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Just some quick questions about Maya lighting and mental ray bake....


King Bright
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Ok hey all :) 

 

I just started to study 3d-design, but at the moment im learning all the ways to model in Maya 2012... and lighting and baking (especially uv-mapping) is about half a year for me to go from now... but i just want to ask u some quick questions.... would be cool when somebody could answer me some of them...

 

I wanna start creating prefabs and furniture (maybe also clothes but later ^^ ) the modeling of them all is what i already know how to do... but my problem is just, when i add lights and surface-light-materials to bake shadows it takes crazy time to calculate and render the texture... ambient occlusion goes inbetween 1 minute on a 2048x2048 map from a whole building.... and it already looks nice (i only need to figure out some uv-mapping issues cause of the seems i get...) but as soon as i want to bake global illumination, light only or light & color it takes too much time... about half an hour for only an single wall segment to bake to an 512 x 512 map... so my questions are:

 

how do u set up your lights?

how many? and wich kind of light? and wich settings you use for the lights and the mental ray render settings like fg / gi / ao....

 

oh and when i try to rotate the sunlight, it just turns to black ^^ dont know why this happens... but its confusing :-(

 

oh and which is the best way to bake textures? should i bake ambient occlusion and an light only map to merge them both in photoshop? cause thats what i often read... but theres still the problem with the light only baking, cause it take a lot of time but still has a very poor output... and how can i get the textures i added in maya to my baked maps? or do i have to use the bake light & color option? 

my pc specs are: amd fx 4100 ( 4 x 3,6 (turbo-mode 4 x 3,8)), 8 gb ram ddr3 (1866), ati hd6870, and i have win 7 64 bit

oh and before i forget to say: i have the trial of maya cause i get my students full version on 3rd march... i've read something like the trial is only 32bit but will it reall change so much in render time with the full version?

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The best and fastest renderer for what you're looking to do is Turtle.  If your copy of Maya is part of one of the Creation Suites, Turtle wil have come with it.  If it was just Maya by itself, then unfortunately, you won't have Turtle. 

(When Autodesk bought Illuminate Labs, maker of Turtle and Beast, they discontinued Turtle as a stand-alone product, a decision that made absolutely no sense to anyone.  That's one of the biggest reasons I still have not upgraded from Maya 2009.)

If you dont' have Turtle, you can get just as good results from Mental Ray, but it will take longer.  Mental Ray has never been any danger of wiinning any "world's fastest renderer" awards, but it can produce fantastic looking results, as long as you're patient with it.

That said, there's no reason it should take half an hour to bake out a 512x512 from a flat plane.  Something in your scene must be borked.

You've asked a lot of questions about lights, but I notice you don't seem to be factoring your materials into the equation.  If you're using POV-dependent features that do not translate well to baking, like sub-surface scattering, volumetrics, deep reflections, refractions, etc., you can slow things down to a crawl pretty easily.  I'd look to that sort of thing as your bottleneck, before I'd even think about your lights.

As for questions as worded:


King Bright wrote:


how do u set up your lights?

how many? and wich kind of light? and wich settings you use for the lights and the mental ray render settings like fg / gi / ao....

There's no way to provide a blanket answer to any of these questions.  How I set up my lights depends on what's in my scene, and what effects I'm looking to create.  There can be no such thing as "how to light your scene for baking in 10 easy steps."

If you've got a specific scene, and a specific effect you're trying to create within it, that's something we can answer how-to's about.  But just broadly asking, "How do you set up your lights?" doesn't work.

It's like asking, "How do you cook your food?"  There's no way to provide a worthwhile answer, since the question is obviously way too broard.  But if you were to ask something specific, like "How do you cook a spinach souffle?" you could get tons of useful answers about that particular subject.

 


King Bright wrote:

oh and when i try to rotate the sunlight, it just turns to black ^^ dont know why this happens... but its confusing :-(

Please explain what you mean by "sunlight" in this context.  Are you using Mental Ray's sun and sky system?  Or is this a light you created yourself?  Something else?

Also, what turns black, the scene, or the light itself?

 


King Bright wrote:

oh and which is the best way to bake textures? should i bake ambient occlusion and an light only map to merge them both in photoshop? cause thats what i often read...

Once again, it depends on the specific needs of your project, and also on your own personal style. 

Some people prefer to render each surface attribute in a separate pass, and then combine them in Photoshop afterward, because that approach affords an extra degree of control.  You can adjust the intensity of each element via layer opacity in Photoshop, and if you decide you want to change a particular element, you can re-render just that element, vs. having to do the whole thing over again.  Also, if you're creating for a platform with a better graphics environment than SL's, you may be able to connect each image to a separate channel in the in-game shader system, for much better effect than just the fully merged bakes to the diffuse channel that SL can handle.

On the flip side, some people prefer to get everything exactly the way they want it in Maya, and then render everything out to a combined texture, all in one go.  That's  can be much faster and less labor intensive, as long as you're sure you've got it right the first time.

I do either or both, depending on the project.

 


King Bright wrote:

but theres still the problem with the light only baking, cause it take a lot of time but still has a very poor output...

By "light only" I assume you mean you're just rendering light and shadow, with no color or other attributes.   That should be super quick, even if you've got a complex lighting setup in the scene.  If that's really taking a long time, then I'd again have to suspect something funky is going on with your shaders. 

If that's not what you meant, please explain.

 


King Bright wrote:

and how can i get the textures i added in maya to my baked maps? or do i have to use the bake light & color option?

If you're not baking color, you're not going to see anything from the color channels of your shaders.

 


King Bright wrote:

oh and before i forget to say: i have the trial of maya cause i get my students full version on 3rd march... i've read something like the trial is only 32bit but will it reall change so much in render time with the full version?

I don't see why they wouldn't let you try the 64-bit version.  I haven't had cause to download a trial version in almost a decade, though, so I couldn't say for sure.

If indeed you've been using a 32-bit version, that could go a long way toward explaining why things are taking so long.  By definition, 32-bit applications can only use 4GB of memory, including graphics RAM and system RAM combined.  If that HD6780 has 1GB of video memory, that only leaves 3GB of system RAM available to the program.  The 32-bit verison of Maya reqires 2GB, just to run, which means you've only got 1GB of overhead.  That's not much.

64-bit applications, on the other hand, can use as much RAM as you can throw at them.  The limit is a hair over 17 billion gigabytes.  To build a machine with that much RAM, you'd need about 2.2 billion 8GB RAM sticks.  Considering that they tend to be spaced at roughly a half inch on center in most motherboards, you'd need a motherboard about 16,000 miles tall, to fit that many sticks in it.  So, the top of your computer tower would be in outer space.

So, yeah, there's just a wee bit of a difference between 32-bit and 64-bit.  What it means in the machine you've got is that Maya would be able to to use the full 8GB of RAM, instead of just the 2-3GB it's currently stuck with.  That would likely translate to a huge difference in render times, not to mention every other area of performance.

 

Now here's the bad news.  The student version of Maya puts a watermark in every rendering, including bakes.  You won't be able to output any usable imagery from it.

If you want to use Maya for anything besides student projects, you're going to need to buy it.  If you can't afford it, I'd suggest you start learning Blender.

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Okay and another long answer to follow the above by Chosen Few. Since he already answered the most in a good way let me go into some of the unanswered:

- to bake shadows it takes crazy time to calculate and render the texture...
- how do u set up your lights?

Shadows are depending on your settings raytraced / raycast. And also depending on the amounts that are set for gathering and samples it can take up quite some time to be rendered. And of course the more lights you have in a scene the more shadows and nuances of them it has to render and keep track of. 

One thing to keep in mind when setting up lights: not every light needs to be set to 'cast' shadows. Just as in nature some lights are just so called 'rimlights' or highlights which are only used to achieve effects from the real world with lights that bounce off from surfaces or are gathered very strong at a certain spot etc. - Ergo: don't cluster your scene with shadow emitters. Check which lights really need to be set to cast shadows and which are not. 

Have a kind of all-around working lightset in mind when you set up your lights. As Chosen Few already said there is no absolute rule and for sure no 'always working light setup'. 

Think about the environment your object would most likely be in ( a car = outdoors - aka an evenly distributed sun / sky environment would be preferable here, or a furniture = indoors- a few lamps and eventually lights from nearby lamps when you know where those would be in a scene / house - otherwise just choose a setting with a brightness similar to a house environment. Which is mostly 1 or 2 Lights from above and some Windowlight. Or when its the skin of an avatar a kind of studiolights setup mostly works best. And so on.

Also keep in mind that SL has shadows and some skylights, and object lights. If the user didn't need to disable them or if their outcome is blocked by huge prims in the sky. You really don't need to add what's 'already there' or if you do so then in a lowered fashion so that it would cover both scenarios (with shadows/lights and without). 

Also the 'renderer' you are using can make big differences. (like the Turtle renderer Chosen suggested to you, Or Vray for awesome illumination effects with a very optimized rendering time.)

Look at real life pictures of objects in similar scenes to get a good feeling from where light comes, how strong, where actually shadows are produced and where they are so sottle that you barely will need to recreate them for a texture bake.

In general as soon as we leave the AO only sector rendering will always take longer. If you have ever seen how long a fully rendered image can take when it is supposed to have real life quality and lighting then you know what we are talking about. It can take up to several hours depending on your lights, settings and materials, postprocessing filters, shaders and so much more.

Rendering in passes is also one way to achieve shorter rendering times. (just define which pass to bake and then combine in photoshop or gimp at the end.

As chosen already assumed - I can confirm this: there is a 64 bit student version of Maya already for Maya 2010 and upwards. But yeah the watermark will make outputs rather unusable and you should overthink if you don't want to swap to blender. The earlier you start learning another program the better. Rather then spending lots time on one where you figure in the end you can't afford it and have to start over again.

Cheers, Code

 

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