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Jeff Patton
JeffPatton


Location:
Lexington, USA

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August 2002

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14 November 2009

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May 22, 2008. 19:08
Random blurb - Car paint / Volume Caustics
Now that I have some newer PC's here, I wanted to run some animation tests to 'break them in' if you will. I started things off simple with a car paint animation. The Audi model was provided by someone else (thanks).

(click image to enlarge)


Animation:
http://jeffpatton.net/Blog-images/Audi_IM.mov

I suppose the primary point of interest here (other than the obvious homage to Iron Man) is that there is absolutely no lighting in this scene. There's no GI, FG, or even light sources for that matter. Well, there's a skylight that's turned off to ensure all lighting is disabled...So why didn't I get a black render?

If you think about it, practically everything is reflective to some extent. All materials in this scene are also reflective and when I place them into a HDR environment, they simply reflect that illumination data.

Render times? Not too bad, about 2.5 minutes per frame at 840x480 resolution. Of course it's a fairly simple scene without a 3d environment or direct/indirect illumination, but there's a TON of glossy/non-glossy reflections to calculate here.

Up next, volume caustics test:

(click image to enlarge)


Animation:
http://jeffpatton.net/Tests/Vol_caustic.mov

Mmmmm, liquid jello...

This material isn't terribly complex, but volume effects like this can be cumbersome to dial in. I used a dielectric surface shader, dielectric photon shader, parti-volume photon & parti volume...volume shaders. For what it's worth, volumetric effects work better with the updated photometric lights in 2009.
May 12, 2008. 21:28
Optimizing your scenes for mr proxies
"I'm using the new mr Proxy objects in 3ds Max 2009 / 3ds Max Design 2009 and I can't render but a few proxy objects before I run into the dreaded out of memory error....what gives?"

I've been asked this a few times, and seen it asked on various forums so I thought I'd post some information here that will help that situation.

In 3ds Max 2009 / 3ds Max Design 2009 there's a new BSP method introduced called BSP2. For those wondering, BSP = Binary Space Partitioning and it sub-divides our scenes into boxes (voxels) which allow mental ray to accelerate the ray-tracing process.
(Of course that's an over simplified explanation)

BSP vs. BSP2 (per the help file in 2009):

BSP - Fastest solution for single-processor systems. Also good for small-to-medium sized scenes (less than 1 million triangles). Offers adjustable parameters for tuning.

BSP2 - Optimized for large scenes containing more than one million triangles. Requires less memory than BSP and is able to flush memory when necessary. May produce a small performance loss when using BSP2 with smaller / less complex scenes. Adjustments are automatic here, so there are no adjustable parameters needed for tuning.

Now that you're armed with this information it becomes clear that when rendering a complex scene with a lot of mr proxies, you should switch over to BSP2. But, there's another option that you can disable that will also help: Turn off the scanline option.

The scanline option is enabled by default and it allows mental ray to use both methods of calculation to render a scene. When enabled, the scanline option handles the direct illumination (primary rays) only. As expected, raytracing handles the indirect illumination, reflections/refractions, etc.

BTW, if you turn off scanline, that doesn't mean you'll lose the direct illumination in your scene, it just means raytracing will take over that task.

So, why would we want to turn scanline off? Zap has explained that the scanline option speeds up simple scenes, but doesn't really help complex scenes that much. He also mentioned that it creates some memory consumption that isn't flushable. Therefore, turning it off on complex scenes with BSP2 will help free up some extra memory.

Cool eh? Now if anyone is asking at this point "where is all this BSP & scanline stuff you speak of located?"...here's a screen capture:

(click image to enlarge)

 
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