I'd only use photons, caustics, and GI if you absolutely have to. Not that they don't rock, but they're a bit unmanagable compared to straight FG. You'll take a slight performance hit (slower renders) but they'll be much more predictable. I tend to save GI for projects when I have some extra time to play with 'em. There's nothing physically accurate or intuitive about photons in mental ray, especially for Maya. It becomes guesswork.

You can generally take it 95% of the way with just FG alone. Some people use Importons and IP, but I don't yet. If you want to try those methods (which are even newer and less supported than FG) there's plenty of awesome renders, results, and threads around that deal with those, but I've never seen anyone use Importons or IP with the parti_volume shader yet.

01 January 2011, 10:23 AM
tbh you dont even need fg if you add the bounce and fill lights your self but fb might look nice for subtle bounce. the ambient and form can come from the mia shader(ao) the rest with lights if you go this way u can use very low fg settings and let the shader do most of the work. for cautics just render out a image sequence from a caustic generater plugin (free online or maybe tinderbox?) and use it as a gobo in a light. if you want to have different textures for the under water bit different colors/grim etc. just use the rayswitcher in the diffuse and then in the refraction part of the rayswither add in the different texture maps. rendering/lighting isnt all about physically correct an raytracing.your render times will be much less and you will have more control if you keep to simpler old school methods,cheats and hacks ;-) hope this helps :)

hey InfernalDarkness
i like your volume renders they look cool. i have never used that shader but looks like u can get some nice results.

01 January 2011, 06:51 PM
Thanks guys!, GI and FG were killing me, these new ideas will make this much easier. I'm going to read up and rebuild my scene. \

01 January 2011, 10:50 PM
hey InfernalDarkness
i like your volume renders they look cool. i have never used that shader but looks like u can get some nice results.

They're just quick tests to help out our buddy here. Nothing special - that's the only volumetric lighting shader there is for mental ray currently, the parti_volume shader. If you're using mental ray, you're stuck with it.

01 January 2011, 02:42 AM

Heres what we were getting with parti_volume setup:
That took 4 hours and 44mins^^

Removed the parti_volume and turned on FG and got this:
That took about 20mins^^

Water isn't working. I have set a transparency and translucent-ness yet its still not transparent. Glow is obviously too blown out. I haven't applied any lights in the pool yet, just have an ambient cyan color and with FG on, its emitting light, sort of. I'm lost as to how make a believable water.

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