Basically, I don’t know of anyone who renders a full scene only using one layer, this is especially true for effects. All the complex effects you see in the movies are done in several layers and these layers are then comped together to get the final effect. This allows for more control over the final look and keeps render times down.
Lighting Maya Fluid System
govindk
#22
Yes I have heard Wayne telling that in his tutorials…
This however is something I wanted to test personally, just to see what happens…
Duncan
#23
fume fx has an option of light-linking.
I don’t understand when fluids is such a HUGE area in Maya’s dynamics, not having a option like that. Then all this fuss over lighting can be avoided right?!
I just tested and light linking for fluids is working for both Maya sw and Mental Ray. (at least in Maya2012) In the relationship editor make sure that you set the linking on the fluidShape directly, not fluidShapeSG. Let me know if this doesn’t work for you.
As mentioned avoid any ambient lights as well as any non-shadowed lights with fluids as these will then penetrate the volume and make it glow. Volume renders are dependant on shadowing as opposed to surface rendering that uses the surface normal for lambertian shading (which is really a trick where we fake subsurface scatter shadowing). As well self shadowing on a volume is expensive and the computation is proportionate to the number of lights, so keep the number of lights on the fluid to a minimum.
One other point is that mental ray lights require that raytraced shadows be enabled on a light for the fluid to self shadow with that light. With the maya sw render lights will self shadow on the fluid if the selfShadow toggle is on, regardless of whether shadows are enabled on the light. The mental ray implementation allows you to have some lights that self shadow on the fluid and others that don’t while the Maya implementation allows you to have lights with depthmap shadows (for other objects) selfShadow on the fluid (the selfshadowing is still a raytrace self shadow).
For the fluid when real lights are ON it still applies the ambient brightness and color as defined on the fluid node. Set this to zero if you only want the scene lights. However you might find the ambienDiffusion(mental ray only) is useful for simulating scattered ambient light, particularily if the fluid is quite dense and opaque.
govindk
#24
WOW, help straight from the TOP… :bowdown:
Thank you so much Duncan for replying…
I avoid using ‘ambient light’ for anything I do, as much as possible. But I do have some non-shadowed lights that are linked to illuminate certain geometry in the scene. I was wondering how to disconnect them from illuminating the fluid within the container. I tried what you told me to do, but I did not see the container option inside light linking relationship editor (a screen shot is attached with this post), but only fluidShape1SG. Duncan I am using Maya 2011 sp1 student version. I haven’t tried that in Maya 2012 though.
'cause in future if I light a scene and I would do fluids inside the scene, it would be much easier if I could to light linking for fluids.
I don’t mind doing the composting work, but at least I will have a base lighting to start with and have good starting point to color correct.
Duncan
#25
It seems that in versions earlier than 2012 you could not drill down to the fluid shape in the light link editor. Thus as far as I can see you can’t use the link editor in 2011 to manage fluid light linking. However the make/break links menu items still work OK. Select lights you don’t want to shine on the fluid, along with the fluid and do “lighting:break light links”.
Duncan
govindk
#26
Good lord, I thought if light link relationship editor didn’t show it then this option won’t work at all… :eek:
DUNCAN IT WORKED… wow…
thanks a lot. :bowdown:
AWESOME !!
govindk
#27
Duncan,
I recently switched to Maya 2012 and like you mentioned I did not find fluidShape in Light Centric window for unlinking the light…there was only fluidShapeSG…
If I expand fluidShapeSG I get fluidShape inside it, but I am not able to select it in any way.
(Image attached)
However the make/break light links does work. However since you said it worked in a test you did, I was curious why I am not able to use the option.
DDelapena
#28
In my opinion the best way to light fluids is a generic at minimum 2- at most 3- point lighting pass, the key light being the brightest(value of 1 is usually sufficient). This really depends on what direction the key light should be coming from. To composite, create RGB layer overrides on all 3 lights, one being red, one blue, one green. Blue can be the rim light, red the main key light, and 2 can be the fill light.That way you then have complete control of your fluid lighting in comp. Asssuming you know how to key the R G or B values. Color correct as needed. Also, be sure to atleast render out a 16bit float image…If it’s 8bit, the color correcting values will be limited and your fluid is most likely going to become flat. Careful when you set your settings to 16bit, if you continue to render a normal tif, or iff file, it will not actually be 16 bit. it needs to be type EXR, or uncompressed TIF. Render in Mental ray with ray tracing turned on. values of 1, 1, 2 is fine. For quick testing, set your aliasing to 0 and your fluid quality to 0.55. ( I actually end up keeping it at this setting because with quality too high it looks too smooth at times, I like the noisey feel)
Set real lights on, your self shadow depending on how light or dark u want the shadows. If you want them to have color, turn segmented shadows on and change the color of your shadow on the light. (render time takes awhile, but results are usually fantastic when enough shadow rays are set. One thing i do notice is that the fluid doesn’t really respect the light angle of the light when casted on the fluid itself. On geometry, it’s fine. It’s always usually a hard edge on the fluid itself… =\ Duncan? 
Also, the new lighting attributes included in maya 2012 makes this process a lot easier with the ambient lighting options. Love it Duncan. Keep improving that fluid container.
thanks
-Dan
DDelapena
#29
Oh yea by the way,
Usually directional lights with ray tracing shadows turned on does the job for the RGB passes.
govindk
#30
Thnx for help Daniel…
I haven’t reached that far with fluids like you guys. I am still learning. And I am really itchy while using fluids, 'cause I get really hard edges in my smoke even though I make the opacity graph like a slope…and lotta other small bad looking things like that.
Nope, I don’t know how to take RGB passes, but I did know you could. Just waiting to learn it slowly. If you have an link on how to do it, I’d really appreciate it if you post it here.
Actually I make a single directional light with raytrace shadows and I un-link it from my scene and link it only to my fluid. And un-link scene lighting from fluid using make/brake light link option. It seems to work for me.
By the way, I’m curious, what option where you mentioning to Duncan…?
I didn’t find any differences in Lighting Option under “lighting” on fluidShape in Maya 2011 and Maya 2012 :surprised
PS: loved your flame thrower
DDelapena
#31
IMO, the best way to avoid hard edges is to keep the first point at pos=0, val=0. 2nd point pos=1, val=1 in the opacity graph. Then set the first point to smooth interpolation. If your fluid disapears, set your input bias up a bit between .25 and .5 depending on how much density is involved. This will you give a fantastic smooth and soft fluid look to your smoke/dust. Not recommended for fire. :)
Also, as for RGB pass. There’s multiple ways to do it. One way, is as easy as setting up 1 render layer. Adding the fluid and turning on real lights. Setting up a 3 point lighting system with 3 direction lights. 1 red = keylight, 1 blue = rim light, 1 green = fill light. Render. Now you’ll have RGB in 1 pass. In comp, just channel out the R, G or B as a matte for color correcting the 16/32bit float image.
2nd way (my personal favorite), set up 3 diff render layers. Name one Red, one Green, one Blue. Add fluid with real lights on in each. Add each light respectively to each colored layer. Render. Now you’ll have 3 diff renders with each pass separate. Personally i find i get more range this way… but both work. If you don’t know how to channel out the R, G, or B, then here you can channel out the luminance values since they are all separate. And use as a matte for color correcting the 16/32 bit float image.
hope this helps!
-Dan
tozger
#33
I agree with DDalepena and this is how I use at my studio I work at also. Most of the time I try to use three lights.Key , rim and fill then I use these three lights as red green abd blue which helps for the comp guys to use as masks.
Also if render time is no concern I make the incandescence to zero to render only the smoke then another layer with smoke as real black to give more control to the comp guys as fire and smoke separate.
stooch
#34
i can raise it up a notch…
instead of making 3 new render layers, create 3 custom color passes, then create 3 color output buffers in hypershade and pipe your colors into passes, each buffer node will then let you specify which pass you want to link it to. You can control where the render pass outputs by editing your file name prefix to include: <RenderPass> in it.
This is better than render layers because they will all be generated from the master beauty pass. So they are essentially free, if you have 3 render layers, that is maya batch performing 3 separate renders, along with all of the computation that involves.
All this can be easily scripted.
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