How does mental ray handle heavy geometry scenes ?

[paraganek]

Hi Mental Ray gurus,

 

I am in a process of comparing Vray and Mental Ray renderers and I am trying to find out how good (fast) Mental Ray is in handling and rendering really heavy geometry scenes.

In Vray we have been rendering large exterior scenes with 3D high-poly trees in full GI using vray proxies. A typical scene is about 500 trees each about 400,000 polygons which makes a 200 million poly scene.

Does Mental Ray have anything comparable to Vray proxies to be able to render such high poly scenes? Is there maybe any other approach in mental Ray to handle such a heavy geometry?

 

Please share your knowledge :-)

Thanks

[manta]

Nope, it will crash, vray proxy's are the greatest invention ever, I don't think any other renderer has something similar, that will change I'm sure...

[psv1]

use placeholder objects.....

 

F1 in max should bring some light too on that matter

[AJLynn]

You've got Vray handling 200 million polys? I'm impressed. But maybe there's a better way to handle your trees - 400k is a heck of a lot, unless they're your subject matter and you're doing close-ups of them.

 

The most complex model I've worked on recently has all of downtown Boston, and that's 429k faces.

 

I know mr has an Instance function but I don't know how/if that works well with Max. And mr's GI calc time is pretty much geometry independent, so if you can get it to load you should be able to render it.

[Christopher Nichols]

dude... using instancing I have been able to render a few BILLION polies in Vray using only 256k of ram.

 

 

if you look at the computer and the version of Vray you will see that it was a LONG time ago.

[manta]

Ya, I was gonna say thats nothing also (200 million) I've rendered 15,000 high poly trees (200,000 polys each) and my computer didn't even flinch, took like 4 minutes to render with GI, love proxys...to tell the truth I don't know what the actual limit is, I never reached it.

[AJLynn]

Wow. I had no idea. I'm going to have to try this.

 

Does it work well with large models (say, a large city) or just with instancing? I've been fighting with a model of downtown Boston for months...

[manta]

yes, you can convert large sections of your city into vray proxy meshes, and then just import them into your scene...

[pradipta]

It's an very important aspect of vRay rendering. Do you have a proper article on vRay proxy and it's use? I have been looking for it for a long time. would be grateful to you for helping me out

[Karlfucious]

Acually Mental Ray will render any size scene without problems when you use large BSP. It renders about 15% slower than regular bsp but it should be able to handle billions of polys without any crashes.

[manta]

Sorry, I stand corrected, just did a test, and MR did not crash, however it was using alot of memory 1.4gigs, it also took 42 minutes to render, in contrast the vray scene with proxy's took only 1 minute, and used about 400mb of memory,

 

So the moral of the story is if you got the time you don't need vray...

[nisus]

Hi All,

 

Where can I find information about the MR placeholders and the workflow to render large amount of geometry?

 

rgds,

 

nisus

[tecton3d]

final render stg1 has some features for complex geometry as well. Although I've never pushed it, it sounds promising and similar to V-ray. Has anyone out there been able to compare these features in a face-off?

 

On demand loading

finalRender Stage-1 offers an "On Demand Loading" feature that will only load 3D objects into memory when needed (seen) by the raytracer. This feature alone can save an enormous amount of memory for the raytracer while processing large-scale scenes.

 

Memory Pool Recycling

Besides this nifty scene management, finalRender Stage-1 also offers a mode where the user can "lock" the amount of memory that should be used at all times regardless of the real amount needed to render a scene! A user could decide to keep only 25 objects in memory and nothing more. If the raytracer needs more memory, the least important 3D geometry is unloaded from memory first, and then the same pool of memory is reused. This will make sure that no extra memory is allocated.

 

Advanced Proxy Stand-In Loading

finalRender Stage-1 even goes one step further in handling large scale scenes! By directly accessing the renderer core, one can use zero face, zero memory objects that will be later swapped with high poly meshes at render time. Then, after rendering is done, this mesh will be fully unloaded from memory giving more space to other tasks.

[antonio_frias]

Hi Mental Ray gurus,

I am in a process of comparing Vray and Mental Ray renderers and I am trying to find out how good (fast) Mental Ray is in handling and rendering really heavy geometry scenes.

In Vray we have been rendering large exterior scenes with 3D high-poly trees in full GI using vray proxies. A typical scene is about 500 trees each about 400,000 polygons which makes a 200 million poly scene.

Does Mental Ray have anything comparable to Vray proxies to be able to render such high poly scenes? Is there maybe any other approach in mental Ray to handle such a heavy geometry?

Please share your knowledge :-)

Thanks

 

I'm curious, just how do vray proxies work?

[nisus]

Hi,

 

I have asked the same question before... But no one can tell me more (about MR placeholders...)

 

 

rgds,

 

nisus

[Karlfucious]

Im not too shure because im not a Max user but in Maya you can just use instances. Im shure Max has something simular but I wouldnt know what they are called.

[manta]

I'm curious, just how do vray proxies work?

 

Vray proxies are meshes that have been coverted into a vray mesh object, it is no longer a 3d max object and will only show up when rendering with vray...

and are only present in the scene, represented by a placeholder, they can not be animated, such as a charactor walking or a tree blowing in the wind, but their position, rotations and scale can be animated...

 

Material mapping is done by applying the materials from the orignal object...

[juanmolina]

have a look at

 

http://www2.festival-gmbh.de/sixcms/media.php/108/TipsUndTricksZuMentalRay_ThomasDriemeyer.zip

[Wreck]

Hey guys...

 

I'm using V-ray and we import about 7 proxy buildings, nothing really that harsh, and it crashes the hell out of this machine.

 

it's a Quad. Two 2.9ghz and Two 3.ghz processors, a Quadro 4500, and 4 gigs of ram with the 3gb switch on.

 

Vray falls apart and I'm talking about a scene with no trees, no textures. The scene posted above with all the trucks must be at least 50x's my scene.

[manta]

Does it crash on import or when you render...

[Wreck]

On render. We get our scenes imported fine, it's pretty heavy in the scene despite that we're using proxy's. We hit render on a small 1200x700 render and it gets halfway through calculating the light cache and it bombs. Gives a V-Ray Memory Acception error.

 

We turned raytracer off and we got further but if we then add more to the scene it has the same issue.

 

We then decided to test scanline vs V-ray in the scene and Scanline rendered it ok.

[manta]

Hmmm...what are your light cache settings, better yet set everything back to default, you can do this by selecting another render engine, and then reselect vray, this should put everything back to default, and see if it renders without GI, then turn GI on, but don't touch the settings, if that doesn't work we'll try something else...

[Wreck]

I'll try it first thing monday morning when I get back into the office. I'll post back in here as soon as I try it out. Thanks. I figure shutting things off will work but shuttin' GI off is gonna suck

[manta]

Well, we're only shutting things off to narrow down where the problem is, you may have accidentally raised one or more of the values way too high, if it still crashes at default values, then its not the GI at all, I would think maybe a geometry problem...I have rendered billions of poly's with high GI settings with no problems, so I know it can be done, we just need to eliminate possible problems to find the real cause...

 

Do you have any materials applied to your models yet ?

If so, there is a material over-ride in the Vray dialog, which will give everything in your scene a simple vray material, so if it crashed before using this, but didn't after using it, then you know you have a bad material in there...

[nisus]

Back to the original problem... MR handles large geometry very well. The problem lays in max... The way MR is implemented in max now, Max will ALWAYS load all the geometry in memory... thus resolving in a crash.

The only way to avoid this I know is to trim down memory usage wherever you can (Best to do this always, btw)

 

and maybe rendering using the standalone version... (but i have no experience with that...)

 

rgds,

 

nisus