Lighting Maya Fluid System

#11

Do you have a lens shader attached to your camera? if so. Set gamma to 1.0 or leave at 2.2 1.8 etc. and set you lights to quadratic falloff. adjust intensity accordingly. this will also affect you colors (the would need an inversion of the gamma correction if you set it to 2.2 or 1.8.Obviously your directional light won’t have quadractic falloff but the others will.You could also try using MR lights instead. They will force quadratic falloff.

#12

I checked ambient light is 0.00 in fluid’s lighting tab
default light in Maya is unchecked but I do have a lens shader

“mia_exposure_photographic,” to my renderCamera but not to perspective, from which i rendered the above images.

settings of the lens shader, I have attached as an image.

I will look into what you have suggested once again and let you know

Thank You

#13

Well you shouldn’t be getting the results you are. I always render with MR and it comes out fine. Just going to have to double check everything. Self Shadow. Shadows on lights. lens nodes. Are you using FG? You’re photographics shader is set to the default gamma. set it to 1, render with that and see if it looks better.

#14

Rochre I am not using the lens shader in Persp Camera but a in renderCamera.

Persp is where I am rendering for the tests, does that lens shader affect then?

#15

No lens shader shouldn’t be conncected to your perspective camera. The only time a lens shader would be connected to all your cameras would be if you had create a sun and sky system. Howeever if you plan to be rendering out of a camera with a lens shader then that’s probably the camera you should be basing your final look on. That said. I’m plum out of answers for you. Can you post the scene file?

#16

No lens shader shouldn’t be conncected to your perspective camera. The only time a lens shader would be connected to all your cameras would be if you had create a sun and sky system. Howeever if you plan to be rendering out of a camera with a lens shader then that’s probably the camera you should be basing your final look on. That said. I’m plum out of answers for you. Can you post the scene file?

#17

Ya I am aware about the MR Sun & Sky.

Rochre, the thing is I am sure all this effects are color corrected done more justice in post, becuase Wayne keeps emphasizing on post on his DVD, he tells the sim has to look good first (priority); And then you go do all color corrections and add things like Motion Blur in post …

Even though I know we can do it in post, my doubt, I should rather say CURIOSITY…about how these pros in VFX comp a fluid into the scene and match the lighting without a flaw, I mean you still need a good base lighting to edit in post.

I think I should make my query more transparent, so here goes.

  1. How to light a fluid to match your scene lighting. Even if its color corrected in post there has to be some lighting done to match the scene. How many lights to use or at least a good starting so the fluids won’t render flat shaded. Sometimes turning of “real lights,” gives awesome results, not to mention playBlast, often looks so cool.

  2. If it’s not dependent on post then how to un-link the scene lights from fluidSystem to it won’t render flat.

  3. After rendering in Hardware render buffer (hrb), Mental Ray & Maya Software render renderer
    Mental Ray and HRB is giving the best results (at least to my tests). And some HRB is way to cool but can we use it? in final shot? do they use it?

Now to some people this post may seem noobish, but this something I face almost all the time cause I always do sims on a good lit environment. So I am really curious.

By the way Rochre the scene file has been attached to the this post, do check it out and let me know. And thanks for all the help mate.

Gov

#18

I’ve taken a look at your scene file and there are a couple things you can do. First I’d like to tell you how I render and light fluids. All my fluids are rendered as separate elements that I then composite back into the final render using a composting program. When I light a fluid I try to fake as much of the lighting as possible. You don’t have to match it perfectly.

Fluids are lit a little different that geo. The main difference is shadowing. The reason you have flat shading is because the majority of you lighting is not casting shadows. A light that does not cast shadows completely penetrates your fluid and illuminates all parts of it equally. I would start with one keyLight that is casting raytracing shadows. Always start simple. My typical lighting set up consists of one direction light casting shadows and one ambient light, which is used as a base luminance. If I need to add more shadowing detail I can add another directional light to highlight the areas that I want to see. (again casting shadows.)

Your scene basically has a moon light that is your key light and a backlight being cast from your lamp. Basically you can set up a directional light for you moonlight, and ambient for fill lighting, a secondary directional for some highlights, and a point light with falloff for your lamp. That should give you the basic lighting you need. Then all you have to do is composite the images together in aftereffects or nuke with mattes, holdouts, and shadows.

#19

Hey Calibrix,

           Yes I actually did something similar to your suggestion and I got this - http://vimeo.com/31217152

I mean two Dir-lights and one point-light, a basic three point lighting setup.

So i guess my doubt is clear regarding this.

*** COMPOSTING is the best way to match fluids into a scene, and do the tweaking on NUKE/AFX or whatever***

Great… :beer:

Thanks to all who took time to reply. Appreciate it :bowdown:

#20

Please don’t feel I am comparing or being biased but

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?!

Well there must be a strong reason why they don’t have it, but who cares Maya rocks anyways. :slight_smile:

#21

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.

#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…

#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.

#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.

#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

#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 !!

#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.

#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? :slight_smile:

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. :slight_smile:

thanks

-Dan

#29

Oh yea by the way,

Usually directional lights with ray tracing shadows turned on does the job for the RGB passes.

#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. :slight_smile:

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