Rendering in Pieces

tanka

Hey guys, I'm in the process of modelling a high poly tank. At the moment, my treads are increasing the polycount by quite a large number, and mental ray refuses to render the scene.

I figure I have two options, one is to redo the treads, and model them more efficiently (which probably isn't a bad idea). The other is something I have heard about, but cannot find much information on; and that is ofcourse rendering in pieces.

Does anybody have any information on how to effectively render a scene in peices and composite them later on? Are there any tricks to it? (preferably in maya)

Thanks in advance.

renderhjs

if you are rendering with GI it almost impossible to render in pieces without a resulting render that has some flaws in the shadows and shading of the GI photons.
In my past I had mental ray failures because of to big textures but never because the scene was to complex.
Have you tried setting up the clipping range in the viewport which most likely will affect the rendering as well. Other things that come to mind are using the satelite rendering across a few computers or digging into the advanced rendering options (where you can setup the distrubuted bucket rendering stuff).

Firebert

Do you mean render in layers?
Are you absolutely sure it is your treads? Have you troubleshooted this item specifically? Are you sure it isn't a specific shader you are using? Maybe you're BSP setting needs some adjustment. Run a render diagnostics to see what initial errors it returns.

Mark Dygert

You might want to render in passes instead of rendering different chunks. For example, render a diffuse/color pass, then apply the MR/AO material and render out AO shadows, then render dominate light/shadows, then a depth pass and composite those layers instead of trying to render everything at once.

Also check and make sure you're using lights and shadow settings that MR plays nice with. Enable the error report window will show you any problems.

tanka

It's weird.. I've since split up the tracks to see if it will render, I've even tried rendering one peice of the track, and it just won't render, Mental Ray comes up with a fatal error, and Maya Software comes up with a memory exception. The track pieces on their own aren't very hi res. I've changed the texture aswell, but it's still happening.

/edit. This is really annoying, whenever I render with maya 8.5 on my new PC it always throws memory exceptions. My old PC running maya 7 never had these problems. I've been toying with the memory limits but the results are mixed. What is this BSP thing I keep hearing about?

glib

BSP tuning will help your speed, but it won't solve crashes. Mental ray fatal errors seem to be dark voodoo magic more than anything else.

Export to a new scene, restart the computer and sacrifice a goat.

Firebert

I have tuned my BSP (as well as the method) before when memory was running tight and it fixed it. It would take much longer to render, but it wouldn't crash from lack of memory. Read up on BSP here.

BSP is not your issue here though. I would select all of your objects, assign the default lambert shader, open hypershade, delete all shaders, shading groups, and textures. If you have a light setup, delete that as well. Assign everything but one single tread to a new display layer and turn off the visibility. See if that will render.

***** Oh, something else, since you are rendering in mental ray, are you displaying your model at the lowest division? When you hit "1", "2", "3", you move from lowest, caged/smoothed, and smoothed previews. Maya Software will not render out the smoothed version, but MentalRay will if you have it active in your viewport. The problem may be that you are trying to render in MentalRay, and it eats up so much memory that Maya Software can't even function even though MayaSoftware is more CPU based and MR is heavily RAM based. I can't remember if preview smoothing & rendering was available in 8.5 or not...

Try exporting one tread with the default lambert shader as an .mb file and open that to see if it will render.

Each time you get a memory exception or some crap, you have to at the very least restart Maya to free up as much memory as you can without restarting your computer. If you just leave Maya open and keep trying to fix this each time you have an error, you won't get anywhere.

Maybe just take the time to model out a simpler version of the tread and use that with maps for detail?

tanka

I just downloaded SP1 for maya 8.5 and now I can render more than one tread at a time. I think the treads are just too high poly, so i will go back and correct them. My biggest problem before was that Mental Ray wouldn't render one tread on it's own, they didn't have shaders, there was only a default light in the scene. It was as bare bones as things get. It will do that now, so I'm happy.